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Subject[PATCH v4 3/3] i2c: at91: added slave mode support
Date
From: Juergen Fitschen <jfi@ssv-embedded.de>

Slave mode driver is based on the concept of i2c-designware driver.

Signed-off-by: Juergen Fitschen <me@jue.yt>
[ludovic.desroches@microchip.com: rework Kconfig]
Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>
---
drivers/i2c/busses/Kconfig | 13 +++
drivers/i2c/busses/Makefile | 3 +
drivers/i2c/busses/i2c-at91-core.c | 13 ++-
drivers/i2c/busses/i2c-at91-slave.c | 147 ++++++++++++++++++++++++++++
drivers/i2c/busses/i2c-at91.h | 30 +++++-
5 files changed, 202 insertions(+), 4 deletions(-)
create mode 100644 drivers/i2c/busses/i2c-at91-slave.c

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index f2c681971201..6b1f6dcdf533 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -387,6 +387,19 @@ config I2C_AT91
the latency to fill the transmission register is too long. If you
are facing this situation, use the i2c-gpio driver.

+config I2C_AT91_SLAVE_EXPERIMENTAL
+ tristate "Microchip AT91 I2C experimental slave mode"
+ depends on I2C_AT91
+ select I2C_SLAVE
+ help
+ If you say yes to this option, support for the slave mode will be
+ added. Caution: do not use it for production. This feature has not
+ been tested in a heavy way, help wanted.
+ There are known bugs:
+ - It can hang, on a SAMA5D4, after several transfers.
+ - There are some mismtaches with a SAMA5D4 as slave and a SAMA5D2 as
+ master.
+
config I2C_AU1550
tristate "Au1550/Au1200/Au1300 SMBus interface"
depends on MIPS_ALCHEMY
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index ea75a777940e..59b22fbef90a 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -36,6 +36,9 @@ obj-$(CONFIG_I2C_ALTERA) += i2c-altera.o
obj-$(CONFIG_I2C_ASPEED) += i2c-aspeed.o
obj-$(CONFIG_I2C_AT91) += i2c-at91.o
i2c-at91-objs := i2c-at91-core.o i2c-at91-master.o
+ifeq ($(CONFIG_I2C_AT91_SLAVE_EXPERIMENTAL),y)
+ i2c-at91-objs += i2c-at91-slave.o
+endif
obj-$(CONFIG_I2C_AU1550) += i2c-au1550.o
obj-$(CONFIG_I2C_AXXIA) += i2c-axxia.o
obj-$(CONFIG_I2C_BCM2835) += i2c-bcm2835.o
diff --git a/drivers/i2c/busses/i2c-at91-core.c b/drivers/i2c/busses/i2c-at91-core.c
index 5d9c6c81e6ab..c74283fa567f 100644
--- a/drivers/i2c/busses/i2c-at91-core.c
+++ b/drivers/i2c/busses/i2c-at91-core.c
@@ -60,8 +60,10 @@ void at91_init_twi_bus(struct at91_twi_dev *dev)
{
at91_disable_twi_interrupts(dev);
at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SWRST);
-
- at91_init_twi_bus_master(dev);
+ if (dev->slave_detected)
+ at91_init_twi_bus_slave(dev);
+ else
+ at91_init_twi_bus_master(dev);
}

static struct at91_twi_pdata at91rm9200_config = {
@@ -243,7 +245,12 @@ static int at91_twi_probe(struct platform_device *pdev)
dev->adapter.timeout = AT91_I2C_TIMEOUT;
dev->adapter.dev.of_node = pdev->dev.of_node;

- rc = at91_twi_probe_master(pdev, phy_addr, dev);
+ dev->slave_detected = i2c_detect_slave_mode(&pdev->dev);
+
+ if (dev->slave_detected)
+ rc = at91_twi_probe_slave(pdev, phy_addr, dev);
+ else
+ rc = at91_twi_probe_master(pdev, phy_addr, dev);
if (rc)
return rc;

