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Subject[PATCH v7 2/2] rtc: support for the Amlogic Meson RTC
Date
Add support for the RTC block on the 32-bit Amlogic Meson6, Meson8,
Meson8b and Meson8m2 SoCs.

The RTC is split in to two parts, which are both managed by this driver:
- the AHB front end
- and a simple serial connection to the actual registers

The RTC_COUNTER register which holds the time is 32-bits wide.

There are four 32-bit wide (in total: 16 bytes) "regmem" registers which
are exposed using nvmem. On Amlogic's 3.10 kernel this is used to store
data which needs to survive a suspend / resume cycle.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
[resurrected Ben's patches after 2 years]
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
---
drivers/rtc/Kconfig | 11 ++
drivers/rtc/Makefile | 1 +
drivers/rtc/rtc-meson.c | 410 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 422 insertions(+)
create mode 100644 drivers/rtc/rtc-meson.c

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 225b0b8516f3..7f10e5e5ce05 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1285,6 +1285,17 @@ config RTC_DRV_IMXDI
This driver can also be built as a module, if so, the module
will be called "rtc-imxdi".

+config RTC_DRV_MESON
+ tristate "Amlogic Meson RTC"
+ depends on (ARM && ARCH_MESON) || COMPILE_TEST
+ select REGMAP_MMIO
+ help
+ Support for the RTC block on the Amlogic Meson6, Meson8, Meson8b
+ and Meson8m2 SoCs.
+
+ This driver can also be built as a module, if so, the module
+ will be called "rtc-meson".
+
config RTC_DRV_OMAP
tristate "TI OMAP Real Time Clock"
depends on ARCH_OMAP || ARCH_DAVINCI || COMPILE_TEST
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index df022d820bee..cf02a5c7a38b 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -100,6 +100,7 @@ obj-$(CONFIG_RTC_DRV_MAX8997) += rtc-max8997.o
obj-$(CONFIG_RTC_DRV_MAX8998) += rtc-max8998.o
obj-$(CONFIG_RTC_DRV_MC13XXX) += rtc-mc13xxx.o
obj-$(CONFIG_RTC_DRV_MCP795) += rtc-mcp795.o
+obj-$(CONFIG_RTC_DRV_MESON) += rtc-meson.o
obj-$(CONFIG_RTC_DRV_MOXART) += rtc-moxart.o
obj-$(CONFIG_RTC_DRV_MPC5121) += rtc-mpc5121.o
obj-$(CONFIG_RTC_DRV_MSM6242) += rtc-msm6242.o
diff --git a/drivers/rtc/rtc-meson.c b/drivers/rtc/rtc-meson.c
new file mode 100644
index 000000000000..6fc4b09e7ebd
--- /dev/null
+++ b/drivers/rtc/rtc-meson.c
@@ -0,0 +1,410 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RTC driver for the interal RTC block in the Amlogic Meson6, Meson8,
+ * Meson8b and Meson8m2 SoCs.
+ *
+ * The RTC is split in to two parts, the AHB front end and a simple serial
+ * connection to the actual registers. This driver manages both parts.
+ *
+ * Copyright (c) 2018 Martin Blumenstingl <martin.blumenstingl@googlemail.com>
+ * Copyright (c) 2015 Ben Dooks <ben.dooks@codethink.co.uk> for Codethink Ltd
+ * Based on origin by Carlo Caione <carlo@endlessm.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/reset.h>
+#include <linux/rtc.h>
+
+/* registers accessed from cpu bus */
+#define RTC_ADDR0 0x00
+ #define RTC_ADDR0_LINE_SCLK BIT(0)
+ #define RTC_ADDR0_LINE_SEN BIT(1)
+ #define RTC_ADDR0_LINE_SDI BIT(2)
+ #define RTC_ADDR0_START_SER BIT(17)
+ #define RTC_ADDR0_WAIT_SER BIT(22)
+ #define RTC_ADDR0_DATA GENMASK(31, 24)
