Message-ID: <CAJRtX8T3GD-zu43-+U_rGQugqzGQQ-QbjHATV1NRdEMWevSUGw@mail.gmail.com>
Date: Tue, 5 Mar 2024 17:19:34 +0800
From: Jingbao Qiu <qiujingbao.dlmu@...il.com>
To: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc: robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, 
	paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu, 
	linux-pwm@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	dlan@...too.org, inochiama@...look.com
Subject: Re: [PATCH v4 2/2] pwm: sophgo: add pwm support for Sophgo CV1800 SoC

Hi Uwe,

On Mon, Mar 4, 2024 at 11:37 PM Uwe Kleine-König
<u.kleine-koenig@...gutronix.de> wrote:
>
> Hello,
>
> thanks for your patch.
>
> On Mon, Mar 04, 2024 at 05:02:48PM +0800, Jingbao Qiu wrote:
> > Implement the PWM driver for CV1800.
> >
> > Signed-off-by: Jingbao Qiu <qiujingbao.dlmu@...il.com>
> > ---
> >  drivers/pwm/Kconfig      |  10 ++
> >  drivers/pwm/Makefile     |   1 +
> >  drivers/pwm/pwm-cv1800.c | 314 +++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 325 insertions(+)
> >  create mode 100644 drivers/pwm/pwm-cv1800.c
> >
> > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> > index 4b956d661755..455f07af94f7 100644
> > --- a/drivers/pwm/Kconfig
> > +++ b/drivers/pwm/Kconfig
> > @@ -186,6 +186,16 @@ config PWM_CROS_EC
> >         PWM driver for exposing a PWM attached to the ChromeOS Embedded
> >         Controller.
> >
> > +config PWM_CV1800
> > +     tristate "Sophgo CV1800 PWM driver"
> > +     depends on ARCH_SOPHGO || COMPILE_TEST
> > +     help
> > +       Generic PWM framework driver for the Sophgo CV1800 series
> > +       SoCs.
> > +
> > +       To compile this driver as a module, build the dependecies
> > +       as modules, this will be called pwm-cv1800.
> > +
> >  config PWM_DWC_CORE
> >       tristate
> >       depends on HAS_IOMEM
> > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> > index c5ec9e168ee7..6c3c4a07a316 100644
> > --- a/drivers/pwm/Makefile
> > +++ b/drivers/pwm/Makefile
> > @@ -15,6 +15,7 @@ obj-$(CONFIG_PWM_CLK)               += pwm-clk.o
> >  obj-$(CONFIG_PWM_CLPS711X)   += pwm-clps711x.o
> >  obj-$(CONFIG_PWM_CRC)                += pwm-crc.o
> >  obj-$(CONFIG_PWM_CROS_EC)    += pwm-cros-ec.o
> > +obj-$(CONFIG_PWM_CV1800)     += pwm-cv1800.o
> >  obj-$(CONFIG_PWM_DWC_CORE)   += pwm-dwc-core.o
> >  obj-$(CONFIG_PWM_DWC)                += pwm-dwc.o
> >  obj-$(CONFIG_PWM_EP93XX)     += pwm-ep93xx.o
> > diff --git a/drivers/pwm/pwm-cv1800.c b/drivers/pwm/pwm-cv1800.c
> > new file mode 100644
> > index 000000000000..d5b31a2b7787
> > --- /dev/null
> > +++ b/drivers/pwm/pwm-cv1800.c
> > @@ -0,0 +1,314 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * pwm-cv1800.c: PWM driver for Sophgo cv1800
>
> Mentioning the filename in the file isn't very helpful. It's obvious
> information.

I will drop this line.

