[PATCH 6/7] pwm: st: Add new driver for ST's PWM IP

Lee Jones
2014-06-18T14:53:52Z

This driver supports all current STi platforms' PWM IPs.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
drivers/pwm/Kconfig | 9 ++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-st.c | 378 +++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 388 insertions(+)
create mode 100644 drivers/pwm/pwm-st.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 4ad7b89..98a7bbc 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -292,4 +292,13 @@ config PWM_VT8500
To compile this driver as a module, choose M here: the module
will be called pwm-vt8500.

+config PWM_ST
+ tristate "STiH4xx PWM support"
+ depends on ARCH_STI
+ help
+ Generic PWM framework driver for STiH4xx SoCs.
+
+ To compile this driver as a module, choose M here: the module
+ will be called pwm-st.
+
endif
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 5c86a19..2c846a6 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_PWM_PXA) += pwm-pxa.o
obj-$(CONFIG_PWM_RENESAS_TPU) += pwm-renesas-tpu.o
obj-$(CONFIG_PWM_SAMSUNG) += pwm-samsung.o
obj-$(CONFIG_PWM_SPEAR) += pwm-spear.o
+obj-$(CONFIG_PWM_ST) += pwm-st.o
obj-$(CONFIG_PWM_TEGRA) += pwm-tegra.o
obj-$(CONFIG_PWM_TIECAP) += pwm-tiecap.o
obj-$(CONFIG_PWM_TIEHRPWM) += pwm-tiehrpwm.o
diff --git a/drivers/pwm/pwm-st.c b/drivers/pwm/pwm-st.c
new file mode 100644
index 0000000..4dea616
--- /dev/null
+++ b/drivers/pwm/pwm-st.c
@@ -0,0 +1,378 @@
+/*
+ * PWM device driver for ST SoCs.
+ * Author: Ajit Pal Singh <ajitpal.singh@st.com>
+ *
+ * Copyright (C) 2003-2014 STMicroelectronics (R&D) Limited
+ *
+ * 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/bsearch.h>
+#include <linux/clk.h>
+#include <linux/math64.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/mfd/syscon.h>
+#include <linux/time.h>
+
+#define ST_PWMVAL(x) (4 * (x)) /* Value used to define duty cycle */
+#define ST_PWMCR 0x50 /* Control/Config reg */
+#define ST_INTEN 0x54 /* Interrupt Enable/Disable reg */
+#define ST_CNT 0x60 /* PWMCounter */
+
+#define MAX_PWM_CNT_DEFAULT 255
+#define MAX_PRESCALE_DEFAULT 0xff
+#define NUM_CHAN_DEFAULT 1
+
+/* Regfield IDs */
+enum {
+ PWMCLK_PRESCALE = 0,
+ PWM_EN,
+ PWM_INT_EN,
+ /* keep last */
+ MAX_REGFIELDS
+};
+
+struct st_pwm_chip {
+ struct device *dev;
+ struct clk *clk;
+ unsigned long clk_rate;
+ struct regmap *regmap;
+ struct st_pwm_compat_data *cdata;
+ struct regmap_field *prescale;
+ struct regmap_field *pwm_en;
+ struct regmap_field *pwm_int_en;
+ unsigned long *pwm_periods;
+ struct pwm_chip chip;
+ void __iomem *mmio_base;
+};
+
+struct st_pwm_compat_data {
+ const struct reg_field *reg_fields;
+ int num_chan;
+ int max_pwm_cnt;
+ int max_prescale;
+};
+
+static const struct reg_field st_pwm_regfields[MAX_REGFIELDS] = {
+ [PWMCLK_PRESCALE] = REG_FIELD(ST_PWMCR, 0, 3),
+ [PWM_EN] = REG_FIELD(ST_PWMCR, 9, 9),
+ [PWM_INT_EN] = REG_FIELD(ST_INTEN, 0, 0),
+};
+
+static inline struct st_pwm_chip *to_st_pwmchip(struct pwm_chip *chip)
+{
+ return container_of(chip, struct st_pwm_chip, chip);
+}
+
+/*
+ * Calculate the period values supported by the PWM for the
+ * current clock rate.