+
+#define RTC_ADDR1 0x04
+ #define RTC_ADDR1_SDO BIT(0)
+ #define RTC_ADDR1_S_READY BIT(1)
+
+#define RTC_ADDR2 0x08
+#define RTC_ADDR3 0x0c
+
+#define RTC_REG4 0x10
+ #define RTC_REG4_STATIC_VALUE GENMASK(7, 0)
+
+/* rtc registers accessed via rtc-serial interface */
+#define RTC_COUNTER (0)
+#define RTC_SEC_ADJ (2)
+#define RTC_REGMEM_0 (4)
+#define RTC_REGMEM_1 (5)
+#define RTC_REGMEM_2 (6)
+#define RTC_REGMEM_3 (7)
+
+#define RTC_ADDR_BITS (3) /* number of address bits to send */
+#define RTC_DATA_BITS (32) /* number of data bits to tx/rx */
+
+#define MESON_STATIC_BIAS_CUR (0x5 << 1)
+#define MESON_STATIC_VOLTAGE (0x3 << 11)
+#define MESON_STATIC_DEFAULT (MESON_STATIC_BIAS_CUR | MESON_STATIC_VOLTAGE)
+
+struct meson_rtc {
+ struct rtc_device *rtc; /* rtc device we created */
+ struct device *dev; /* device we bound from */
+ struct reset_control *reset; /* reset source */
+ struct regulator *vdd; /* voltage input */
+ struct regmap *peripheral; /* peripheral registers */
+ struct regmap *serial; /* serial registers */
+};
+
+static const struct regmap_config meson_rtc_peripheral_regmap_config = {
+ .name = "peripheral-registers",
+ .reg_bits = 8,
+ .val_bits = 32,
+ .reg_stride = 4,
+ .max_register = RTC_REG4,
+ .fast_io = true,
+};
+
+/* RTC front-end serialiser controls */
+
+static void meson_rtc_sclk_pulse(struct meson_rtc *rtc)
+{
+ udelay(5);
+ regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SCLK, 0);
+ udelay(5);
+ regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SCLK,
+ RTC_ADDR0_LINE_SCLK);
+}
+
+static void meson_rtc_send_bit(struct meson_rtc *rtc, unsigned int bit)
+{
+ regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI,
+ bit ? RTC_ADDR0_LINE_SDI : 0);
+ meson_rtc_sclk_pulse(rtc);
+}
+
+static void meson_rtc_send_bits(struct meson_rtc *rtc, u32 data,
+ unsigned int nr)
+{
+ u32 bit = 1 << (nr - 1);
+
+ while (bit) {
+ meson_rtc_send_bit(rtc, data & bit);
+ bit >>= 1;
+ }
+}
+
+static void meson_rtc_set_dir(struct meson_rtc *rtc, u32 mode)
+{
+ regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN, 0);
+ regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI, 0);
+ meson_rtc_send_bit(rtc, mode);
+ regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI, 0);
+}
+
+static u32 meson_rtc_get_data(struct meson_rtc *rtc)
+{
+ u32 tmp, val = 0;
+ int bit;
+
+ for (bit = 0; bit < RTC_DATA_BITS; bit++) {
+ meson_rtc_sclk_pulse(rtc);
+ val <<= 1;
+
+ regmap_read(rtc->peripheral, RTC_ADDR1, &tmp);
+ val |= tmp & RTC_ADDR1_SDO;
+ }
+
+ return val;
+}
+
+static int meson_rtc_get_bus(struct meson_rtc *rtc)
+{
+ int ret, retries = 3;
+ u32 val;
+
+ /* prepare bus for transfers, set all lines low */
+ val = RTC_ADDR0_LINE_SDI | RTC_ADDR0_LINE_SEN | RTC_ADDR0_LINE_SCLK;
+ regmap_update_bits(rtc->peripheral, RTC_ADDR0, val, 0);
+
+ for (retries = 0; retries < 3; retries++) {
+ /* wait for the bus to be ready */
+ if (!regmap_read_poll_timeout(rtc->peripheral, RTC_ADDR1, val,
+ val & RTC_ADDR1_S_READY, 10,
+ 10000))
+ return 0;
+
+ dev_warn(rtc->dev, "failed to get bus, resetting RTC\n");
+
+ ret = reset_control_reset(rtc->reset);
+ if (ret)
+ return ret;
+ }
+
+ dev_err(rtc->dev, "bus is not ready\n");
+ return -ETIMEDOUT;
+}
+
