[PATCH v11 2/2] pwm: sifive: Add a driver for SiFive SoC PWM

Yash Shah
2019-03-25T10:13:34Z

Adds a PWM driver for PWM chip present in SiFive's HiFive Unleashed SoC.

Signed-off-by: Wesley W. Terpstra <wesley@sifive.com>
[Atish: Various fixes and code cleanup]
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Yash Shah <yash.shah@sifive.com>
---
drivers/pwm/Kconfig | 11 ++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-sifive.c | 338 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 350 insertions(+)
create mode 100644 drivers/pwm/pwm-sifive.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index a8f47df..4a61d1a 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -380,6 +380,17 @@ config PWM_SAMSUNG
To compile this driver as a module, choose M here: the module
will be called pwm-samsung.

+config PWM_SIFIVE
+ tristate "SiFive PWM support"
+ depends on OF
+ depends on COMMON_CLK
+ depends on RISCV || COMPILE_TEST
+ help
+ Generic PWM framework driver for SiFive SoCs.
+
+ To compile this driver as a module, choose M here: the module
+ will be called pwm-sifive.
+
config PWM_SPEAR
tristate "STMicroelectronics SPEAr PWM support"
depends on PLAT_SPEAR
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 9c676a0..30089ca 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -37,6 +37,7 @@ obj-$(CONFIG_PWM_RCAR) += pwm-rcar.o
obj-$(CONFIG_PWM_RENESAS_TPU) += pwm-renesas-tpu.o
obj-$(CONFIG_PWM_ROCKCHIP) += pwm-rockchip.o
obj-$(CONFIG_PWM_SAMSUNG) += pwm-samsung.o
+obj-$(CONFIG_PWM_SIFIVE) += pwm-sifive.o
obj-$(CONFIG_PWM_SPEAR) += pwm-spear.o
obj-$(CONFIG_PWM_STI) += pwm-sti.o
obj-$(CONFIG_PWM_STM32) += pwm-stm32.o
diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
new file mode 100644
index 0000000..1921e6ea
--- /dev/null
+++ b/drivers/pwm/pwm-sifive.c
@@ -0,0 +1,338 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017-2018 SiFive
+ * For SiFive's PWM IP block documentation please refer Chapter 14 of
+ * Reference Manual : https://static.dev.sifive.com/FU540-C000-v1.0.pdf
+ *
+ * Limitations:
+ * - When changing both duty cycle and period, we cannot prevent in
+ * software that the output might produce a period with mixed
+ * settings (new period length and old duty cycle).
+ * - The hardware cannot generate a 100% duty cycle.
+ * - The hardware generates only inverted output.
+ */
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/slab.h>
+#include <linux/bitfield.h>
+
+/* Register offsets */
+#define PWM_SIFIVE_PWMCFG 0x0
+#define PWM_SIFIVE_PWMCOUNT 0x8
+#define PWM_SIFIVE_PWMS 0x10
+#define PWM_SIFIVE_PWMCMP0 0x20
+
+/* PWMCFG fields */
+#define PWM_SIFIVE_PWMCFG_SCALE GENMASK(3, 0)
+#define PWM_SIFIVE_PWMCFG_STICKY BIT(8)
+#define PWM_SIFIVE_PWMCFG_ZERO_CMP BIT(9)
+#define PWM_SIFIVE_PWMCFG_DEGLITCH BIT(10)
+#define PWM_SIFIVE_PWMCFG_EN_ALWAYS BIT(12)
+#define PWM_SIFIVE_PWMCFG_EN_ONCE BIT(13)
+#define PWM_SIFIVE_PWMCFG_CENTER BIT(16)
+#define PWM_SIFIVE_PWMCFG_GANG BIT(24)
+#define PWM_SIFIVE_PWMCFG_IP BIT(28)
+
+/* PWM_SIFIVE_SIZE_PWMCMP is used to calculate offset for pwmcmpX registers */
+#define PWM_SIFIVE_SIZE_PWMCMP 4
+#define PWM_SIFIVE_CMPWIDTH 16
+#define PWM_SIFIVE_DEFAULT_PERIOD 10000000
+
+struct pwm_sifive_ddata {
+ struct pwm_chip chip;
+ struct mutex lock; /* lock to protect user_count */
+ struct notifier_block notifier;
+ struct clk *clk;
+ void __iomem *regs;
+ unsigned int real_period;
+ unsigned int approx_period;
+ int user_count;
+};
+
+static inline
+struct pwm_sifive_ddata *pwm_sifive_chip_to_ddata(struct pwm_chip *c)
+{
+ return container_of(c, struct pwm_sifive_ddata, chip);
+}
+
+static int pwm_sifive_request(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+ struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+
+ mutex_lock(&ddata->lock);
+ ddata->user_count++;
+ mutex_unlock(&ddata->lock);
+
+ return 0;
+}
+
+static void pwm_sifive_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+ struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+
+ mutex_lock(&ddata->lock);
+ ddata->user_count--;
+ mutex_unlock(&ddata->lock);
+}
+
+static void pwm_sifive_update_clock(struct pwm_sifive_ddata *ddata,
+ unsigned long rate)
+{
+ unsigned long long num;
+ unsigned long scale_pow;
+ int scale;
+ u32 val;
+ /*
+ * The PWM unit is used with pwmzerocmp=0, so the only way to modify the
+ * period length is using pwmscale which provides the number of bits the
+ * counter is shifted before being feed to the comparators. A period
+ * lasts (1 << (PWM_SIFIVE_CMPWIDTH + pwmscale)) clock ticks.
