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SubjectRe: [PATCH v4 2/2] tty: serial: add driver for the SiFive UART
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On 4/11/19 2:02 AM, Paul Walmsley wrote:
> Add a serial driver for the SiFive UART, found on SiFive FU540 devices
> (among others).
>
> The underlying serial IP block is relatively basic, and currently does
> not support serial break detection. Further information on the IP
> block can be found in the documentation and Chisel sources:
>
> https://static.dev.sifive.com/FU540-C000-v1.0.pdf
>
> https://github.com/sifive/sifive-blocks/tree/master/src/main/scala/devices/uart
>
> This driver was written in collaboration with Wesley Terpstra
> <wesley@sifive.com>.
>
> Tested on a SiFive HiFive Unleashed A00 board, using BBL and the open-
> source FSBL (using a DT file based on what's targeted for mainline).
>
> This revision incorporates changes based on comments by Emil Renner
> Berthing <kernel@esmil.dk>.
>
> Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
> Signed-off-by: Paul Walmsley <paul@pwsan.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Jiri Slaby <jslaby@suse.com>
> Cc: Palmer Dabbelt <palmer@sifive.com>
> Cc: Wesley Terpstra <wesley@sifive.com>
> Cc: linux-serial@vger.kernel.org
> Cc: linux-riscv@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: Julia Lawall <julia.lawall@lip6.fr>
> ---
> drivers/tty/serial/Kconfig | 24 +
> drivers/tty/serial/Makefile | 1 +
> drivers/tty/serial/sifive.c | 1067 ++++++++++++++++++++++++++++++
> include/uapi/linux/serial_core.h | 3 +
> 4 files changed, 1095 insertions(+)
> create mode 100644 drivers/tty/serial/sifive.c
>
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 72966bc0ac76..561e053b690a 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -1095,6 +1095,30 @@ config SERIAL_OMAP_CONSOLE
> your boot loader about how to pass options to the kernel at
> boot time.)
>
> +config SERIAL_SIFIVE
> + tristate "SiFive UART support"
> + depends on OF
> + select SERIAL_CORE
> + help
> + Select this option if you are building a kernel for a device that
> + contains a SiFive UART IP block. This type of UART is present on
> + SiFive FU540 SoCs, among others.
> +
> +config SERIAL_SIFIVE_CONSOLE
> + bool "Console on SiFive UART"
> + depends on SERIAL_SIFIVE=y
> + select SERIAL_CORE_CONSOLE
> + help
> + Select this option if you would like to use a SiFive UART as the
> + system console.
> +
> + Even if you say Y here, the currently visible virtual console
> + (/dev/tty0) will still be used as the system console by default, but
> + you can alter that using a kernel command line option such as
> + "console=ttySIFx". (Try "man bootparam" or see the documentation of
> + your boot loader about how to pass options to the kernel at
> + boot time.)
> +
> config SERIAL_LANTIQ
> bool "Lantiq serial driver"
> depends on LANTIQ
> diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
> index 40b702aaa85e..2aff1d07d08b 100644
> --- a/drivers/tty/serial/Makefile
> +++ b/drivers/tty/serial/Makefile
> @@ -92,6 +92,7 @@ obj-$(CONFIG_SERIAL_PIC32) += pic32_uart.o
> obj-$(CONFIG_SERIAL_MPS2_UART) += mps2-uart.o
> obj-$(CONFIG_SERIAL_OWL) += owl-uart.o
> obj-$(CONFIG_SERIAL_RDA) += rda-uart.o
> +obj-$(CONFIG_SERIAL_SIFIVE) += sifive.o
>
> # GPIOLIB helpers for modem control lines
> obj-$(CONFIG_SERIAL_MCTRL_GPIO) += serial_mctrl_gpio.o
> diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c
> new file mode 100644
> index 000000000000..7401cfed0f48
> --- /dev/null
> +++ b/drivers/tty/serial/sifive.c
> @@ -0,0 +1,1067 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * SiFive UART driver
> + * Copyright (C) 2018 Paul Walmsley <paul@pwsan.com>
> + * Copyright (C) 2018 SiFive
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * Based partially on:
> + * - drivers/tty/serial/pxa.c
> + * - drivers/tty/serial/amba-pl011.c
> + * - drivers/tty/serial/uartlite.c
> + * - drivers/tty/serial/omap-serial.c
> + * - drivers/pwm/pwm-sifive.c
> + *
> + * See the following sources for further documentation:
> + * - Chapter 19 "Universal Asynchronous Receiver/Transmitter (UART)" of
> + * SiFive FE310-G000 v2p3
> + * - The tree/master/src/main/scala/devices/uart directory of
> + * https://github.com/sifive/sifive-blocks/
> + *
> + * The SiFive UART design is not 8250-compatible. The following common
> + * features are not supported:
> + * - Word lengths other than 8 bits
> + * - Break handling
> + * - Parity
> + * - Flow control
> + * - Modem signals (DSR, RI, etc.)