+ */
+static void st_pwm_calc_periods(struct st_pwm_chip *pc)
+{
+ struct st_pwm_compat_data *cdata = pc->cdata;
+ struct device *dev = pc->dev;
+ unsigned long val;
+ int i;
+
+ /*
+ * period_ns = (10^9 * (prescaler + 1) * (MAX_PWM_COUNT + 1)) / CLK_RATE
+ */
+ val = NSEC_PER_SEC / pc->clk_rate;
+ val *= cdata->max_pwm_cnt + 1;
+
+ dev_dbg(dev, "possible periods for clkrate[HZ]:%lu\n", pc->clk_rate);
+
+ for (i = 0; i <= cdata->max_prescale; i++) {
+ pc->pwm_periods[i] = val * (i + 1);
+ dev_dbg(dev, "prescale:%d, period[ns]:%lu\n",
+ i, pc->pwm_periods[i]);
+ }
+}
+
+static int st_pwm_cmp_periods(const void *key, const void *elt)
+{
+ unsigned long i = *(unsigned long *)key;
+ unsigned long j = *(unsigned long *)elt;
+
+ if (i < j)
+ return -1;
+ else
+ return i == j ? 0 : 1;
+}
+
+/*
+ * For STiH4xx PWM IP, the pwm period is fixed to 256 local clock cycles.
+ * The only way to change the period (apart from changing the pwm input clock)
+ * is to change the pwm clock prescaler.
+ * The prescaler is of 4 bits, so only 16 prescaler values and hence only
+ * 16 possible period values are supported (for a particular clock rate).
+ * The requested period will be applied only if it matches one of these
+ * 16 values.
+ */
+static int st_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+ int duty_ns, int period_ns)
+{
+ struct st_pwm_chip *pc = to_st_pwmchip(chip);
+ struct device *dev = pc->dev;
+ struct st_pwm_compat_data *cdata = pc->cdata;
+ unsigned int prescale, pwmvalx;
+ unsigned long *found;
+ int ret;
+
+ /*
+ * Search for matching period value. The corresponding index is our
+ * prescale value
+ */
+ found = bsearch(&period_ns, &pc->pwm_periods[0],
+ cdata->max_prescale + 1, sizeof(unsigned long),
+ st_pwm_cmp_periods);
+ if (!found) {
+ dev_err(dev, "failed to find matching period\n");
+ return -EINVAL;
+ }
+
+ prescale = found - &pc->pwm_periods[0];
+
+ /*
+ * When PWMVal == 0, PWM pulse = 1 local clock cycle.
+ * When PWMVal == max_pwm_count,
+ * PWM pulse = (max_pwm_count + 1) local cycles,
+ * that is continuous pulse: signal never goes low.
+ */
+ pwmvalx = cdata->max_pwm_cnt * duty_ns / period_ns;
+
+ dev_dbg(dev, "prescale:%u, period:%i, duty:%i, pwmvalx:%u\n",
+ prescale, period_ns, duty_ns, pwmvalx);
+
+ /* Enable clock before writing to PWM registers */
+ ret = clk_enable(pc->clk);
+ if (ret)
+ return ret;
+
+ ret = regmap_field_write(pc->prescale, prescale);
+ if (ret)
+ goto clk_dis;
+
+ ret = regmap_write(pc->regmap, ST_PWMVAL(pwm->hwpwm), pwmvalx);
+ if (ret)
+ goto clk_dis;
+
+ ret = regmap_field_write(pc->pwm_int_en, 0);
+
+clk_dis:
+ clk_disable(pc->clk);
+ return ret;
+}
+
+static int st_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+ struct st_pwm_chip *pc = to_st_pwmchip(chip);
+ struct device *dev = pc->dev;
+ int ret;
+
+ ret = clk_enable(pc->clk);
+ if (ret)
+ return ret;
+
+ ret = regmap_field_write(pc->pwm_en, 1);
+ if (ret)
+ dev_err(dev, "%s,pwm_en write failed\n", __func__);
+
+ return ret;
+}
+
+static void st_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+ struct st_pwm_chip *pc = to_st_pwmchip(chip);
+ struct device *dev = pc->dev;
+ unsigned int val;
+
+ regmap_field_write(pc->pwm_en, 0);
+
+ regmap_read(pc->regmap, ST_CNT, &val);
+
+ dev_dbg(dev, "pwm counter :%u\n", val);
+
+ clk_disable(pc->clk);
+}
+
+static const struct pwm_ops st_pwm_ops = {
+ .config = st_pwm_config,
+ .enable = st_pwm_enable,
+ .disable = st_pwm_disable,
+ .owner = THIS_MODULE,
+};
+
+static int st_pwm_probe_dt(struct st_pwm_chip *pc)
+{
+ struct device *dev = pc->dev;
+ const struct reg_field *reg_fields;
+ struct device_node *np = dev->of_node;
+ struct st_pwm_compat_data *cdata = pc->cdata;