+static int meson_rtc_serial_bus_reg_read(void *context, unsigned int reg,
+ unsigned int *data)
+{
+ struct meson_rtc *rtc = context;
+ int ret;
+
+ ret = meson_rtc_get_bus(rtc);
+ if (ret)
+ return ret;
+
+ regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN,
+ RTC_ADDR0_LINE_SEN);
+ meson_rtc_send_bits(rtc, reg, RTC_ADDR_BITS);
+ meson_rtc_set_dir(rtc, 0);
+ *data = meson_rtc_get_data(rtc);
+
+ return 0;
+}
+
+static int meson_rtc_serial_bus_reg_write(void *context, unsigned int reg,
+ unsigned int data)
+{
+ struct meson_rtc *rtc = context;
+ int ret;
+
+ ret = meson_rtc_get_bus(rtc);
+ if (ret)
+ return ret;
+
+ regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN,
+ RTC_ADDR0_LINE_SEN);
+ meson_rtc_send_bits(rtc, data, RTC_DATA_BITS);
+ meson_rtc_send_bits(rtc, reg, RTC_ADDR_BITS);
+ meson_rtc_set_dir(rtc, 1);
+
+ return 0;
+}
+
+static const struct regmap_bus meson_rtc_serial_bus = {
+ .reg_read = meson_rtc_serial_bus_reg_read,
+ .reg_write = meson_rtc_serial_bus_reg_write,
+};
+
+static const struct regmap_config meson_rtc_serial_regmap_config = {
+ .name = "serial-registers",
+ .reg_bits = 4,
+ .reg_stride = 1,
+ .val_bits = 32,
+ .max_register = RTC_REGMEM_3,
+ .fast_io = false,
+};
+
+static int meson_rtc_write_static(struct meson_rtc *rtc, u32 data)
+{
+ u32 tmp;
+
+ regmap_write(rtc->peripheral, RTC_REG4,
+ FIELD_PREP(RTC_REG4_STATIC_VALUE, (data >> 8)));
+
+ /* write the static value and start the auto serializer */
+ tmp = FIELD_PREP(RTC_ADDR0_DATA, (data & 0xff)) | RTC_ADDR0_START_SER;
+ regmap_update_bits(rtc->peripheral, RTC_ADDR0,
+ RTC_ADDR0_DATA | RTC_ADDR0_START_SER, tmp);
+
+ /* wait for the auto serializer to complete */
+ return regmap_read_poll_timeout(rtc->peripheral, RTC_REG4, tmp,
+ !(tmp & RTC_ADDR0_WAIT_SER), 10,
+ 10000);
+}
+
+/* RTC interface layer functions */
+
+static int meson_rtc_gettime(struct device *dev, struct rtc_time *tm)
+{
+ struct meson_rtc *rtc = dev_get_drvdata(dev);
+ u32 time;
+ int ret;
+
+ ret = regmap_read(rtc->serial, RTC_COUNTER, &time);
+ if (!ret)
+ rtc_time64_to_tm(time, tm);
+
+ return ret;
+}
+
+static int meson_rtc_settime(struct device *dev, struct rtc_time *tm)
+{
+ struct meson_rtc *rtc = dev_get_drvdata(dev);
+
+ return regmap_write(rtc->serial, RTC_COUNTER, rtc_tm_to_time64(tm));
+}
+
+static const struct rtc_class_ops meson_rtc_ops = {
+ .read_time = meson_rtc_gettime,
+ .set_time = meson_rtc_settime,
+};
+
+/* NVMEM interface layer functions */
+
+static int meson_rtc_regmem_read(void *context, unsigned int offset,
+ void *buf, size_t bytes)
+{
+ struct meson_rtc *rtc = context;
+ unsigned int read_offset, read_size;
+
+ read_offset = RTC_REGMEM_0 + (offset / 4);
+ read_size = bytes / 4;
+
+ return regmap_bulk_read(rtc->serial, read_offset, buf, read_size);
+}
+
+static int meson_rtc_regmem_write(void *context, unsigned int offset,
+ void *buf, size_t bytes)
+{
+ struct meson_rtc *rtc = context;
+ unsigned int write_offset, write_size;
+
+ write_offset = RTC_REGMEM_0 + (offset / 4);
+ write_size = bytes / 4;
+
+ return regmap_bulk_write(rtc->serial, write_offset, buf, write_size);
+}
+
+static int meson_rtc_probe(struct platform_device *pdev)
+{
+ struct nvmem_config meson_rtc_nvmem_config = {
+ .name = "meson-rtc-regmem",
+ .type = NVMEM_TYPE_BATTERY_BACKED,
