Date:   Tue, 21 Dec 2021 15:20:50 +0800
From:   hammer hsieh <hammerh0314@...il.com>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     thierry.reding@...il.com, lee.jones@...aro.org, robh+dt@...nel.org,
        linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, wells.lu@...plus.com,
        Hammer Hsieh <hammer.hsieh@...plus.com>
Subject: Re: [PATCH v1 2/2] pwm:sunplus-pwm:Add Sunplus SoC PWM Driver

Hi: Uwe:

Thanks for your review.
Please see my response below.

Regards,
Hammer Hsieh

Uwe Kleine-König <u.kleine-koenig@...gutronix.de> 於 2021年12月17日 週五 下午11:28寫道：
>
> Hello,
>
> On Fri, Dec 17, 2021 at 07:46:08PM +0800, Hammer Hsieh wrote:
> > Add Sunplus SoC PWM Driver
> >
> > Signed-off-by: Hammer Hsieh <hammer.hsieh@...plus.com>
> > ---
> >  MAINTAINERS               |   1 +
> >  drivers/pwm/Kconfig       |  11 +++
> >  drivers/pwm/Makefile      |   1 +
> >  drivers/pwm/pwm-sunplus.c | 192 ++++++++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 205 insertions(+)
> >  create mode 100644 drivers/pwm/pwm-sunplus.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 721ed79..1c9e3c5 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -18246,6 +18246,7 @@ SUNPLUS PWM DRIVER
> >  M:   Hammer Hsieh <hammer.hsieh@...plus.com>
> >  S:   Maintained
> >  F:   Documentation/devicetree/bindings/pwm/pwm-sunplus.yaml
> > +F:   drivers/pwm/pwm-sunplus.c
> >
> >  SUPERH
> >  M:   Yoshinori Sato <ysato@...rs.sourceforge.jp>
> > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> > index 21e3b05..9df5d5f 100644
> > --- a/drivers/pwm/Kconfig
> > +++ b/drivers/pwm/Kconfig
> > @@ -526,6 +526,17 @@ config PWM_SPRD
> >         To compile this driver as a module, choose M here: the module
> >         will be called pwm-sprd.
> >
> > +config PWM_SUNPLUS
> > +     tristate "Sunplus PWM support"
> > +     depends on ARCH_SUNPLUS || COMPILE_TEST
> > +     depends on HAS_IOMEM && OF
> > +     help
> > +       Generic PWM framework driver for the PWM controller on
> > +       Sunplus SoCs.
> > +
> > +       To compile this driver as a module, choose M here: the module
> > +       will be called pwm-sunplus.
> > +
> >  config PWM_STI
> >       tristate "STiH4xx PWM support"
> >       depends on ARCH_STI || COMPILE_TEST
> > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> > index 708840b..be58616 100644
> > --- a/drivers/pwm/Makefile
> > +++ b/drivers/pwm/Makefile
> > @@ -53,6 +53,7 @@ obj-$(CONFIG_PWM_STM32)             += pwm-stm32.o
> >  obj-$(CONFIG_PWM_STM32_LP)   += pwm-stm32-lp.o
> >  obj-$(CONFIG_PWM_STMPE)              += pwm-stmpe.o
> >  obj-$(CONFIG_PWM_SUN4I)              += pwm-sun4i.o
> > +obj-$(CONFIG_PWM_SUNPLUS)    += pwm-sunplus.o
> >  obj-$(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-sunplus.c b/drivers/pwm/pwm-sunplus.c
> > new file mode 100644
> > index 0000000..0ae59fc
> > --- /dev/null
> > +++ b/drivers/pwm/pwm-sunplus.c
> > @@ -0,0 +1,192 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * PWM device driver for SUNPLUS SoCs
> > + *
> > + * Author: Hammer Hsieh <hammer.hsieh@...plus.com>
> > + */
>
> Please add a section here about your hardware limitations. Please stick
> to the format used in e.g. pwm-sifive.c. That is a block starting with
>
>  * Limitations:
>
> and then a list of issues. One such item is: Only supports normal
> polarity.
>
ok, will modify it.