+ u32 num_chan;
+
+ of_property_read_u32(np, "st,pwm-num-chan", &num_chan);
+ if (num_chan)
+ cdata->num_chan = num_chan;
+
+ reg_fields = cdata->reg_fields;
+
+ pc->prescale = devm_regmap_field_alloc(dev, pc->regmap,
+ reg_fields[PWMCLK_PRESCALE]);
+ pc->pwm_en = devm_regmap_field_alloc(dev, pc->regmap,
+ reg_fields[PWM_EN]);
+ pc->pwm_int_en = devm_regmap_field_alloc(dev, pc->regmap,
+ reg_fields[PWM_INT_EN]);
+
+ if (IS_ERR(pc->prescale) ||
+ IS_ERR(pc->pwm_en) ||
+ IS_ERR(pc->pwm_int_en)) {
+ dev_err(dev, "unable to allocate reg_field(s)\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static struct regmap_config st_pwm_regmap_config = {
+ .reg_bits = 32,
+ .val_bits = 32,
+ .reg_stride = 4,
+};
+
+static int st_pwm_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *np = dev->of_node;
+ struct st_pwm_compat_data *cdata;
+ struct st_pwm_chip *pc;
+ struct resource *res;
+ int ret;
+
+ if (!np) {
+ dev_err(dev, "failed to find device node\n");
+ return -EINVAL;
+ }
+
+ pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
+ if (!pc)
+ return -ENOMEM;
+
+ cdata = devm_kzalloc(dev, sizeof(*cdata), GFP_KERNEL);
+ if (!cdata)
+ return -ENOMEM;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+
+ pc->mmio_base = devm_ioremap_resource(dev, res);
+ if (IS_ERR(pc->mmio_base)) {
+ dev_err(dev, "failed to find and map memory resources\n");
+ return PTR_ERR(pc->mmio_base);
+ }
+
+ pc->regmap = devm_regmap_init_mmio(dev, pc->mmio_base,
+ &st_pwm_regmap_config);
+ if (IS_ERR(pc->regmap))
+ return PTR_ERR(pc->regmap);
+
+ /*
+ * Setup PWM data with default values: some values could be replaced
+ * with specific ones provided from device tree
+ */
+ cdata->reg_fields = &st_pwm_regfields[0];
+ cdata->max_pwm_cnt = MAX_PWM_CNT_DEFAULT;
+ cdata->max_prescale = MAX_PRESCALE_DEFAULT;
+ cdata->num_chan = NUM_CHAN_DEFAULT;
+
+ pc->cdata = cdata;
+ pc->dev = dev;
+
+ ret = st_pwm_probe_dt(pc);
+ if (ret)
+ return ret;
+
+ pc->pwm_periods = devm_kzalloc(dev,
+ sizeof(unsigned long) * (pc->cdata->max_prescale + 1),
+ GFP_KERNEL);
+ if (!pc->pwm_periods)
+ return -ENOMEM;
+
+ pc->clk = of_clk_get_by_name(np, "pwm");
+ if (IS_ERR(pc->clk)) {
+ dev_err(dev, "failed to get pwm clock\n");
+ return PTR_ERR(pc->clk);
+ }
+
+ pc->clk_rate = clk_get_rate(pc->clk);
+ if (!pc->clk_rate) {
+ dev_err(dev, "failed to get clk rate\n");
+ return -EINVAL;
+ }
+
+ ret = clk_prepare(pc->clk);
+ if (ret) {
+ dev_err(dev, "failed to prepare clk\n");
+ return ret;
+ }
+
+ st_pwm_calc_periods(pc);
+
+ pc->chip.dev = dev;
+ pc->chip.ops = &st_pwm_ops;
+ pc->chip.base = -1;
+ pc->chip.npwm = pc->cdata->num_chan;
+ pc->chip.can_sleep = true;
+
+ ret = pwmchip_add(&pc->chip);
+ if (ret < 0) {
+ clk_unprepare(pc->clk);
+ return ret;
+ }
+
+ platform_set_drvdata(pdev, pc);
+
+ return 0;
+}
+
+static int st_pwm_remove(struct platform_device *pdev)
+{
+ struct st_pwm_chip *pc = platform_get_drvdata(pdev);
+ int i;
+
+ for (i = 0; i < pc->cdata->num_chan; i++)
+ pwm_disable(&pc->chip.pwms[i]);
+
+ clk_unprepare(pc->clk);
+
+ return pwmchip_remove(&pc->chip);
+}
+
+static struct of_device_id st_pwm_of_match[] = {
+ { .compatible = "st,sti-pwm", },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, st_pwm_of_match);
+
+static struct platform_driver st_pwm_driver = {
+ .driver = {
+ .name = "st-pwm",
+ .owner = THIS_MODULE,
+ .of_match_table = st_pwm_of_match,
+ },
+ .probe = st_pwm_probe,
+ .remove = st_pwm_remove,
+};
+module_platform_driver(st_pwm_driver);
+
+MODULE_AUTHOR("STMicroelectronics (R&D) Limited <ajitpal.singh@st.com>");
+MODULE_DESCRIPTION("STMicroelectronics ST PWM driver");
+MODULE_LICENSE("GPL v2");
--
1.8.3.2