>
> > + * Author: Jingbao Qiu <qiujingbao.dlmu@...il.com>
> > + *
> > + * Limitations:
> > + * - It output low when PWM channel disabled.
> > + * - This pwm device supports dynamic loading of PWM parameters. When PWMSTART
> > + *   is written from 0 to 1, the register value (HLPERIODn, PERIODn) will be
> > + *   temporarily stored inside the PWM. If you want to dynamically change the
> > + *   waveform during PWM output, after writing the new value to HLPERIODn and
> > + *   PERIODn, write 1 and then 0 to PWMUPDATE[n] to make the new value effective.
> > + * - Supports up to Rate/2 output, and the lowest is about Rate/(2^30-1).
> > + * - By setting HLPERIODn to 0, can produce 100% duty cycle.
> > + * - This hardware could support inverted polarity. By default, the value of the
> > + *   POLARITY register is 0x0. This means that HLPERIOD represents the number
> > + *   of low level beats.
> > + * - This hardware supports input mode and output mode, implemented through the
> > + *   Output-Enable/OE register. However, this driver has not yet implemented
> > + *   capture callback.
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pwm.h>
> > +#include <linux/regmap.h>
> > +
> > +#define PWM_CV1800_HLPERIOD_BASE     0x00
> > +#define PWM_CV1800_PERIOD_BASE       0x04
> > +#define PWM_CV1800_POLARITY          0x40
> > +#define PWM_CV1800_START             0x44
> > +#define PWM_CV1800_DONE              0x48
> > +#define PWM_CV1800_UPDATE            0x4c
> > +#define PWM_CV1800_OE                0xd0
> > +
> > +#define PWM_CV1800_HLPERIOD(n)       (PWM_CV1800_HLPERIOD_BASE + ((n) * 0x08))
> > +#define PWM_CV1800_PERIOD(n)         (PWM_CV1800_PERIOD_BASE + ((n) * 0x08))
> > +
> > +#define PWM_CV1800_UPDATE_MASK(n)    (BIT(0) << (n))
> > +#define PWM_CV1800_OE_MASK(n)        (BIT(0) << (n))
> > +#define PWM_CV1800_START_MASK(n)     (BIT(0) << (n))
> > +#define PWM_CV1800_POLARITY_MASK(n)  (BIT(0) << (n))
> > +
> > +#define PWM_CV1800_OE_INPUT          0x00U
> > +#define PWM_CV1800_OE_OUTPUT(n)      (BIT(0) << (n))
> > +#define PWM_CV1800_MAXPERIOD         (BIT(30) - 1)
> > +#define PWM_CV1800_MINPERIOD         BIT(1)
>
> These are minimal and maximal values. I'd do
>
> #define PWM_CV1800_MAXPERIOD         0x3fffffff
> #define PWM_CV1800_MINPERIOD         2
>

I will fix it.

> > +#define PWM_CV1800_PERIOD_RESET      BIT(1)
> > +#define PWM_CV1800_HLPERIOD_RESET    BIT(0)
> > +#define PWM_CV1800_REG_DISABLE       0x00U
> > +#define PWM_CV1800_REG_ENABLE(n)     (BIT(0) << (n))
> > +#define PWM_CV1800_CHANNELS          4
> > +
> > +struct cv1800_pwm {
> > +     struct regmap *map;
> > +     struct clk *clk;
> > +     unsigned long clk_rate;
> > +};
> > +
> > +static inline struct cv1800_pwm *to_cv1800_pwm_dev(struct pwm_chip *chip)
> > +{
> > +     return pwmchip_get_drvdata(chip);
> > +}
> > +
> > +static const struct regmap_config cv1800_pwm_regmap_config = {
> > +     .reg_bits = 32,
> > +     .val_bits = 32,
> > +     .reg_stride = 4,
> > +};
> > +
> > +static int cv1800_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm,
> > +                          bool enable)
> > +{
> > +     struct cv1800_pwm *priv = to_cv1800_pwm_dev(chip);
> > +     u32 pwm_enable;
> > +
> > +     regmap_read(priv->map, PWM_CV1800_START, &pwm_enable);
> > +     pwm_enable &= PWM_CV1800_START_MASK(pwm->hwpwm);
> > +
> > +     /*
> > +      * If the parameters are changed during runtime, Register needs
> > +      * to be updated to take effect.
> > +      */
> > +     if (pwm_enable && enable) {
> > +             regmap_update_bits(priv->map, PWM_CV1800_UPDATE,
> > +                                PWM_CV1800_UPDATE_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_ENABLE(pwm->hwpwm));
> > +             regmap_update_bits(priv->map, PWM_CV1800_UPDATE,
> > +                                PWM_CV1800_UPDATE_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_DISABLE);
> > +     } else if (!pwm_enable && enable) {
> > +             regmap_update_bits(priv->map, PWM_CV1800_START,
> > +                                PWM_CV1800_START_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_ENABLE(pwm->hwpwm));
> > +     } else if (pwm_enable && !enable) {
> > +             regmap_update_bits(priv->map, PWM_CV1800_START,
> > +                                PWM_CV1800_START_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_DISABLE);
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +static void cv1800_pwm_set_polarity(struct pwm_chip *chip,
> > +                                 struct pwm_device *pwm,
> > +                                 enum pwm_polarity polarity)
> > +{
> > +     struct cv1800_pwm *priv = to_cv1800_pwm_dev(chip);
> > +
> > +     if (pwm->state.enabled)
> > +             cv1800_pwm_enable(chip, pwm, !pwm->state.enabled);
> > +
> > +     if (polarity == PWM_POLARITY_INVERSED)
> > +             regmap_update_bits(priv->map, PWM_CV1800_POLARITY,
> > +                                PWM_CV1800_POLARITY_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_ENABLE(pwm->hwpwm));
> > +     else
> > +             regmap_update_bits(priv->map, PWM_CV1800_POLARITY,
> > +                                PWM_CV1800_POLARITY_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_DISABLE);
>
> Wouldn't it be more natural to make this read:
>
>         if (polarity == PWM_POLARITY_INVERSED)
>                 regmap_update_bits(priv->map, PWM_CV1800_POLARITY,
>                                    PWM_CV1800_POLARITY_MASK(pwm->hwpwm),
>                                    PWM_CV1800_POLARITY_MASK(pwm->hwpwm));
>         else
>                 regmap_update_bits(priv->map, PWM_CV1800_POLARITY,
>                                    PWM_CV1800_POLARITY_MASK(pwm->hwpwm),
>                                    0);
>
> or even:
>
>         u32 polarity = 0;
>
>         if (polarity == PWM_POLARITY_INVERSED)
>                 polarity = PWM_CV1800_POLARITY_MASK(pwm->hwpwm);
>
>         regmap_update_bits(priv->map, PWM_CV1800_POLARITY,
>                            PWM_CV1800_POLARITY_MASK(pwm->hwpwm),
>                            polarity);
>
> ?
>

