Re: [PATCH v7 2/2] pwm: sifive: Add a driver for SiFive SoC PWM

From: Uwe Kleine-König
Date: Thu Feb 21 2019 - 16:16:18 EST

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In reply to: Yash Shah: "[PATCH v7 2/2] pwm: sifive: Add a driver for SiFive SoC PWM"
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On Thu, Feb 21, 2019 at 02:41:41PM +0530, Yash Shah wrote:
> Adds a PWM driver for PWM chip present in SiFive's HiFive Unleashed SoC.
>
> Signed-off-by: Wesley W. Terpstra <wesley@xxxxxxxxxx>
> [Atish: Various fixes and code cleanup]
> Signed-off-by: Atish Patra <atish.patra@xxxxxxx>
> Signed-off-by: Yash Shah <yash.shah@xxxxxxxxxx>
> ---
> drivers/pwm/Kconfig | 11 ++
> drivers/pwm/Makefile | 1 +
> drivers/pwm/pwm-sifive.c | 346 +++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 358 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..8f29283d
> --- /dev/null
> +++ b/drivers/pwm/pwm-sifive.c
> @@ -0,0 +1,346 @@
> +// 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 generaets only inverted output.

s/generaets/generates/

> + */
> +#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 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 0
> +#define PWM_SIFIVE_PWMCFG_STICKY 8
> +#define PWM_SIFIVE_PWMCFG_ZERO_CMP 9
> +#define PWM_SIFIVE_PWMCFG_DEGLITCH 10
> +#define PWM_SIFIVE_PWMCFG_EN_ALWAYS BIT(12)
> +#define PWM_SIFIVE_PWMCFG_EN_ONCE 13
> +#define PWM_SIFIVE_PWMCFG_CENTER 16
> +#define PWM_SIFIVE_PWMCFG_GANG 24
> +#define PWM_SIFIVE_PWMCFG_IP 28
> +
> +/* PWM_SIFIVE_SIZE_PWMCMP is used to calculate offset for pwmcmpX registers */
> +#define PWM_SIFIVE_SIZE_PWMCMP 4
> +#define PWM_SIFIVE_CMPWIDTH 16
> +
> +struct pwm_sifive_ddata {
> + struct pwm_chip chip;
> + struct mutex lock; /* lock to protect user_count and active_user */
> + struct notifier_block notifier;
> + struct clk *clk;
> + void __iomem *regs;
> + unsigned int real_period;
> + int user_count;
> + int active_user;
> +};
> +
> +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 *dev)
> +{
> + struct pwm_sifive_ddata *pwm = pwm_sifive_chip_to_ddata(chip);
> +
> + mutex_lock(&pwm->lock);
> + pwm->user_count++;
> + mutex_unlock(&pwm->lock);
> +
> + return 0;
> +}
> +
> +static void pwm_sifive_free(struct pwm_chip *chip, struct pwm_device *dev)
> +{
> + struct pwm_sifive_ddata *pwm = pwm_sifive_chip_to_ddata(chip);
> +
> + mutex_lock(&pwm->lock);
> + pwm->user_count--;
> + mutex_unlock(&pwm->lock);
> +}
> +
> +static void pwm_sifive_update_clock(struct pwm_sifive_ddata *pwm,
> + unsigned long rate)
> +{
> + u32 val;
> + unsigned long num;
> + /* (1 << (PWM_SIFIVE_CMPWIDTH+scale)) * 10^9/rate = real_period */
> + unsigned long scale_pow =
> + div64_ul(pwm->real_period * (u64)rate, NSEC_PER_SEC);
> + int scale = clamp(ilog2(scale_pow) - PWM_SIFIVE_CMPWIDTH, 0, 0xf);
> +
> + val = PWM_SIFIVE_PWMCFG_EN_ALWAYS | (scale << PWM_SIFIVE_PWMCFG_SCALE);
> + writel(val, pwm->regs + PWM_SIFIVE_PWMCFG);
> +
> + /* As scale <= 15 the shift operation cannot overflow. */
> + num = 1000000000ULL << (PWM_SIFIVE_CMPWIDTH + scale);

Huh, num is only an unsigned long, so you're loosing some bits here.