> + * On the other hand, the design is free from the baggage of the 8250
> + * programming model.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/console.h>
> +#include <linux/delay.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/irq.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_irq.h>
> +#include <linux/platform_device.h>
> +#include <linux/serial_core.h>
> +#include <linux/serial_reg.h>
> +#include <linux/slab.h>
> +#include <linux/tty.h>
> +#include <linux/tty_flip.h>
> +
> +/*
> + * Register offsets
> + */
> +
> +/* TXDATA */
> +#define SIFIVE_SERIAL_TXDATA_OFFS 0x0
> +#define SIFIVE_SERIAL_TXDATA_FULL_SHIFT 31
> +#define SIFIVE_SERIAL_TXDATA_FULL_MASK (1 << SIFIVE_SERIAL_TXDATA_FULL_SHIFT)
> +#define SIFIVE_SERIAL_TXDATA_DATA_SHIFT 0
> +#define SIFIVE_SERIAL_TXDATA_DATA_MASK (0xff << SIFIVE_SERIAL_TXDATA_DATA_SHIFT)
> +
> +/* RXDATA */
> +#define SIFIVE_SERIAL_RXDATA_OFFS 0x4
> +#define SIFIVE_SERIAL_RXDATA_EMPTY_SHIFT 31
> +#define SIFIVE_SERIAL_RXDATA_EMPTY_MASK (1 << SIFIVE_SERIAL_RXDATA_EMPTY_SHIFT)
> +#define SIFIVE_SERIAL_RXDATA_DATA_SHIFT 0
> +#define SIFIVE_SERIAL_RXDATA_DATA_MASK (0xff << SIFIVE_SERIAL_RXDATA_DATA_SHIFT)
> +
> +/* TXCTRL */
> +#define SIFIVE_SERIAL_TXCTRL_OFFS 0x8
> +#define SIFIVE_SERIAL_TXCTRL_TXCNT_SHIFT 16
> +#define SIFIVE_SERIAL_TXCTRL_TXCNT_MASK (0x7 << SIFIVE_SERIAL_TXCTRL_TXCNT_SHIFT)
> +#define SIFIVE_SERIAL_TXCTRL_NSTOP_SHIFT 1
> +#define SIFIVE_SERIAL_TXCTRL_NSTOP_MASK (1 << SIFIVE_SERIAL_TXCTRL_NSTOP_SHIFT)
> +#define SIFIVE_SERIAL_TXCTRL_TXEN_SHIFT 0
> +#define SIFIVE_SERIAL_TXCTRL_TXEN_MASK (1 << SIFIVE_SERIAL_TXCTRL_TXEN_SHIFT)
> +
> +/* RXCTRL */
> +#define SIFIVE_SERIAL_RXCTRL_OFFS 0xC
> +#define SIFIVE_SERIAL_RXCTRL_RXCNT_SHIFT 16
> +#define SIFIVE_SERIAL_RXCTRL_RXCNT_MASK (0x7 << SIFIVE_SERIAL_TXCTRL_TXCNT_SHIFT)
> +#define SIFIVE_SERIAL_RXCTRL_RXEN_SHIFT 0
> +#define SIFIVE_SERIAL_RXCTRL_RXEN_MASK (1 << SIFIVE_SERIAL_RXCTRL_RXEN_SHIFT)
> +
> +/* IE */
> +#define SIFIVE_SERIAL_IE_OFFS 0x10
> +#define SIFIVE_SERIAL_IE_RXWM_SHIFT 1
> +#define SIFIVE_SERIAL_IE_RXWM_MASK (1 << SIFIVE_SERIAL_IE_RXWM_SHIFT)
> +#define SIFIVE_SERIAL_IE_TXWM_SHIFT 0
> +#define SIFIVE_SERIAL_IE_TXWM_MASK (1 << SIFIVE_SERIAL_IE_TXWM_SHIFT)
> +
> +/* IP */
> +#define SIFIVE_SERIAL_IP_OFFS 0x14
> +#define SIFIVE_SERIAL_IP_RXWM_SHIFT 1
> +#define SIFIVE_SERIAL_IP_RXWM_MASK (1 << SIFIVE_SERIAL_IP_RXWM_SHIFT)
> +#define SIFIVE_SERIAL_IP_TXWM_SHIFT 0
> +#define SIFIVE_SERIAL_IP_TXWM_MASK (1 << SIFIVE_SERIAL_IP_TXWM_SHIFT)
> +
> +/* DIV */
> +#define SIFIVE_SERIAL_DIV_OFFS 0x18
> +#define SIFIVE_SERIAL_DIV_DIV_SHIFT 0
> +#define SIFIVE_SERIAL_DIV_DIV_MASK (0xffff << SIFIVE_SERIAL_IP_DIV_SHIFT)
> +
> +/*
> + * Config macros
> + */
> +
> +/*
> + * SIFIVE_SERIAL_MAX_PORTS: maximum number of UARTs on a device that can
> + * host a serial console
> + */
> +#define SIFIVE_SERIAL_MAX_PORTS 8
> +
> +/*
> + * SIFIVE_DEFAULT_BAUD_RATE: default baud rate that the driver should
> + * configure itself to use
> + */
> +#define SIFIVE_DEFAULT_BAUD_RATE 115200
> +
> +/* SIFIVE_SERIAL_NAME: our driver's name that we pass to the operating system */
> +#define SIFIVE_SERIAL_NAME "sifive-serial"
> +
> +/* SIFIVE_TTY_PREFIX: tty name prefix for SiFive serial ports */
> +#define SIFIVE_TTY_PREFIX "ttySIF"
> +
> +/* SIFIVE_TX_FIFO_DEPTH: depth of the TX FIFO (in bytes) */
> +#define SIFIVE_TX_FIFO_DEPTH 8
> +
> +/* SIFIVE_RX_FIFO_DEPTH: depth of the TX FIFO (in bytes) */
> +#define SIFIVE_RX_FIFO_DEPTH 8
> +
> +#if (SIFIVE_TX_FIFO_DEPTH != SIFIVE_RX_FIFO_DEPTH)
> +#error Driver does not support configurations with different TX, RX FIFO sizes
> +#endif
> +
> +/*
> + *
> + */
> +

Remove it if no comment here ?

Regards,
Atish
> +/**
> + * sifive_serial_port - driver-specific data extension to struct uart_port
> + * @port: struct uart_port embedded in this struct
> + * @dev: struct device *
> + * @ier: shadowed copy of the interrupt enable register
> + * @clkin_rate: input clock to the UART IP block.