diff --git a/drivers/i2c/busses/i2c-at91-slave.c b/drivers/i2c/busses/i2c-at91-slave.c
new file mode 100644
index 000000000000..4b4808e0c8f7
--- /dev/null
+++ b/drivers/i2c/busses/i2c-at91-slave.c
@@ -0,0 +1,147 @@
+/*
+ * i2c slave support for Atmel's AT91 Two-Wire Interface (TWI)
+ *
+ * Copyright (C) 2017 Juergen Fitschen <me@jue.yt>
+ *
+ * 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.
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/pm_runtime.h>
+
+#include "i2c-at91.h"
+
+static irqreturn_t atmel_twi_interrupt_slave(int irq, void *dev_id)
+{
+ struct at91_twi_dev *dev = dev_id;
+ const unsigned status = at91_twi_read(dev, AT91_TWI_SR);
+ const unsigned irqstatus = status & at91_twi_read(dev, AT91_TWI_IMR);
+ u8 value;
+
+ if (!irqstatus)
+ return IRQ_NONE;
+
+ /* slave address has been detected on I2C bus */
+ if (irqstatus & AT91_TWI_SVACC) {
+ if (status & AT91_TWI_SVREAD) {
+ i2c_slave_event(dev->slave,
+ I2C_SLAVE_READ_REQUESTED, &value);
+ writeb_relaxed(value, dev->base + AT91_TWI_THR);
+ at91_twi_write(dev, AT91_TWI_IER,
+ AT91_TWI_TXRDY | AT91_TWI_EOSACC);
+ } else {
+ i2c_slave_event(dev->slave,
+ I2C_SLAVE_WRITE_REQUESTED, &value);
+ at91_twi_write(dev, AT91_TWI_IER,
+ AT91_TWI_RXRDY | AT91_TWI_EOSACC);
+ }
+ at91_twi_write(dev, AT91_TWI_IDR, AT91_TWI_SVACC);
+ }
+
+ /* byte transmitted to remote master */
+ if (irqstatus & AT91_TWI_TXRDY) {
+ i2c_slave_event(dev->slave, I2C_SLAVE_READ_PROCESSED, &value);
+ writeb_relaxed(value, dev->base + AT91_TWI_THR);
+ }
+
+ /* byte received from remote master */
+ if (irqstatus & AT91_TWI_RXRDY) {
+ value = readb_relaxed(dev->base + AT91_TWI_RHR);
+ i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED, &value);
+ }
+
+ /* master sent stop */
+ if (irqstatus & AT91_TWI_EOSACC) {
+ at91_twi_write(dev, AT91_TWI_IDR,
+ AT91_TWI_TXRDY | AT91_TWI_RXRDY | AT91_TWI_EOSACC);
+ at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_SVACC);
+ i2c_slave_event(dev->slave, I2C_SLAVE_STOP, &value);
+ }
+
+ return IRQ_HANDLED;
+}
+
+static int at91_reg_slave(struct i2c_client *slave)
+{
+ struct at91_twi_dev *dev = i2c_get_adapdata(slave->adapter);
+
+ if (dev->slave)
+ return -EBUSY;
+
+ if (slave->flags & I2C_CLIENT_TEN)
+ return -EAFNOSUPPORT;
+
+ /* Make sure twi_clk doesn't get turned off! */
+ pm_runtime_get_sync(dev->dev);
+
+ dev->slave = slave;
+ dev->smr = AT91_TWI_SMR_SADR(slave->addr);
+
+ at91_init_twi_bus(dev);
+ at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_SVACC);
+
+ dev_info(dev->dev, "entered slave mode (ADR=%d)\n", slave->addr);
+
+ return 0;
+}
+
+static int at91_unreg_slave(struct i2c_client *slave)
+{
+ struct at91_twi_dev *dev = i2c_get_adapdata(slave->adapter);
+
+ WARN_ON(!dev->slave);
+
+ dev_info(dev->dev, "leaving slave mode\n");
+
+ dev->slave = NULL;
+ dev->smr = 0;
+
+ at91_init_twi_bus(dev);
+
+ pm_runtime_put(dev->dev);
+
+ return 0;
+}
+
+static u32 at91_twi_func(struct i2c_adapter *adapter)
+{
+ return I2C_FUNC_SLAVE | I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
+ | I2C_FUNC_SMBUS_READ_BLOCK_DATA;
+}
+
+static const struct i2c_algorithm at91_twi_algorithm_slave = {
+ .reg_slave = at91_reg_slave,
+ .unreg_slave = at91_unreg_slave,
+ .functionality = at91_twi_func,
+};
+
+int at91_twi_probe_slave(struct platform_device *pdev,
+ u32 phy_addr, struct at91_twi_dev *dev)
+{
+ int rc;
+
+ rc = devm_request_irq(&pdev->dev, dev->irq, atmel_twi_interrupt_slave,
+ 0, dev_name(dev->dev), dev);
+ if (rc) {
+ dev_err(dev->dev, "Cannot get irq %d: %d\n", dev->irq, rc);
+ return rc;
+ }
+
+ dev->adapter.algo = &at91_twi_algorithm_slave;
+
+ return 0;
+}
+
+void at91_init_twi_bus_slave(struct at91_twi_dev *dev)
+{
+ at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_MSDIS);
+ if (dev->slave_detected && dev->smr) {
+ at91_twi_write(dev, AT91_TWI_SMR, dev->smr);
+ at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SVEN);
+ }
+}
diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
index 555b1674ddbe..14cc71433366 100644
--- a/drivers/i2c/busses/i2c-at91.h
+++ b/drivers/i2c/busses/i2c-at91.h
@@ -53,6 +53,10 @@
#define AT91_TWI_IADRSZ_1 0x0100 /* Internal Device Address Size */
#define AT91_TWI_MREAD BIT(12) /* Master Read Direction */