> + pwm->real_period = div64_ul(num, rate);
> + dev_dbg(pwm->chip.dev, "New real_period = %u ns\n", pwm->real_period);
> +}
> +
> +static void pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *dev,
> + struct pwm_state *state)
> +{
> + struct pwm_sifive_ddata *pwm = pwm_sifive_chip_to_ddata(chip);
> + u32 duty, val;
> + unsigned long num;

This should also be unsigned long long.

> + duty = readl(pwm->regs + PWM_SIFIVE_PWMCMP0 +
> + dev->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
> +
> + val = readl(pwm->regs + PWM_SIFIVE_PWMCFG);
> + state->enabled = duty > 0;
> +
> + val &= 0x0F;
> + num = 1000000000ULL << (PWM_SIFIVE_CMPWIDTH + val);
> + pwm->real_period = div64_ul(num, clk_get_rate(pwm->clk));

clk_get_rate must only be called if the clock is enabled.

> + state->period = pwm->real_period;
> + state->duty_cycle =
> + (u64)duty * pwm->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 *pwm = pwm_sifive_chip_to_ddata(chip);
> + int val, ret;
> +
> + if (enable) {
> + ret = clk_enable(pwm->clk);
> + if (ret) {
> + dev_err(pwm->chip.dev, "Enable clk failed:%d\n", ret);
> + return ret;
> + }
> + }
> +
> + val = readl(pwm->regs + PWM_SIFIVE_PWMCFG);
> +
> + if (enable)
> + val |= PWM_SIFIVE_PWMCFG_EN_ALWAYS;
> + else
> + val &= ~PWM_SIFIVE_PWMCFG_EN_ALWAYS;
> +
> + writel(val, pwm->regs + PWM_SIFIVE_PWMCFG);
> +
> + if (!enable)
> + clk_disable(pwm->clk);

This might come too early as after clearing PWM_SIFIVE_PWMCFG_EN_ALWAYS
the period has to finish first.

> + return 0;
> +}
> +
> +static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *dev,
> + struct pwm_state *state)
> +{
> + struct pwm_sifive_ddata *pwm = pwm_sifive_chip_to_ddata(chip);
> + unsigned int duty_cycle, x;
> + u32 frac;
> + struct pwm_state cur_state;
> + bool enabled;
> + int ret;
> + unsigned long num;
> +
> + pwm_get_state(dev, &cur_state);
> + enabled = cur_state.enabled;
> +
> + if (state->polarity != PWM_POLARITY_INVERSED)
> + return -EINVAL;
> +
> + if (state->period != cur_state.period) {
> + mutex_lock(&pwm->lock);

This lock is too late. You need to protect pwm_get_state() already.

> + if (pwm->user_count != 1) {
> + mutex_unlock(&pwm->lock);
> + return -EINVAL;
> + }
> + pwm->real_period = state->period;
> + pwm_sifive_update_clock(pwm, clk_get_rate(pwm->clk));
> + mutex_unlock(&pwm->lock);

This is also wrong.
> + }
> +
> + duty_cycle = state->duty_cycle;
> + if (!state->enabled)
> + duty_cycle = 0;
> +
> + x = 1U << PWM_SIFIVE_CMPWIDTH;
> + num = (u64)duty_cycle * x + x / 2;
> + frac = div_u64(num, state->period);
> + /* The hardware cannot generate a 100% duty cycle */
> + frac = min(frac, x - 1);
> +
> + writel(frac, pwm->regs + PWM_SIFIVE_PWMCMP0 +
> + dev->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
> +
> + if (!state->enabled && enabled) {
> + mutex_lock(&pwm->lock);
> + if (pwm->active_user == 1) {