> + * @baud_rate: UART serial line rate (e.g., 115200 baud)
> + * @clk_notifier: clock rate change notifier for upstream clock changes
> + *
> + * Configuration data specific to this SiFive UART.
> + */
> +struct sifive_serial_port {
> + struct uart_port port;
> + struct device *dev;
> + unsigned char ier;
> + unsigned long clkin_rate;
> + unsigned long baud_rate;
> + struct clk *clk;
> + struct notifier_block clk_notifier;
> +};
> +
> +/*
> + * Structure container-of macros
> + */
> +
> +#define port_to_sifive_serial_port(p) (container_of((p), \
> + struct sifive_serial_port, \
> + port))
> +
> +#define notifier_to_sifive_serial_port(nb) (container_of((nb), \
> + struct sifive_serial_port, \
> + clk_notifier))
> +
> +/*
> + * Forward declarations
> + */
> +static void sifive_serial_stop_tx(struct uart_port *port);
> +
> +/*
> + * Internal functions
> + */
> +
> +/**
> + * __ssp_early_writel() - write to a SiFive serial port register (early)
> + * @port: pointer to a struct uart_port record
> + * @offs: register address offset from the IP block base address
> + * @v: value to write to the register
> + *
> + * Given a pointer @port to a struct uart_port record, write the value
> + * @v to the IP block register address offset @offs. This function is
> + * intended for early console use.
> + *
> + * Context: Intended to be used only by the earlyconsole code.
> + */
> +static void __ssp_early_writel(u32 v, u16 offs, struct uart_port *port)
> +{
> + writel_relaxed(v, port->membase + offs);
> +}
> +
> +/**
> + * __ssp_early_readl() - read from a SiFive serial port register (early)
> + * @port: pointer to a struct uart_port record
> + * @offs: register address offset from the IP block base address
> + *
> + * Given a pointer @port to a struct uart_port record, read the
> + * contents of the IP block register located at offset @offs from the
> + * IP block base and return it. This function is intended for early
> + * console use.
> + *
> + * Context: Intended to be called only by the earlyconsole code or by
> + * __ssp_readl() or __ssp_writel() (in this driver)
> + *
> + * Returns: the register value read from the UART.
> + */
> +static u32 __ssp_early_readl(struct uart_port *port, u16 offs)
> +{
> + return readl_relaxed(port->membase + offs);
> +}
> +
> +/**
> + * __ssp_writel() - write to a SiFive serial port register
> + * @v: value to write to the register
> + * @offs: register address offset from the IP block base address
> + * @ssp: pointer to a struct sifive_serial_port record
> + *
> + * Write the value @v to the IP block register located at offset @offs from the
> + * IP block base, given a pointer @ssp to a struct sifive_serial_port record.
> + *
> + * Context: Any context.
> + */
> +static void __ssp_writel(u32 v, u16 offs, struct sifive_serial_port *ssp)
> +{
> + __ssp_early_writel(v, offs, &ssp->port);
> +}
> +
> +/**
> + * __ssp_readl() - read from a SiFive serial port register
> + * @ssp: pointer to a struct sifive_serial_port record
> + * @offs: register address offset from the IP block base address
> + *
> + * Read the contents of the IP block register located at offset @offs from the
> + * IP block base, given a pointer @ssp to a struct sifive_serial_port record.
> + *
> + * Context: Any context.
> + *
> + * Returns: the value of the UART register
> + */
> +static u32 __ssp_readl(struct sifive_serial_port *ssp, u16 offs)
> +{
> + return __ssp_early_readl(&ssp->port, offs);
> +}
> +
> +/**
> + * sifive_serial_is_txfifo_full() - is the TXFIFO full?
> + * @ssp: pointer to a struct sifive_serial_port
> + *
> + * Read the transmit FIFO "full" bit, returning a non-zero value if the
> + * TX FIFO is full, or zero if space remains. Intended to be used to prevent
> + * writes to the TX FIFO when it's full.
> + *
> + * Returns: SIFIVE_SERIAL_TXDATA_FULL_MASK (non-zero) if the transmit FIFO
> + * is full, or 0 if space remains.
> + */
> +static int sifive_serial_is_txfifo_full(struct sifive_serial_port *ssp)
> +{
> + return __ssp_readl(ssp, SIFIVE_SERIAL_TXDATA_OFFS) &
> + SIFIVE_SERIAL_TXDATA_FULL_MASK;
> +}
> +
> +/**
> + * __ssp_transmit_char() - enqueue a byte to transmit onto the TX FIFO
> + * @ssp: pointer to a struct sifive_serial_port
> + * @ch: character to transmit
> + *
> + * Enqueue a byte @ch onto the transmit FIFO, given a pointer @ssp to the
> + * struct sifive_serial_port * to transmit on. Caller should first check to
> + * ensure that the TXFIFO has space; see sifive_serial_is_txfifo_full().
> + *
> + * Context: Any context.
> + */
> +static void __ssp_transmit_char(struct sifive_serial_port *ssp, int ch)
> +{
> + __ssp_writel(ch, SIFIVE_SERIAL_TXDATA_OFFS, ssp);
> +}
> +
> +/**
> + * __ssp_transmit_chars() - enqueue multiple bytes onto the TX FIFO
> + * @ssp: pointer to a struct sifive_serial_port
> + *
> + * Transfer up to a TX FIFO size's worth of characters from the Linux serial
> + * transmit buffer to the SiFive UART TX FIFO.
> + *
> + * Context: Any context. Expects @ssp->port.lock to be held by caller.