+ * (1 << (PWM_SIFIVE_CMPWIDTH + scale)) * 10^9/rate = period
+ */
+ scale_pow = div64_ul(ddata->approx_period * (u64)rate, NSEC_PER_SEC);
+ scale = clamp(ilog2(scale_pow) - PWM_SIFIVE_CMPWIDTH, 0, 0xf);
+
+ val = PWM_SIFIVE_PWMCFG_EN_ALWAYS |
+ FIELD_PREP(PWM_SIFIVE_PWMCFG_SCALE, scale);
+ writel(val, ddata->regs + PWM_SIFIVE_PWMCFG);
+
+ /* As scale <= 15 the shift operation cannot overflow. */
+ num = (unsigned long long)NSEC_PER_SEC << (PWM_SIFIVE_CMPWIDTH + scale);
+ ddata->real_period = div64_ul(num, rate);
+ dev_dbg(ddata->chip.dev,
+ "New real_period = %u ns\n", ddata->real_period);
+}
+
+static void pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+ u32 duty, val;
+
+ duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP0 +
+ pwm->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
+
+ state->enabled = duty > 0;
+
+ val = readl(ddata->regs + PWM_SIFIVE_PWMCFG);
+ if (!(val & PWM_SIFIVE_PWMCFG_EN_ALWAYS))
+ state->enabled = false;
+
+ state->period = ddata->real_period;
+ state->duty_cycle =
+ (u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
+ state->polarity = PWM_POLARITY_INVERSED;
+}
+
+static int pwm_sifive_enable(struct pwm_chip *chip, bool enable)
+{
+ struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+ int ret;
+
+ if (enable) {
+ ret = clk_enable(ddata->clk);
+ if (ret) {
+ dev_err(ddata->chip.dev, "Enable clk failed\n");
+ return ret;
+ }
+ }
+
+ if (!enable)
+ clk_disable(ddata->clk);
+
+ return 0;
+}
+
+static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+ struct pwm_state cur_state;
+ unsigned int duty_cycle;
+ unsigned long long num;
+ bool enabled;
+ int ret = 0;
+ u32 frac;
+
+ if (state->polarity != PWM_POLARITY_INVERSED)
+ return -EINVAL;
+
+ ret = clk_enable(ddata->clk);
+ if (ret) {
+ dev_err(ddata->chip.dev, "Enable clk failed\n");
+ return ret;
+ }
+
+ mutex_lock(&ddata->lock);
+ cur_state = pwm->state;
+ enabled = cur_state.enabled;
+
+ duty_cycle = state->duty_cycle;
+ if (!state->enabled)
+ duty_cycle = 0;
+
+ /*
+ * The problem of output producing mixed setting as mentioned at top,
+ * occurs here. To minimize the window for this problem, we are
+ * calculating the register values first and then writing them
+ * consecutively
+ */
+ num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
+ frac = DIV_ROUND_CLOSEST_ULL(num, state->period);
+ /* The hardware cannot generate a 100% duty cycle */
+ frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
+
+ if (state->period != ddata->approx_period) {
+ if (ddata->user_count != 1) {
+ ret = -EBUSY;
+ goto exit;
+ }
+ ddata->approx_period = state->period;
+ pwm_sifive_update_clock(ddata, clk_get_rate(ddata->clk));
+ }
+
+ writel(frac, ddata->regs + PWM_SIFIVE_PWMCMP0 +
+ pwm->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
+
+ if (state->enabled != enabled)
+ pwm_sifive_enable(chip, state->enabled);
+
+exit:
+ clk_disable(ddata->clk);
+ mutex_unlock(&ddata->lock);
+ return ret;
+}
+
+static const struct pwm_ops pwm_sifive_ops = {
+ .request = pwm_sifive_request,
+ .free = pwm_sifive_free,
+ .get_state = pwm_sifive_get_state,
