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

Yash Shah
2019-01-11T08:22:44Z

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 | 10 ++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-sifive.c | 246 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 257 insertions(+)
create mode 100644 drivers/pwm/pwm-sifive.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index a8f47df..3bcaf6a 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -380,6 +380,16 @@ 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
+ 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..7fee809
--- /dev/null
+++ b/drivers/pwm/pwm-sifive.c
@@ -0,0 +1,246 @@
+// 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
+ */
+#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>
+
+/* Register offsets */
+#define REG_PWMCFG 0x0
+#define REG_PWMCOUNT 0x8
+#define REG_PWMS 0x10
+#define REG_PWMCMP0 0x20
+
+/* PWMCFG fields */
+#define BIT_PWM_SCALE 0
+#define BIT_PWM_STICKY 8
+#define BIT_PWM_ZERO_ZMP 9
+#define BIT_PWM_DEGLITCH 10
+#define BIT_PWM_EN_ALWAYS 12
+#define BIT_PWM_EN_ONCE 13
+#define BIT_PWM0_CENTER 16
+#define BIT_PWM0_GANG 24
+#define BIT_PWM0_IP 28
+
+#define SIZE_PWMCMP 4
+#define MASK_PWM_SCALE 0xf
+
+struct sifive_pwm_device {
+ struct pwm_chip chip;
+ struct notifier_block notifier;
+ struct clk *clk;
+ void __iomem *regs;
+ unsigned int approx_period;
+ unsigned int real_period;
+};
+
+static inline struct sifive_pwm_device *to_sifive_pwm_chip(struct pwm_chip *c)
+{
+ return container_of(c, struct sifive_pwm_device, chip);
+}
+
+static void sifive_pwm_get_state(struct pwm_chip *chip, struct pwm_device *dev,
+ struct pwm_state *state)
+{
+ struct sifive_pwm_device *pwm = to_sifive_pwm_chip(chip);
+ u32 duty;
+
+ duty = readl(pwm->regs + REG_PWMCMP0 + dev->hwpwm * SIZE_PWMCMP);
+
+ state->period = pwm->real_period;
+ state->duty_cycle = ((u64)duty * pwm->real_period) >> 16;
+ state->polarity = PWM_POLARITY_INVERSED;
+ state->enabled = duty > 0;
+}
+
+static int sifive_pwm_apply(struct pwm_chip *chip, struct pwm_device *dev,
+ struct pwm_state *state)
+{
+ struct sifive_pwm_device *pwm = to_sifive_pwm_chip(chip);
+ unsigned int duty_cycle;
+ u32 frac;
+
+ if (state->polarity != PWM_POLARITY_INVERSED)
+ return -EINVAL;
+
+ duty_cycle = state->duty_cycle;
+ if (!state->enabled)
+ duty_cycle = 0;
+
+ frac = div_u64((u64)duty_cycle << 16, state->period);
+ frac = min(frac, 0xFFFFU);
+
+ writel(frac, pwm->regs + REG_PWMCMP0 + dev->hwpwm * SIZE_PWMCMP);
+
+ if (state->enabled)
+ sifive_pwm_get_state(chip, dev, state);
+
+ return 0;
+}
+
+static const struct pwm_ops sifive_pwm_ops = {
+ .get_state = sifive_pwm_get_state,
+ .apply = sifive_pwm_apply,
+ .owner = THIS_MODULE,
+};
+
+static struct pwm_device *sifive_pwm_xlate(struct pwm_chip *chip,
+ const struct of_phandle_args *args)
+{
+ struct sifive_pwm_device *pwm = to_sifive_pwm_chip(chip);
+ struct pwm_device *dev;
+
+ if (args->args[0] >= chip->npwm)
+ return ERR_PTR(-EINVAL);
+
+ dev = pwm_request_from_chip(chip, args->args[0], NULL);
+ if (IS_ERR(dev))
+ return dev;
+
+ /* The period cannot be changed on a per-PWM basis */
+ dev->args.period = pwm->real_period;
+ dev->args.polarity = PWM_POLARITY_NORMAL;
+ if (args->args[1] & PWM_POLARITY_INVERSED)
+ dev->args.polarity = PWM_POLARITY_INVERSED;
+
+ return dev;
+}
+
+static void sifive_pwm_update_clock(struct sifive_pwm_device *pwm,
+ unsigned long rate)
+{
+ /* (1 << (16+scale)) * 10^9/rate = real_period */