> + */
> +static void __ssp_transmit_chars(struct sifive_serial_port *ssp)
> +{
> + struct circ_buf *xmit = &ssp->port.state->xmit;
> + int count;
> +
> + if (ssp->port.x_char) {
> + __ssp_transmit_char(ssp, ssp->port.x_char);
> + ssp->port.icount.tx++;
> + ssp->port.x_char = 0;
> + return;
> + }
> + if (uart_circ_empty(xmit) || uart_tx_stopped(&ssp->port)) {
> + sifive_serial_stop_tx(&ssp->port);
> + return;
> + }
> + count = SIFIVE_TX_FIFO_DEPTH;
> + do {
> + __ssp_transmit_char(ssp, xmit->buf[xmit->tail]);
> + xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
> + ssp->port.icount.tx++;
> + if (uart_circ_empty(xmit))
> + break;
> + } while (--count > 0);
> +
> + if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
> + uart_write_wakeup(&ssp->port);
> +
> + if (uart_circ_empty(xmit))
> + sifive_serial_stop_tx(&ssp->port);
> +}
> +
> +/**
> + * __ssp_enable_txwm() - enable transmit watermark interrupts
> + * @ssp: pointer to a struct sifive_serial_port
> + *
> + * Enable interrupt generation when the transmit FIFO watermark is reached
> + * on the SiFive UART referred to by @ssp.
> + */
> +static void __ssp_enable_txwm(struct sifive_serial_port *ssp)
> +{
> + if (ssp->ier & SIFIVE_SERIAL_IE_TXWM_MASK)
> + return;
> +
> + ssp->ier |= SIFIVE_SERIAL_IE_TXWM_MASK;
> + __ssp_writel(ssp->ier, SIFIVE_SERIAL_IE_OFFS, ssp);
> +}
> +
> +/**
> + * __ssp_enable_rxwm() - enable receive watermark interrupts
> + * @ssp: pointer to a struct sifive_serial_port
> + *
> + * Enable interrupt generation when the receive FIFO watermark is reached
> + * on the SiFive UART referred to by @ssp.
> + */
> +static void __ssp_enable_rxwm(struct sifive_serial_port *ssp)
> +{
> + if (ssp->ier & SIFIVE_SERIAL_IE_RXWM_MASK)
> + return;
> +
> + ssp->ier |= SIFIVE_SERIAL_IE_RXWM_MASK;
> + __ssp_writel(ssp->ier, SIFIVE_SERIAL_IE_OFFS, ssp);
> +}
> +
> +/**
> + * __ssp_disable_txwm() - disable transmit watermark interrupts
> + * @ssp: pointer to a struct sifive_serial_port
> + *
> + * Disable interrupt generation when the transmit FIFO watermark is reached
> + * on the UART referred to by @ssp.
> + */
> +static void __ssp_disable_txwm(struct sifive_serial_port *ssp)
> +{
> + if (!(ssp->ier & SIFIVE_SERIAL_IE_TXWM_MASK))
> + return;
> +
> + ssp->ier &= ~SIFIVE_SERIAL_IE_TXWM_MASK;
> + __ssp_writel(ssp->ier, SIFIVE_SERIAL_IE_OFFS, ssp);
> +}
> +
> +/**
> + * __ssp_disable_rxwm() - disable receive watermark interrupts
> + * @ssp: pointer to a struct sifive_serial_port
> + *
> + * Disable interrupt generation when the receive FIFO watermark is reached
> + * on the UART referred to by @ssp.
> + */
> +static void __ssp_disable_rxwm(struct sifive_serial_port *ssp)
> +{
> + if (!(ssp->ier & SIFIVE_SERIAL_IE_RXWM_MASK))
> + return;
> +
> + ssp->ier &= ~SIFIVE_SERIAL_IE_RXWM_MASK;
> + __ssp_writel(ssp->ier, SIFIVE_SERIAL_IE_OFFS, ssp);
> +}
> +
> +/**
> + * __ssp_receive_char() - receive a byte from the UART
> + * @ssp: pointer to a struct sifive_serial_port
> + * @is_empty: char pointer to return whether the RX FIFO is empty
> + *
> + * Try to read a byte from the SiFive UART RX FIFO, referenced by
> + * @ssp, and to return it. Also returns the RX FIFO empty bit in
> + * the char pointed to by @ch. The caller must pass the byte back to the
> + * Linux serial layer if needed.
> + *
> + * Returns: the byte read from the UART RX FIFO.
> + */
> +static char __ssp_receive_char(struct sifive_serial_port *ssp, char *is_empty)
> +{
> + u32 v;
> + u8 ch;
> +
> + v = __ssp_readl(ssp, SIFIVE_SERIAL_RXDATA_OFFS);
> +
> + if (!is_empty)
> + WARN_ON(1);
> + else
> + *is_empty = (v & SIFIVE_SERIAL_RXDATA_EMPTY_MASK) >>
> + SIFIVE_SERIAL_RXDATA_EMPTY_SHIFT;
> +
> + ch = (v & SIFIVE_SERIAL_RXDATA_DATA_MASK) >>
> + SIFIVE_SERIAL_RXDATA_DATA_SHIFT;
> +
> + return ch;
> +}
> +
> +/**
> + * __ssp_receive_chars() - receive multiple bytes from the UART
> + * @ssp: pointer to a struct sifive_serial_port
> + *
> + * Receive up to an RX FIFO's worth of bytes from the SiFive UART referred
> + * to by @ssp and pass them up to the Linux serial layer.
> + *
> + * Context: Expects ssp->port.lock to be held by caller.