+ .apply = pwm_sifive_apply,
+ .owner = THIS_MODULE,
+};
+
+static int pwm_sifive_clock_notifier(struct notifier_block *nb,
+ unsigned long event, void *data)
+{
+ struct clk_notifier_data *ndata = data;
+ struct pwm_sifive_ddata *ddata =
+ container_of(nb, struct pwm_sifive_ddata, notifier);
+
+ if (event == POST_RATE_CHANGE)
+ pwm_sifive_update_clock(ddata, ndata->new_rate);
+
+ return NOTIFY_OK;
+}
+
+static int pwm_sifive_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct pwm_sifive_ddata *ddata;
+ struct pwm_chip *chip;
+ struct resource *res;
+ int ret;
+
+ ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
+ if (!ddata)
+ return -ENOMEM;
+
+ mutex_init(&ddata->lock);
+ chip = &ddata->chip;
+ chip->dev = dev;
+ chip->ops = &pwm_sifive_ops;
+ chip->of_xlate = of_pwm_xlate_with_flags;
+ chip->of_pwm_n_cells = 3;
+ chip->base = -1;
+ chip->npwm = 4;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ ddata->regs = devm_ioremap_resource(dev, res);
+ if (IS_ERR(ddata->regs)) {
+ dev_err(dev, "Unable to map IO resources\n");
+ return PTR_ERR(ddata->regs);
+ }
+
+ ddata->clk = devm_clk_get(dev, NULL);
+ if (IS_ERR(ddata->clk)) {
+ if (PTR_ERR(ddata->clk) != -EPROBE_DEFER)
+ dev_err(dev, "Unable to find controller clock\n");
+ return PTR_ERR(ddata->clk);
+ }
+
+ ret = clk_prepare_enable(ddata->clk);
+ if (ret) {
+ dev_err(dev, "failed to enable clock for pwm: %d\n", ret);
+ return ret;
+ }
+
+ /* Watch for changes to underlying clock frequency */
+ ddata->notifier.notifier_call = pwm_sifive_clock_notifier;
+ ret = clk_notifier_register(ddata->clk, &ddata->notifier);
+ if (ret) {
+ dev_err(dev, "failed to register clock notifier: %d\n", ret);
+ goto disable_clk;
+ }
+
+ ret = pwmchip_add(chip);
+ if (ret < 0) {
+ dev_err(dev, "cannot register PWM: %d\n", ret);
+ goto unregister_clk;
+ }
+
+ platform_set_drvdata(pdev, ddata);
+ dev_dbg(dev, "SiFive PWM chip registered %d PWMs\n", chip->npwm);
+
+ return 0;
+
+unregister_clk:
+ clk_notifier_unregister(ddata->clk, &ddata->notifier);
+disable_clk:
+ clk_disable_unprepare(ddata->clk);
+
+ return ret;
+}
+
+static int pwm_sifive_remove(struct platform_device *dev)
+{
+ struct pwm_sifive_ddata *ddata = platform_get_drvdata(dev);
+ bool is_enabled = false;
+ struct pwm_device *pwm;
+ int ret, ch;
+
+ ret = pwmchip_remove(&ddata->chip);
+ clk_notifier_unregister(ddata->clk, &ddata->notifier);
+
+ for (ch = 0; ch < ddata->chip.npwm; ch++) {
+ pwm = &ddata->chip.pwms[ch];
+ if (pwm->state.enabled) {
+ is_enabled = true;
+ break;
+ }
+ }
+ if (is_enabled)
+ clk_disable(ddata->clk);
+ clk_disable_unprepare(ddata->clk);
+ return ret;
+}
+
+static const struct of_device_id pwm_sifive_of_match[] = {
+ { .compatible = "sifive,pwm0" },
+ {},
+};
+MODULE_DEVICE_TABLE(of, pwm_sifive_of_match);
+
+static struct platform_driver pwm_sifive_driver = {
+ .probe = pwm_sifive_probe,
+ .remove = pwm_sifive_remove,
+ .driver = {
+ .name = "pwm-sifive",
+ .of_match_table = pwm_sifive_of_match,
+ },
+};
+module_platform_driver(pwm_sifive_driver);
+
+MODULE_DESCRIPTION("SiFive PWM driver");
+MODULE_LICENSE("GPL v2");
--
1.9.1