Good idea.  My code looks so bloated. I will fix it.

> > +}
> > +
> > +static void cv1800_pwm_set_oe(struct pwm_chip *chip, struct pwm_device *pwm,
> > +                           u32 mode)
> > +{
> > +     struct cv1800_pwm *priv = to_cv1800_pwm_dev(chip);
> > +     u32 state;
> > +
> > +     regmap_read(priv->map, PWM_CV1800_OE, &state);
> > +     state &= PWM_CV1800_OE_MASK(pwm->hwpwm);
> > +
> > +     if (state == mode)
> > +             return;
> > +
> > +     cv1800_pwm_enable(chip, pwm, false);
> > +
> > +     if (mode == PWM_CV1800_OE_INPUT)
> > +             regmap_update_bits(priv->map, PWM_CV1800_OE,
> > +                                PWM_CV1800_OE_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_DISABLE);
> > +     else if (mode == PWM_CV1800_OE_OUTPUT(pwm->hwpwm))
> > +             regmap_update_bits(priv->map, PWM_CV1800_OE,
> > +                                PWM_CV1800_OE_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_ENABLE(pwm->hwpwm));
> > +}
>
> What does this function do? A comment describing that would be good. I
> wonder about it being called unconditionally in .apply() below.

I will add a comment for this function.

>
> > +
> > +static int cv1800_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> > +                         const struct pwm_state *state)
> > +{
> > +     struct cv1800_pwm *priv = to_cv1800_pwm_dev(chip);
> > +     u32 period_val, hlperiod_val;
> > +     u64 tem;
> > +
> > +     cv1800_pwm_set_oe(chip, pwm, PWM_CV1800_OE_OUTPUT(pwm->hwpwm));
> > +
> > +     if (state->polarity != pwm->state.polarity)
> > +             cv1800_pwm_set_polarity(chip, pwm, state->polarity);
> > +
> > +     /*
> > +      * This hardware use PERIOD and HLPERIOD registers to represent PWM waves.
> > +      *
> > +      * The meaning of PERIOD is how many clock cycles (from the clock source)
> > +      * are used to represent PWM waves.
> > +      * PERIOD = rate(MHz) / target(MHz)
> > +      * PERIOD = period(ns) * rate(Hz) / NSEC_PER_SEC
> > +      */
> > +     tem = mul_u64_u64_div_u64(state->period, priv->clk_rate, NSEC_PER_SEC);
>
> What does "tem" stand for? Maybe "ticks" is a better name?

"ticks" looks better. I will use it.

>
> > +     if (tem < PWM_CV1800_MINPERIOD)
> > +             return -EINVAL;
> > +
> > +     if (tem > PWM_CV1800_MAXPERIOD)
> > +             tem = PWM_CV1800_MAXPERIOD;
> > +
> > +     period_val = (u32)tem;
> > +
> > +     /*
> > +      * The meaning of HLPERIOD is the number of beats in the low or high level
> > +      * of the PERIOD. When the value of the POLARITY register is 0, HLPERIOD
> > +      * represents a low level.
> > +      * HLPERIOD = period_val - rate(MHz) / duty(MHz)
> > +      * HLPERIOD = period_val - duty(ns) * rate(Hz) / NSEC_PER_SEC
>
> So HLPERIOD defines the second part of each period, right? This isn't
> considered in .get_state().