> + */
> +static void __ssp_receive_chars(struct sifive_serial_port *ssp)
> +{
> + unsigned char ch;
> + char is_empty;
> + int c;
> +
> + for (c = SIFIVE_RX_FIFO_DEPTH; c > 0; --c) {
> + ch = __ssp_receive_char(ssp, &is_empty);
> + if (is_empty)
> + break;
> +
> + ssp->port.icount.rx++;
> + uart_insert_char(&ssp->port, 0, 0, ch, TTY_NORMAL);
> + }
> +
> + spin_unlock(&ssp->port.lock);
> + tty_flip_buffer_push(&ssp->port.state->port);
> + spin_lock(&ssp->port.lock);
> +}
> +
> +/**
> + * __ssp_update_div() - calculate the divisor setting by the line rate
> + * @ssp: pointer to a struct sifive_serial_port
> + *
> + * Calculate the appropriate value of the clock divisor for the UART
> + * and target line rate referred to by @ssp and write it into the
> + * hardware.
> + */
> +static void __ssp_update_div(struct sifive_serial_port *ssp)
> +{
> + u16 div;
> +
> + div = DIV_ROUND_UP(ssp->clkin_rate, ssp->baud_rate) - 1;
> +
> + __ssp_writel(div, SIFIVE_SERIAL_DIV_OFFS, ssp);
> +}
> +
> +/**
> + * __ssp_update_baud_rate() - set the UART "baud rate"
> + * @ssp: pointer to a struct sifive_serial_port
> + * @rate: new target bit rate
> + *
> + * Calculate the UART divisor value for the target bit rate @rate for the
> + * SiFive UART described by @ssp and program it into the UART. There may
> + * be some error between the target bit rate and the actual bit rate implemented
> + * by the UART due to clock ratio granularity.
> + */
> +static void __ssp_update_baud_rate(struct sifive_serial_port *ssp,
> + unsigned int rate)
> +{
> + if (ssp->baud_rate == rate)
> + return;
> +
> + ssp->baud_rate = rate;
> + __ssp_update_div(ssp);
> +}
> +
> +/**
> + * __ssp_set_stop_bits() - set the number of stop bits
> + * @ssp: pointer to a struct sifive_serial_port
> + * @nstop: 1 or 2 (stop bits)
> + *
> + * Program the SiFive UART referred to by @ssp to use @nstop stop bits.
> + */
> +static void __ssp_set_stop_bits(struct sifive_serial_port *ssp, char nstop)
> +{
> + u32 v;
> +
> + if (nstop < 1 || nstop > 2) {
> + WARN_ON(1);
> + return;
> + }
> +
> + v = __ssp_readl(ssp, SIFIVE_SERIAL_TXCTRL_OFFS);
> + v &= ~SIFIVE_SERIAL_TXCTRL_NSTOP_MASK;
> + v |= (nstop - 1) << SIFIVE_SERIAL_TXCTRL_NSTOP_SHIFT;
> + __ssp_writel(v, SIFIVE_SERIAL_TXCTRL_OFFS, ssp);
> +}
> +
> +/**
> + * __ssp_wait_for_xmitr() - wait for an empty slot on the TX FIFO
> + * @ssp: pointer to a struct sifive_serial_port
> + *
> + * Delay while the UART TX FIFO referred to by @ssp is marked as full.
> + *
> + * Context: Any context.
> + */
> +static void __maybe_unused __ssp_wait_for_xmitr(struct sifive_serial_port *ssp)
> +{
> + while (sifive_serial_is_txfifo_full(ssp))
> + udelay(1); /* XXX Could probably be more intelligent here */
> +}
> +
> +/*
> + * Linux serial API functions
> + */
> +
> +static void sifive_serial_stop_tx(struct uart_port *port)
> +{
> + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
> +
> + __ssp_disable_txwm(ssp);
> +}
> +
> +static void sifive_serial_stop_rx(struct uart_port *port)
> +{
> + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
> +
> + __ssp_disable_rxwm(ssp);
> +}
> +
> +static void sifive_serial_start_tx(struct uart_port *port)
> +{
> + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
> +
> + __ssp_enable_txwm(ssp);
> +}
> +
> +static irqreturn_t sifive_serial_irq(int irq, void *dev_id)
> +{
> + struct sifive_serial_port *ssp = dev_id;
> + u32 ip;
> +
> + spin_lock(&ssp->port.lock);
> +
> + ip = __ssp_readl(ssp, SIFIVE_SERIAL_IP_OFFS);
> + if (!ip) {
> + spin_unlock(&ssp->port.lock);
> + return IRQ_NONE;
> + }
> +
> + if (ip & SIFIVE_SERIAL_IP_RXWM_MASK)
> + __ssp_receive_chars(ssp);
> + if (ip & SIFIVE_SERIAL_IP_TXWM_MASK)
> + __ssp_transmit_chars(ssp);
> +
> + spin_unlock(&ssp->port.lock);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static unsigned int sifive_serial_tx_empty(struct uart_port *port)
> +{
> + return TIOCSER_TEMT;
> +}
> +
> +static unsigned int sifive_serial_get_mctrl(struct uart_port *port)
> +{
> + return TIOCM_CAR | TIOCM_CTS | TIOCM_DSR;
> +}
> +
> +static void sifive_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
> +{
> + /* IP block does not support these signals */
> +}
> +
> +static void sifive_serial_break_ctl(struct uart_port *port, int break_state)
> +{
> + /* IP block does not support sending a break */
> +}
> +
> +static int sifive_serial_startup(struct uart_port *port)
> +{
> + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
> +
> + __ssp_enable_rxwm(ssp);
> +
> + return 0;
> +}
> +
> +static void sifive_serial_shutdown(struct uart_port *port)
> +{
> + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
> +
> + __ssp_disable_rxwm(ssp);
> + __ssp_disable_txwm(ssp);
> +}
> +
> +/**
> + * sifive_serial_clk_notifier() - clock post-rate-change notifier
> + * @nb: pointer to the struct notifier_block, from the notifier code
> + * @event: event mask from the notifier code
> + * @data: pointer to the struct clk_notifier_data from the notifier code
> + *
> + * On the V0 SoC, the UART IP block is derived from the CPU clock source
> + * after a synchronous divide-by-two divider, so any CPU clock rate change
> + * requires the UART baud rate to be updated. This presumably could corrupt any
> + * serial word currently being transmitted or received. It would probably
> + * be better to stop receives and transmits, then complete the baud rate
> + * change, then re-enable them.