> > +#include <linux/clk.h>
> > +#include <linux/io.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pwm.h>
> > +
> > +#define PWM_SUP_CONTROL0     0x000
> > +#define PWM_SUP_CONTROL1     0x004
> > +#define PWM_SUP_FREQ_BASE    0x008
> > +#define PWM_SUP_DUTY_BASE    0x018
> > +#define PWM_SUP_FREQ(ch)     (PWM_SUP_FREQ_BASE + 4 * (ch))
> > +#define PWM_SUP_DUTY(ch)     (PWM_SUP_DUTY_BASE + 4 * (ch))
> > +#define PWM_SUP_FREQ_MAX     GENMASK(15, 0)
> > +#define PWM_SUP_DUTY_MAX     GENMASK(7, 0)
> > +
> > +#define PWM_SUP_NUM          4
> > +#define PWM_BYPASS_BIT_SHIFT 8
> > +#define PWM_DD_SEL_BIT_SHIFT 8
> > +#define PWM_SUP_FREQ_SCALER  256
> > +
> > +struct sunplus_pwm {
> > +     struct pwm_chip chip;
> > +     void __iomem *base;
> > +     struct clk *clk;
> > +};
> > +
> > +static inline struct sunplus_pwm *to_sunplus_pwm(struct pwm_chip *chip)
> > +{
> > +     return container_of(chip, struct sunplus_pwm, chip);
> > +}
> > +
> > +static void sunplus_reg_init(void __iomem *base)
> > +{
> > +     u32 i, value;
> > +
> > +     /* turn off all pwm channel output */
> > +     value = readl(base + PWM_SUP_CONTROL0);
> > +     value &= ~GENMASK((PWM_SUP_NUM - 1), 0);
> > +     writel(value, base + PWM_SUP_CONTROL0);
> > +
> > +     /* init all pwm channel clock source */
> > +     value = readl(base + PWM_SUP_CONTROL1);
> > +     value |= GENMASK((PWM_SUP_NUM - 1), 0);
> > +     writel(value, base + PWM_SUP_CONTROL1);
> > +
> > +     /* init all freq and duty setting */
> > +     for (i = 0; i < PWM_SUP_NUM; i++) {
> > +             writel(0, base + PWM_SUP_FREQ(i));
> > +             writel(0, base + PWM_SUP_DUTY(i));
> > +     }
>
> Please keep the PWM in their boot-up state. That is, if the bootloader
> enabled a display with a bootsplash, don't disable the backlight when
> the PWM driver loads.
>

ok, will remove init reg code.

> > +}
> > +
> > +static int sunplus_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> > +                          const struct pwm_state *state)
> > +{
> > +     struct sunplus_pwm *priv = to_sunplus_pwm(chip);
> > +     u32 period_ns, duty_ns, value;
> > +     u32 dd_freq, duty;
> > +     u64 tmp;
> > +
>
>         if (state->polarity != PWM_POLARITY_NORMAL)
>                 return -EINVAL;
>
> > +     if (!state->enabled) {
> > +             value = readl(priv->base + PWM_SUP_CONTROL0);
> > +             value &= ~BIT(pwm->hwpwm);
> > +             writel(value, priv->base + PWM_SUP_CONTROL0);
> > +             return 0;
> > +     }
> > +
> > +     period_ns = state->period;
>
> state->period is an u64, so you might loose precision here.
>
> > +     duty_ns = state->duty_cycle;
>
> ditto
>
> > +
> > +     /* cal pwm freq and check value under range */
> > +     tmp = clk_get_rate(priv->clk) * (u64)period_ns;
>
> This might overflow?
>
> > +     tmp = DIV_ROUND_CLOSEST_ULL(tmp, NSEC_PER_SEC);
> > +     tmp = DIV_ROUND_CLOSEST_ULL(tmp, PWM_SUP_FREQ_SCALER);
>
> In general you should pick the highest period that isn't bigger than the
> requested period. I didn't check in detail, but using round-closest is a
> strong hint that you get that wrong.
>
> > +     dd_freq = (u32)tmp;
> > +
> > +     if (dd_freq == 0)
> > +             return -EINVAL;
> > +
> > +     if (dd_freq > PWM_SUP_FREQ_MAX)
> > +             dd_freq = PWM_SUP_FREQ_MAX;
> > +
> > +     writel(dd_freq, priv->base + PWM_SUP_FREQ(pwm->hwpwm));
> > +
> > +     /* cal and set pwm duty */
> > +     value = readl(priv->base + PWM_SUP_CONTROL0);
> > +     value |= BIT(pwm->hwpwm);
> > +     if (duty_ns == period_ns) {
> > +             value |= BIT(pwm->hwpwm + PWM_BYPASS_BIT_SHIFT);
> > +             duty = PWM_SUP_DUTY_MAX;
> > +     } else {
> > +             value &= ~BIT(pwm->hwpwm + PWM_BYPASS_BIT_SHIFT);
> > +             tmp = (u64)duty_ns * PWM_SUP_FREQ_SCALER + (period_ns >> 1);
> > +             tmp = DIV_ROUND_CLOSEST_ULL(tmp, (u64)period_ns);
> > +             duty = (u32)tmp;
> > +             duty |= (pwm->hwpwm << PWM_DD_SEL_BIT_SHIFT);
>
> This is also more inexact than necessary. In general don't use period_ns
> in the calculation of duty register settings. As with period you're
> supposed to pick the biggest possible dutycycle not bigger than the
> requested value.
>
> Consider a PWM that with register P = P and register D = D implements a
> PWM output with period = 1000 * P ns and duty_cycle = 1000 * D ns
>
> For a request of period = 39900 and duty_cycle = 12100, you have to pick
> P = 39 and D = 12. However P * duty_ns / period_ns = 11.82 ...
>