+ .word_size = 4,
+ .stride = 4,
+ .size = 4 * 4,
+ .reg_read = meson_rtc_regmem_read,
+ .reg_write = meson_rtc_regmem_write,
+ };
+ struct device *dev = &pdev->dev;
+ struct meson_rtc *rtc;
+ struct resource *res;
+ void __iomem *base;
+ int ret;
+ u32 tm;
+
+ rtc = devm_kzalloc(dev, sizeof(struct meson_rtc), GFP_KERNEL);
+ if (!rtc)
+ return -ENOMEM;
+
+ rtc->rtc = devm_rtc_allocate_device(dev);
+ if (IS_ERR(rtc->rtc))
+ return PTR_ERR(rtc->rtc);
+
+ platform_set_drvdata(pdev, rtc);
+
+ rtc->dev = dev;
+
+ rtc->rtc->ops = &meson_rtc_ops;
+ rtc->rtc->range_max = U32_MAX;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ base = devm_ioremap_resource(dev, res);
+ if (IS_ERR(base))
+ return PTR_ERR(base);
+
+ rtc->peripheral = devm_regmap_init_mmio(dev, base,
+ &meson_rtc_peripheral_regmap_config);
+ if (IS_ERR(rtc->peripheral)) {
+ dev_err(dev, "failed to create peripheral regmap\n");
+ return PTR_ERR(rtc->peripheral);
+ }
+
+ rtc->reset = devm_reset_control_get(dev, NULL);
+ if (IS_ERR(rtc->reset)) {
+ dev_err(dev, "missing reset line\n");
+ return PTR_ERR(rtc->reset);
+ }
+
+ rtc->vdd = devm_regulator_get(dev, "vdd");
+ if (IS_ERR(rtc->vdd)) {
+ dev_err(dev, "failed to get the vdd-supply\n");
+ return PTR_ERR(rtc->vdd);
+ }
+
+ ret = regulator_enable(rtc->vdd);
+ if (ret) {
+ dev_err(dev, "failed to enable vdd-supply\n");
+ return ret;
+ }
+
+ ret = meson_rtc_write_static(rtc, MESON_STATIC_DEFAULT);
+ if (ret) {
+ dev_err(dev, "failed to set static values\n");
+ goto out_disable_vdd;
+ }
+
+ rtc->serial = devm_regmap_init(dev, &meson_rtc_serial_bus, rtc,
+ &meson_rtc_serial_regmap_config);
+ if (IS_ERR(rtc->serial)) {
+ dev_err(dev, "failed to create serial regmap\n");
+ ret = PTR_ERR(rtc->serial);
+ goto out_disable_vdd;
+ }
+
+ /*
+ * check if we can read RTC counter, if not then the RTC is probably
+ * not functional. If it isn't probably best to not bind.
+ */
+ ret = regmap_read(rtc->serial, RTC_COUNTER, &tm);
+ if (ret) {
+ dev_err(dev, "cannot read RTC counter, RTC not functional\n");
+ goto out_disable_vdd;
+ }
+
+ meson_rtc_nvmem_config.priv = rtc;
+ ret = rtc_nvmem_register(rtc->rtc, &meson_rtc_nvmem_config);
+ if (ret)
+ goto out_disable_vdd;
+
+ ret = rtc_register_device(rtc->rtc);
+ if (ret)
+ goto out_unregister_nvmem;
+
+ return 0;
+
+out_unregister_nvmem:
+ rtc_nvmem_unregister(rtc->rtc);
+
+out_disable_vdd:
+ regulator_disable(rtc->vdd);
+ return ret;
+}
+
+static const struct of_device_id meson_rtc_dt_match[] = {
+ { .compatible = "amlogic,meson6-rtc", },
+ { .compatible = "amlogic,meson8-rtc", },
+ { .compatible = "amlogic,meson8b-rtc", },
+ { .compatible = "amlogic,meson8m2-rtc", },
+ { },
+};
+MODULE_DEVICE_TABLE(of, meson_rtc_dt_match);
+
+static struct platform_driver meson_rtc_driver = {
+ .probe = meson_rtc_probe,
+ .driver = {
+ .name = "meson-rtc",
+ .of_match_table = of_match_ptr(meson_rtc_dt_match),
+ },
+};
+module_platform_driver(meson_rtc_driver);
+
+MODULE_DESCRIPTION("Amlogic Meson RTC Driver");
+MODULE_AUTHOR("Ben Dooks <ben.doosk@codethink.co.uk>");
+MODULE_AUTHOR("Martin Blumenstingl <martin.blumenstingl@googlemail.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:meson-rtc");
--
2.20.1
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