> + */
> +static int sifive_serial_clk_notifier(struct notifier_block *nb,
> + unsigned long event, void *data)
> +{
> + struct clk_notifier_data *cnd = data;
> + struct sifive_serial_port *ssp = notifier_to_sifive_serial_port(nb);
> +
> + if (event == POST_RATE_CHANGE && ssp->clkin_rate != cnd->new_rate) {
> + ssp->clkin_rate = cnd->new_rate;
> + __ssp_update_div(ssp);
> + }
> +
> + return NOTIFY_OK;
> +}
> +
> +static void sifive_serial_set_termios(struct uart_port *port,
> + struct ktermios *termios,
> + struct ktermios *old)
> +{
> + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
> + unsigned long flags;
> + u32 v, old_v;
> + int rate;
> + char nstop;
> +
> + if ((termios->c_cflag & CSIZE) != CS8) {
> + dev_err(ssp->port.dev, "only 8-bit words supported\n");
> + return;
> + }
> +
> + /* Set number of stop bits */
> + nstop = (termios->c_cflag & CSTOPB) ? 2 : 1;
> + __ssp_set_stop_bits(ssp, nstop);
> +
> + /* Set line rate */
> + rate = uart_get_baud_rate(port, termios, old, 0, ssp->clkin_rate / 16);
> + __ssp_update_baud_rate(ssp, rate);
> +
> + spin_lock_irqsave(&ssp->port.lock, flags);
> +
> + /*
> + * Update the per-port timeout.
> + */
> + uart_update_timeout(port, termios->c_cflag, rate);
> +
> + ssp->port.read_status_mask = 0;
> + if (termios->c_iflag & INPCK) {
> + dev_err(ssp->port.dev, "INPCK flag not supported\n");
> + goto ssst_out;
> + }
> + if (termios->c_iflag & (BRKINT | PARMRK)) {
> + dev_err(ssp->port.dev, "BRKINT/PARMRK flag not supported\n");
> + goto ssst_out;
> + }
> +
> + /*
> + * ignore all characters if CREAD is not set
> + */
> + v = __ssp_readl(ssp, SIFIVE_SERIAL_RXCTRL_OFFS);
> + old_v = v;
> + if ((termios->c_cflag & CREAD) == 0)
> + v &= SIFIVE_SERIAL_RXCTRL_RXEN_MASK;
> + else
> + v |= SIFIVE_SERIAL_RXCTRL_RXEN_MASK;
> + if (v != old_v)
> + __ssp_writel(v, SIFIVE_SERIAL_RXCTRL_OFFS, ssp);
> +
> +ssst_out:
> + spin_unlock_irqrestore(&ssp->port.lock, flags);
> +}
> +
> +static void sifive_serial_release_port(struct uart_port *port)
> +{
> +}
> +
> +static int sifive_serial_request_port(struct uart_port *port)
> +{
> + return 0;
> +}
> +
> +static void sifive_serial_config_port(struct uart_port *port, int flags)
> +{
> + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
> +
> + ssp->port.type = PORT_SIFIVE_V0;
> +}
> +
> +static int sifive_serial_verify_port(struct uart_port *port,
> + struct serial_struct *ser)
> +{
> + return -EINVAL;
> +}
> +
> +static const char *sifive_serial_type(struct uart_port *port)
> +{
> + return port->type == PORT_SIFIVE_V0 ? "SiFive UART v0" : NULL;
> +}
> +
> +/*
> + * Early console support
> + */
> +
> +#ifdef CONFIG_SERIAL_EARLYCON
> +static void early_sifive_serial_putc(struct uart_port *port, int c)
> +{
> + while (__ssp_early_readl(port, SIFIVE_SERIAL_TXDATA_OFFS) &
> + SIFIVE_SERIAL_TXDATA_FULL_MASK)
> + cpu_relax();
> +
> + __ssp_early_writel(c, SIFIVE_SERIAL_TXDATA_OFFS, port);
> +}
> +
> +static void early_sifive_serial_write(struct console *con, const char *s,
> + unsigned int n)
> +{
> + struct earlycon_device *dev = con->data;
> + struct uart_port *port = &dev->port;
> +
> + uart_console_write(port, s, n, early_sifive_serial_putc);
> +}
> +
> +static int __init early_sifive_serial_setup(struct earlycon_device *dev,
> + const char *options)
> +{
> + struct uart_port *port = &dev->port;
> +
> + if (!port->membase)
> + return -ENODEV;
> +
> + dev->con->write = early_sifive_serial_write;
> +
> + return 0;
> +}
> +
> +OF_EARLYCON_DECLARE(sifive, "sifive,uart0", early_sifive_serial_setup);
> +OF_EARLYCON_DECLARE(sifive, "sifive,fu540-c000-uart0",
> + early_sifive_serial_setup);
> +#endif /* CONFIG_SERIAL_EARLYCON */
> +
> +/*
> + * Linux console interface
> + */
> +
> +#ifdef CONFIG_SERIAL_SIFIVE_CONSOLE
> +
> +static struct sifive_serial_port *sifive_serial_console_ports[SIFIVE_SERIAL_MAX_PORTS];
> +
> +static void sifive_serial_console_putchar(struct uart_port *port, int ch)
> +{
> + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
> +
> + __ssp_wait_for_xmitr(ssp);
> + __ssp_transmit_char(ssp, ch);
> +}
> +
> +static void sifive_serial_console_write(struct console *co, const char *s,
> + unsigned int count)