+ unsigned long scale_pow = (pwm->approx_period * (u64)rate) / 1000000000;
+ int scale = clamp(ilog2(scale_pow) - 16, 0, 0xf);
+
+ writel((1 << BIT_PWM_EN_ALWAYS) | (scale << BIT_PWM_SCALE),
+ pwm->regs + REG_PWMCFG);
+
+ /* As scale <= 15 the shift operation cannot overflow. */
+ pwm->real_period = div64_ul(1000000000ULL << (16 + scale), rate);
+ dev_dbg(pwm->chip.dev, "New real_period = %u ns\n", pwm->real_period);
+}
+
+static int sifive_pwm_clock_notifier(struct notifier_block *nb,
+ unsigned long event, void *data)
+{
+ struct clk_notifier_data *ndata = data;
+ struct sifive_pwm_device *pwm =
+ container_of(nb, struct sifive_pwm_device, notifier);
+
+ if (event == POST_RATE_CHANGE)
+ sifive_pwm_update_clock(pwm, ndata->new_rate);
+
+ return NOTIFY_OK;
+}
+
+static int sifive_pwm_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *node = pdev->dev.of_node;
+ struct sifive_pwm_device *pwm;
+ struct pwm_chip *chip;
+ struct resource *res;
+ int ret;
+
+ pwm = devm_kzalloc(dev, sizeof(*pwm), GFP_KERNEL);
+ if (!pwm)
+ return -ENOMEM;
+
+ chip = &pwm->chip;
+ chip->dev = dev;
+ chip->ops = &sifive_pwm_ops;
+ chip->of_xlate = sifive_pwm_xlate;
+ chip->of_pwm_n_cells = 2;
+ chip->base = -1;
+ chip->npwm = 4;
+
+ ret = of_property_read_u32(node, "sifive,approx-period-ns",
+ &pwm->approx_period);
+ if (ret < 0) {
+ dev_err(dev, "Unable to read sifive,approx-period from DTS\n");
+ return ret;
+ }
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ pwm->regs = devm_ioremap_resource(dev, res);
+ if (IS_ERR(pwm->regs)) {
+ dev_err(dev, "Unable to map IO resources\n");
+ return PTR_ERR(pwm->regs);
+ }
+
+ pwm->clk = devm_clk_get(dev, NULL);
+ if (IS_ERR(pwm->clk)) {
+ if (PTR_ERR(pwm->clk) != -EPROBE_DEFER)
+ dev_err(dev, "Unable to find controller clock\n");
+ return PTR_ERR(pwm->clk);
+ }
+
+ ret = clk_prepare_enable(pwm->clk);
+ if (ret) {
+ dev_err(dev, "failed to enable clock for pwm: %d\n", ret);
+ return ret;
+ }
+
+ /* Watch for changes to underlying clock frequency */
+ pwm->notifier.notifier_call = sifive_pwm_clock_notifier;
+ ret = clk_notifier_register(pwm->clk, &pwm->notifier);
+ if (ret) {
+ dev_err(dev, "failed to register clock notifier: %d\n", ret);
+ clk_disable_unprepare(pwm->clk);
+ return ret;
+ }
+
+ /* Initialize PWM config */
+ sifive_pwm_update_clock(pwm, clk_get_rate(pwm->clk));
+
+ ret = pwmchip_add(chip);
+ if (ret < 0) {
+ dev_err(dev, "cannot register PWM: %d\n", ret);
+ clk_notifier_unregister(pwm->clk, &pwm->notifier);
+ clk_disable_unprepare(pwm->clk);
+ return ret;
+ }
+
+ platform_set_drvdata(pdev, pwm);
+ dev_dbg(dev, "SiFive PWM chip registered %d PWMs\n", chip->npwm);
+
+ return 0;
+}
+
+static int sifive_pwm_remove(struct platform_device *dev)
+{
+ struct sifive_pwm_device *pwm = platform_get_drvdata(dev);
+ int ret;
+
+ ret = pwmchip_remove(&pwm->chip);
+ clk_notifier_unregister(pwm->clk, &pwm->notifier);
+ clk_disable_unprepare(pwm->clk);
+ return ret;
+}
+
+static const struct of_device_id sifive_pwm_of_match[] = {
+ { .compatible = "sifive,pwm0" },
+ { .compatible = "sifive,fu540-c000-pwm" },
+ {},
+};
+MODULE_DEVICE_TABLE(of, sifive_pwm_of_match);
+
+static struct platform_driver sifive_pwm_driver = {
+ .probe = sifive_pwm_probe,
+ .remove = sifive_pwm_remove,
+ .driver = {
+ .name = "pwm-sifive",
+ .of_match_table = sifive_pwm_of_match,
+ },
+};
+module_platform_driver(sifive_pwm_driver);
+
+MODULE_DESCRIPTION("SiFive PWM driver");
+MODULE_LICENSE("GPL v2");
--
1.9.1