+#define AT91_TWI_SMR 0x0008 /* Slave Mode Register */
+#define AT91_TWI_SMR_SADR_MAX 0x007f
+#define AT91_TWI_SMR_SADR(x) (((x) & AT91_TWI_SMR_SADR_MAX) << 16)
+
#define AT91_TWI_IADR 0x000c /* Internal Address Register */

#define AT91_TWI_CWGR 0x0010 /* Clock Waveform Generator Reg */
@@ -63,13 +67,17 @@
#define AT91_TWI_TXCOMP BIT(0) /* Transmission Complete */
#define AT91_TWI_RXRDY BIT(1) /* Receive Holding Register Ready */
#define AT91_TWI_TXRDY BIT(2) /* Transmit Holding Register Ready */
+#define AT91_TWI_SVREAD BIT(3) /* Slave Read */
+#define AT91_TWI_SVACC BIT(4) /* Slave Access */
#define AT91_TWI_OVRE BIT(6) /* Overrun Error */
#define AT91_TWI_UNRE BIT(7) /* Underrun Error */
#define AT91_TWI_NACK BIT(8) /* Not Acknowledged */
+#define AT91_TWI_EOSACC BIT(11) /* End Of Slave Access */
#define AT91_TWI_LOCK BIT(23) /* TWI Lock due to Frame Errors */

#define AT91_TWI_INT_MASK \
- (AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK)
+ (AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK \
+ | AT91_TWI_SVACC | AT91_TWI_EOSACC)

#define AT91_TWI_IER 0x0024 /* Interrupt Enable Register */
#define AT91_TWI_IDR 0x0028 /* Interrupt Disable Register */
@@ -137,6 +145,11 @@ struct at91_twi_dev {
bool recv_len_abort;
u32 fifo_size;
struct at91_twi_dma dma;
+ bool slave_detected;
+#if IS_ENABLED(CONFIG_I2C_AT91_SLAVE_EXPERIMENTAL)
+ unsigned smr;
+ struct i2c_client *slave;
+#endif
};

unsigned at91_twi_read(struct at91_twi_dev *dev, unsigned reg);
@@ -149,3 +162,18 @@ void at91_init_twi_bus(struct at91_twi_dev *dev);
void at91_init_twi_bus_master(struct at91_twi_dev *dev);
int at91_twi_probe_master(struct platform_device *pdev, u32 phy_addr,
struct at91_twi_dev *dev);
+
+#if IS_ENABLED(CONFIG_I2C_AT91_SLAVE_EXPERIMENTAL)
+void at91_init_twi_bus_slave(struct at91_twi_dev *dev);
+int at91_twi_probe_slave(struct platform_device *pdev, u32 phy_addr,
+ struct at91_twi_dev *dev);
+
+#else
+static inline void at91_init_twi_bus_slave(struct at91_twi_dev *dev) {}
+static inline int at91_twi_probe_slave(struct platform_device *pdev,
+ u32 phy_addr, struct at91_twi_dev *dev)
+{
+ return -EINVAL;
+}
+
+#endif
--
2.20.1
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