> +{
> + struct sifive_serial_port *ssp = sifive_serial_console_ports[co->index];
> + unsigned long flags;
> + unsigned int ier;
> + int locked = 1;
> +
> + if (!ssp)
> + return;
> +
> + local_irq_save(flags);
> + if (ssp->port.sysrq)
> + locked = 0;
> + else if (oops_in_progress)
> + locked = spin_trylock(&ssp->port.lock);
> + else
> + spin_lock(&ssp->port.lock);
> +
> + ier = __ssp_readl(ssp, SIFIVE_SERIAL_IE_OFFS);
> + __ssp_writel(0, SIFIVE_SERIAL_IE_OFFS, ssp);
> +
> + uart_console_write(&ssp->port, s, count, sifive_serial_console_putchar);
> +
> + __ssp_writel(ier, SIFIVE_SERIAL_IE_OFFS, ssp);
> +
> + if (locked)
> + spin_unlock(&ssp->port.lock);
> + local_irq_restore(flags);
> +}
> +
> +static int __init sifive_serial_console_setup(struct console *co, char *options)
> +{
> + struct sifive_serial_port *ssp;
> + int baud = SIFIVE_DEFAULT_BAUD_RATE;
> + int bits = 8;
> + int parity = 'n';
> + int flow = 'n';
> +
> + if (co->index < 0 || co->index >= SIFIVE_SERIAL_MAX_PORTS)
> + return -ENODEV;
> +
> + ssp = sifive_serial_console_ports[co->index];
> + if (!ssp)
> + return -ENODEV;
> +
> + if (options)
> + uart_parse_options(options, &baud, &parity, &bits, &flow);
> +
> + return uart_set_options(&ssp->port, co, baud, parity, bits, flow);
> +}
> +
> +static struct uart_driver sifive_serial_uart_driver;
> +
> +static struct console sifive_serial_console = {
> + .name = SIFIVE_TTY_PREFIX,
> + .write = sifive_serial_console_write,
> + .device = uart_console_device,
> + .setup = sifive_serial_console_setup,
> + .flags = CON_PRINTBUFFER,
> + .index = -1,
> + .data = &sifive_serial_uart_driver,
> +};
> +
> +static int __init sifive_console_init(void)
> +{
> + register_console(&sifive_serial_console);
> + return 0;
> +}
> +
> +console_initcall(sifive_console_init);
> +
> +static void __ssp_add_console_port(struct sifive_serial_port *ssp)
> +{
> + sifive_serial_console_ports[ssp->port.line] = ssp;
> +}
> +
> +static void __ssp_remove_console_port(struct sifive_serial_port *ssp)
> +{
> + sifive_serial_console_ports[ssp->port.line] = 0;
> +}
> +
> +#define SIFIVE_SERIAL_CONSOLE (&sifive_serial_console)
> +
> +#else
> +
> +#define SIFIVE_SERIAL_CONSOLE NULL
> +
> +static void __ssp_add_console_port(struct sifive_serial_port *ssp)
> +{}
> +static void __ssp_remove_console_port(struct sifive_serial_port *ssp)
> +{}
> +
> +#endif
> +
> +static const struct uart_ops sifive_serial_uops = {
> + .tx_empty = sifive_serial_tx_empty,
> + .set_mctrl = sifive_serial_set_mctrl,
> + .get_mctrl = sifive_serial_get_mctrl,
> + .stop_tx = sifive_serial_stop_tx,
> + .start_tx = sifive_serial_start_tx,
> + .stop_rx = sifive_serial_stop_rx,
> + .break_ctl = sifive_serial_break_ctl,
> + .startup = sifive_serial_startup,
> + .shutdown = sifive_serial_shutdown,
> + .set_termios = sifive_serial_set_termios,
> + .type = sifive_serial_type,
> + .release_port = sifive_serial_release_port,
> + .request_port = sifive_serial_request_port,
> + .config_port = sifive_serial_config_port,
> + .verify_port = sifive_serial_verify_port,
> +};
> +
> +static struct uart_driver sifive_serial_uart_driver = {
> + .owner = THIS_MODULE,
> + .driver_name = SIFIVE_SERIAL_NAME,
> + .dev_name = SIFIVE_TTY_PREFIX,
> + .nr = SIFIVE_SERIAL_MAX_PORTS,
> + .cons = SIFIVE_SERIAL_CONSOLE,
> +};
> +
> +static int sifive_serial_probe(struct platform_device *pdev)
> +{
> + struct sifive_serial_port *ssp;
> + struct resource *mem;
> + struct clk *clk;
> + void __iomem *base;
> + int irq, id, r;
> +
> + irq = platform_get_irq(pdev, 0);
> + if (irq < 0) {
> + dev_err(&pdev->dev, "could not acquire interrupt\n");
> + return -EPROBE_DEFER;
> + }
> +
> + mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + base = devm_ioremap_resource(&pdev->dev, mem);
> + if (IS_ERR(base)) {
> + dev_err(&pdev->dev, "could not acquire device memory\n");
> + return PTR_ERR(base);
> + }
> +
> + clk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(clk)) {
> + dev_err(&pdev->dev, "unable to find controller clock\n");
> + return PTR_ERR(clk);
> + }
> +
> + id = of_alias_get_id(pdev->dev.of_node, "serial");
> + if (id < 0) {
> + dev_err(&pdev->dev, "missing aliases entry\n");