static int sunplus_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
     const struct pwm_state *state)
{
  struct sunplus_pwm *priv = to_sunplus_pwm(chip);
  u32 dd_freq, duty, value, value1;
  u64 period_ns, duty_ns, tmp;
  u64 period_ns_max;

  if (state->polarity != pwm->state.polarity)
  return -EINVAL;

  if (!state->enabled) {
  /* disable pwm channel output */
  value = readl(priv->base + PWM_SUP_CONTROL0);
  value &= ~BIT(pwm->hwpwm);
  writel(value, priv->base + PWM_SUP_CONTROL0);
  /* disable pwm channel clk source */
  value = readl(priv->base + PWM_SUP_CONTROL1);
  value &= ~BIT(pwm->hwpwm);
  writel(value, priv->base + PWM_SUP_CONTROL1);
  return 0;
  }

  tmp = PWM_SUP_FREQ_SCALER * NSEC_PER_SEC;
  tmp = DIV64_U64_ROUND_CLOSEST(tmp, clk_get_rate(priv->clk));
  period_ns_max = PWM_SUP_FREQ_MAX * tmp;

  if (state->period > period_ns_max)
    return -EINVAL;

  period_ns = state->period;
  duty_ns = state->duty_cycle;

  /* cal pwm freq and check value under range */
  tmp = DIV64_U64_ROUND_CLOSEST(clk_get_rate(priv->clk), PWM_SUP_FREQ_SCALER);
  tmp = tmp * period_ns >> 10;
  tmp = DIV64_U64_ROUND_CLOSEST(tmp, NSEC_PER_SEC >> 10);
  dd_freq = (u32)tmp;

  if (dd_freq == 0)
    return -EINVAL;

  if (dd_freq > PWM_SUP_FREQ_MAX)
    dd_freq = PWM_SUP_FREQ_MAX;

  writel(dd_freq, priv->base + PWM_SUP_FREQ(pwm->hwpwm));

  /* cal and set pwm duty */
  value = readl(priv->base + PWM_SUP_CONTROL0);
  value |= BIT(pwm->hwpwm);
  value1 = readl(priv->base + PWM_SUP_CONTROL1);
  value1 |= BIT(pwm->hwpwm);
  if (duty_ns == period_ns) {
  value |= BIT(pwm->hwpwm + PWM_BYPASS_BIT_SHIFT);
  duty = PWM_SUP_DUTY_MAX;
  } else {
  value &= ~BIT(pwm->hwpwm + PWM_BYPASS_BIT_SHIFT);
  tmp = (duty_ns >> 10) * PWM_SUP_FREQ_SCALER;
  tmp = DIV64_U64_ROUND_CLOSEST(tmp, (period_ns >> 10));
  duty = (u32)tmp;
  duty |= (pwm->hwpwm << PWM_DD_SEL_BIT_SHIFT);
  }
  writel(value, priv->base + PWM_SUP_CONTROL0);
  writel(value1, priv->base + PWM_SUP_CONTROL1);
  writel(duty, priv->base + PWM_SUP_DUTY(pwm->hwpwm));

  return 0;
}

While I turn on PWM_DEBUG.
I still can see the warning message.
"sunplus-pwm 9c007a00.pwm: .apply is not idempotent (ena=1 pol=0
9998240/19996480)->(ena=1 pol=0 9996976/19993952)
I'm not sure if it is an issue or not.
echo 20000000 > period
echo 10000000 > duty_cycle
echo 1 > enable
get_state: Calculate reg value to state->period and state->duty_cycle.
apply: Calculate state->period and state->duty_cycle to reg value.
Can't match always.