You count in .active_user something that clk_enable/clk_disable could
already do for you. (Just keep PWM_SIFIVE_PWMCFG_EN_ALWAYS set, the
generated wave forms are identical apart from the first enable taking
more time without tracking active_user)

> + ret = pwm_sifive_enable(chip, false);
> + if (ret) {
> + mutex_unlock(&pwm->lock);
> + return ret;
> + }
> + }
> + pwm->active_user--;
> + mutex_unlock(&pwm->lock);
> + enabled = false;
> + }
> +
> + if (state->enabled != enabled) {

I think using

if (state->enabled && !enabled) {

is equivalent but clearer.

> + mutex_lock(&pwm->lock);
> + if (pwm->active_user == 0) {
> + ret = pwm_sifive_enable(chip, state->enabled);
> + if (ret) {
> + mutex_unlock(&pwm->lock);
> + return ret;
> + }
> + }
> + pwm->active_user++;
> + mutex_unlock(&pwm->lock);
> + }
> +
> + return 0;
> +}
> +
> +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 *pwm =
> + container_of(nb, struct pwm_sifive_ddata, notifier);
> +
> + if (event == POST_RATE_CHANGE)
> + pwm_sifive_update_clock(pwm, ndata->new_rate);
> +
> + return NOTIFY_OK;
> +}
> +
> +static int pwm_sifive_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct pwm_sifive_ddata *pwm;
> + struct pwm_chip *chip;
> + struct resource *res;
> + int ret;
> +
> + pwm = devm_kzalloc(dev, sizeof(*pwm), GFP_KERNEL);
> + if (!pwm)
> + return -ENOMEM;
> +
> + mutex_init(&pwm->lock);
> + chip = &pwm->chip;
> + chip->dev = dev;
> + chip->ops = &pwm_sifive_ops;
> + chip->of_pwm_n_cells = 3;
> + chip->base = -1;
> + chip->npwm = 4;
> +
> + 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 = pwm_sifive_clock_notifier;
> + ret = clk_notifier_register(pwm->clk, &pwm->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;
> + }
> +
> + /* Enable PWM */
> + ret = pwm_sifive_enable(chip, true);
> + if (ret)
> + dev_warn(dev, "cannot Enable PWM: %d\n", ret);

s/E/e/

> +
> + if (!pwm_is_enabled(pwm->chip.pwms))
> + clk_disable(pwm->clk);

You check only the first pwm here, while you must not disable the clock
if any pwm is running, right?

> +
> + platform_set_drvdata(pdev, pwm);
> + dev_dbg(dev, "SiFive PWM chip registered %d PWMs\n", chip->npwm);
> +
> + return 0;
> +
> +unregister_clk:
> + clk_notifier_unregister(pwm->clk, &pwm->notifier);
> +disable_clk:
> + clk_disable_unprepare(pwm->clk);
> +
> + return ret;
> +}
> +
> +static int pwm_sifive_remove(struct platform_device *dev)
> +{
> + struct pwm_sifive_ddata *pwm = platform_get_drvdata(dev);
> + int ret;
> +
> + ret = pwmchip_remove(&pwm->chip);
> + clk_notifier_unregister(pwm->clk, &pwm->notifier);
> + if (!pwm_is_enabled(pwm->chip.pwms))
> + clk_disable(pwm->clk);

I think this must be:

if (any pwm is enabled)
clk_disable(pwm->clk);

> + clk_unprepare(pwm->clk);
> + return ret;
> +}

Best regards
Uwe

--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |

Next message: Zi Yan: "Re: [RFC PATCH 01/31] mm: migrate: Add exchange_pages to exchange two lists of pages."
Previous message: Jonas Gorski: "Re: [PATCH] MIPS: ingenic: Add support for appended devicetree"
In reply to: Yash Shah: "[PATCH v7 2/2] pwm: sifive: Add a driver for SiFive SoC PWM"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]