> + return id;
> + }
> +
> +#ifdef CONFIG_SERIAL_SIFIVE_CONSOLE
> + if (id > SIFIVE_SERIAL_MAX_PORTS) {
> + dev_err(&pdev->dev, "too many UARTs (%d)\n", id);
> + return -EINVAL;
> + }
> +#endif
> +
> + ssp = devm_kzalloc(&pdev->dev, sizeof(*ssp), GFP_KERNEL);
> + if (!ssp)
> + return -ENOMEM;
> +
> + ssp->port.dev = &pdev->dev;
> + ssp->port.type = PORT_SIFIVE_V0;
> + ssp->port.iotype = UPIO_MEM;
> + ssp->port.irq = irq;
> + ssp->port.fifosize = SIFIVE_TX_FIFO_DEPTH;
> + ssp->port.ops = &sifive_serial_uops;
> + ssp->port.line = id;
> + ssp->port.mapbase = mem->start;
> + ssp->port.membase = base;
> + ssp->dev = &pdev->dev;
> + ssp->clk = clk;
> + ssp->clk_notifier.notifier_call = sifive_serial_clk_notifier;
> +
> + r = clk_notifier_register(ssp->clk, &ssp->clk_notifier);
> + if (r) {
> + dev_err(&pdev->dev, "could not register clock notifier: %d\n",
> + r);
> + goto probe_out1;
> + }
> +
> + /* Set up clock divider */
> + ssp->clkin_rate = clk_get_rate(ssp->clk);
> + ssp->baud_rate = SIFIVE_DEFAULT_BAUD_RATE;
> + __ssp_update_div(ssp);
> +
> + platform_set_drvdata(pdev, ssp);
> +
> + /* Enable transmits and set the watermark level to 1 */
> + __ssp_writel((1 << SIFIVE_SERIAL_TXCTRL_TXCNT_SHIFT) |
> + SIFIVE_SERIAL_TXCTRL_TXEN_MASK,
> + SIFIVE_SERIAL_TXCTRL_OFFS, ssp);
> +
> + /* Enable receives and set the watermark level to 0 */
> + __ssp_writel((0 << SIFIVE_SERIAL_RXCTRL_RXCNT_SHIFT) |
> + SIFIVE_SERIAL_RXCTRL_RXEN_MASK,
> + SIFIVE_SERIAL_RXCTRL_OFFS, ssp);
> +
> + r = request_irq(ssp->port.irq, sifive_serial_irq, ssp->port.irqflags,
> + dev_name(&pdev->dev), ssp);
> + if (r) {
> + dev_err(&pdev->dev, "could not attach interrupt: %d\n", r);
> + goto probe_out2;
> + }
> +
> + __ssp_add_console_port(ssp);
> +
> + r = uart_add_one_port(&sifive_serial_uart_driver, &ssp->port);
> + if (r != 0) {
> + dev_err(&pdev->dev, "could not add uart: %d\n", r);
> + goto probe_out3;
> + }
> +
> + return 0;
> +
> +probe_out3:
> + __ssp_remove_console_port(ssp);
> + free_irq(ssp->port.irq, ssp);
> +probe_out2:
> + clk_notifier_unregister(ssp->clk, &ssp->clk_notifier);
> +probe_out1:
> + return r;
> +}
> +
> +static int sifive_serial_remove(struct platform_device *dev)
> +{
> + struct sifive_serial_port *ssp = platform_get_drvdata(dev);
> +
> + __ssp_remove_console_port(ssp);
> + uart_remove_one_port(&sifive_serial_uart_driver, &ssp->port);
> + free_irq(ssp->port.irq, ssp);
> + clk_notifier_unregister(ssp->clk, &ssp->clk_notifier);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id sifive_serial_of_match[] = {
> + { .compatible = "sifive,fu540-c000-uart0" },
> + { .compatible = "sifive,uart0" },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, sifive_serial_of_match);
> +
> +static struct platform_driver sifive_serial_platform_driver = {
> + .probe = sifive_serial_probe,
> + .remove = sifive_serial_remove,
> + .driver = {
> + .name = SIFIVE_SERIAL_NAME,
> + .of_match_table = of_match_ptr(sifive_serial_of_match),
> + },
> +};
> +
> +static int __init sifive_serial_init(void)
> +{
> + int r;
> +
> + r = uart_register_driver(&sifive_serial_uart_driver);
> + if (r)
> + goto init_out1;
> +
> + r = platform_driver_register(&sifive_serial_platform_driver);
> + if (r)
> + goto init_out2;
> +
> + return 0;
> +
> +init_out2:
> + uart_unregister_driver(&sifive_serial_uart_driver);
> +init_out1:
> + return r;
> +}
> +
> +static void __exit sifive_serial_exit(void)
> +{
> + platform_driver_unregister(&sifive_serial_platform_driver);
> + uart_unregister_driver(&sifive_serial_uart_driver);
> +}
> +
> +module_init(sifive_serial_init);
> +module_exit(sifive_serial_exit);
> +
> +MODULE_DESCRIPTION("SiFive UART serial driver");
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Paul Walmsley <paul@pwsan.com>");
> diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
> index 6009ee2c2e99..2191fa691770 100644
> --- a/include/uapi/linux/serial_core.h
> +++ b/include/uapi/linux/serial_core.h
> @@ -287,4 +287,7 @@
> /* RDA UART */
> #define PORT_RDA 118
>
> +/* SiFive UART */
> +#define PORT_SIFIVE_V0 119
> +
> #endif /* _UAPILINUX_SERIAL_CORE_H */
>

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