> > +     }
> > +     writel(value, priv->base + PWM_SUP_CONTROL0);
> > +     writel(duty, priv->base + PWM_SUP_DUTY(pwm->hwpwm));
> > +
> > +     return 0;
> > +}
> > +
> > +static void sunplus_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> > +                               struct pwm_state *state)
> > +{
> > +     struct sunplus_pwm *priv = to_sunplus_pwm(chip);
> > +     u32 value;
> > +
> > +     value = readl(priv->base + PWM_SUP_CONTROL0);
> > +
> > +     if (value & BIT(pwm->hwpwm))
> > +             state->enabled = true;
> > +     else
> > +             state->enabled = false;
>
> This looks incomplete. Please enable PWM_DEBUG during your tests and
> address all output generated by that.
>
> As the general idea is that passing the result from .get_state() to
> .apply shouldn't modify the output, you have (in general) round up
> divisions in .get_state().

static void sunplus_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
  struct pwm_state *state)
{
  struct sunplus_pwm *priv = to_sunplus_pwm(chip);
  u32 value, freq, duty;
  u64 tmp, rate;

  rate = clk_get_rate(priv->clk);
  value = readl(priv->base + PWM_SUP_CONTROL0);
  freq = readl(priv->base + PWM_SUP_FREQ(pwm->hwpwm));
  duty = readl(priv->base + PWM_SUP_DUTY(pwm->hwpwm));
  duty &= ~GENMASK(9,8);

  tmp = PWM_SUP_FREQ_SCALER * NSEC_PER_SEC;
  tmp = DIV64_U64_ROUND_CLOSEST(tmp, rate);
  state->period = (u64)freq * tmp;
  tmp = (u64)duty * state->period;
  state->duty_cycle = DIV64_U64_ROUND_CLOSEST(tmp, PWM_SUP_FREQ_SCALER);

  if (value & BIT(pwm->hwpwm))
    state->enabled = true;
  else
    state->enabled = false;

  state->polarity = PWM_POLARITY_NORMAL;
}

>
> > +}
> > +
> > +static const struct pwm_ops sunplus_pwm_ops = {
> > +     .apply = sunplus_pwm_apply,
> > +     .get_state = sunplus_pwm_get_state,
> > +     .owner = THIS_MODULE,
> > +};
> > +
> > +static int sunplus_pwm_probe(struct platform_device *pdev)
> > +{
> > +     struct device *dev = &pdev->dev;
> > +     struct sunplus_pwm *priv;
> > +     int ret;
> > +
> > +     priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> > +     if (!priv)
> > +             return -ENOMEM;
> > +
> > +     priv->base = devm_platform_ioremap_resource(pdev, 0);
> > +     if (IS_ERR(priv->base))
> > +             return PTR_ERR(priv->base);
> > +
> > +     priv->clk = devm_clk_get_optional(dev, NULL);
> > +     if (IS_ERR(priv->clk))
> > +             return dev_err_probe(dev, PTR_ERR(priv->clk),
> > +                                  "get pwm clock failed\n");
> > +
> > +     ret = clk_prepare_enable(priv->clk);
> > +     if (ret)
> > +             return ret;
> > +
> > +     ret = devm_add_action_or_reset(dev,
> > +                                    (void(*)(void *))clk_disable_unprepare,
> > +                                    priv->clk);
> > +     if (ret)
> > +             return ret;
> > +
> > +     priv->chip.dev = dev;
> > +     priv->chip.ops = &sunplus_pwm_ops;
> > +     priv->chip.npwm = PWM_SUP_NUM;
> > +
> > +     sunplus_reg_init(priv->base);
> > +
> > +     platform_set_drvdata(pdev, priv);
>
> This is unused, so please drop this.
>

ok, will modify it.

> > +
> > +     ret = devm_pwmchip_add(dev, &priv->chip);
> > +     if (ret < 0)
> > +             return dev_err_probe(dev, ret, "Cannot register sunplus PWM\n");
> > +
> > +     return 0;
> > +}
> > +
> > +static const struct of_device_id sunplus_pwm_of_match[] = {
> > +     { .compatible = "sunplus,sp7021-pwm", },
> > +     {}
> > +};
> > +MODULE_DEVICE_TABLE(of, sunplus_pwm_of_match);
> > +
> > +static struct platform_driver sunplus_pwm_driver = {
> > +     .probe          = sunplus_pwm_probe,
> > +     .driver         = {
> > +             .name   = "sunplus-pwm",
> > +             .of_match_table = sunplus_pwm_of_match,
> > +     },
> > +};
> > +module_platform_driver(sunplus_pwm_driver);
> > +
> > +MODULE_DESCRIPTION("Sunplus SoC PWM Driver");
> > +MODULE_AUTHOR("Hammer Hsieh <hammer.hsieh@...plus.com>");
> > +MODULE_LICENSE("GPL v2");
>
> "GPL" has the same semantic and is the more usual, so I suggest to use
> that one.
>
ok, will modify it.


> Best regards
> Uwe
>
> --
> Pengutronix e.K.                           | Uwe Kleine-König            |
> Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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