I am so sorry about this. I made a mess of the duty cycle.
According to the PWM_DEBUG, it can be inferred that configure the
biggest duty_cycle not
bigger than the requested value, so in .apply duty_cycle should round down and
in .get_state duty_cycle should round up. However, when the polarity is normal,
This hardware requires a low-level beat count. So the corrected code
is as follows.

in .apply()

ticks = mul_u64_u64_div_u64(state->duty_cycle , priv->clk_rate,NSEC_PER_SEC);
..
hlperiod_val =period_val- (u32)ticks;

in .get_state()

u32 hlperiod_val=0;

period_ns = DIV_ROUND_UP_ULL(period_val * NSEC_PER_SEC,priv->clk_rate);
duty_ns = DIV_ROUND_UP_ULL(hlperiod_val * period_ns, period_val);
hlperiod_val = period_ns - duty_ns;

I tested this code with PWM_DEBUG. no warning output. What do you
think about this?


>
> > +      */
> > +     tem = mul_u64_u64_div_u64(state->duty_cycle, priv->clk_rate,
> > +                               NSEC_PER_SEC);
> > +     if (tem > period_val)
> > +             return -EINVAL;
>
> if (tem > period_val)
>         tem = period_val;
>
> > +     hlperiod_val = period_val - (u32)tem;
>
> Wrong rounding I think. Did you test your driver with PWM_DEBUG enabled?

ditto.

>
> > +     regmap_write(priv->map, PWM_CV1800_PERIOD(pwm->hwpwm), period_val);
> > +     regmap_write(priv->map, PWM_CV1800_HLPERIOD(pwm->hwpwm), hlperiod_val);
> > +
> > +     cv1800_pwm_enable(chip, pwm, state->enabled);
> > +
> > +     return 0;
> > +}
> > +
> > +static int cv1800_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> > +                             struct pwm_state *state)
> > +{
> > +     struct cv1800_pwm *priv = to_cv1800_pwm_dev(chip);
> > +     u32 period_val, hlperiod_val;
> > +     u64 period_ns = 0;
> > +     u64 duty_ns = 0;
> > +     u32 enable = 0;
> > +     u32 polarity = 0;
> > +
> > +     regmap_read(priv->map, PWM_CV1800_PERIOD(pwm->hwpwm), &period_val);
> > +     regmap_read(priv->map, PWM_CV1800_HLPERIOD(pwm->hwpwm), &hlperiod_val);
> > +
> > +     if (period_val != PWM_CV1800_PERIOD_RESET ||
> > +         hlperiod_val != PWM_CV1800_HLPERIOD_RESET) {
> > +             period_ns = DIV_ROUND_UP_ULL(period_val * NSEC_PER_SEC,
> > +                                          priv->clk_rate);
> > +             duty_ns = DIV_ROUND_UP_ULL(hlperiod_val * period_ns, period_val);
> > +
> > +             regmap_read(priv->map, PWM_CV1800_START, &enable);
> > +             enable &= PWM_CV1800_START_MASK(pwm->hwpwm);
> > +
> > +             regmap_read(priv->map, PWM_CV1800_POLARITY, &polarity);
> > +             polarity &= PWM_CV1800_POLARITY_MASK(pwm->hwpwm);
> > +     }
> > +
> > +     state->period = period_ns;
> > +     state->duty_cycle = duty_ns;
> > +     state->enabled = enable;
> > +     state->polarity = polarity ? PWM_POLARITY_INVERSED : PWM_POLARITY_NORMAL;
> > +
> > +     return 0;
> > +}
> > +
> > +static const struct pwm_ops cv1800_pwm_ops = {
> > +     .apply = cv1800_pwm_apply,
> > +     .get_state = cv1800_pwm_get_state,
> > +};
> > +
> > +static void devm_clk_rate_exclusive_put(void *data)
> > +{
> > +     struct clk *clk = data;
> > +
> > +     clk_rate_exclusive_put(clk);
> > +}
> > +
> > +static int cv1800_pwm_probe(struct platform_device *pdev)
> > +{
> > +     struct device *dev = &pdev->dev;
> > +     struct cv1800_pwm *priv;
> > +     struct pwm_chip *chip;
> > +     void __iomem *base;
> > +     int ret;
> > +
> > +     chip = devm_pwmchip_alloc(dev, PWM_CV1800_CHANNELS, sizeof(*priv));
> > +     if (!chip)
> > +             return PTR_ERR(chip);
> > +     priv = to_cv1800_pwm_dev(chip);
> > +
> > +     base = devm_platform_ioremap_resource(pdev, 0);
> > +     if (IS_ERR(base))
> > +             return PTR_ERR(base);
> > +
> > +     priv->map = devm_regmap_init_mmio(&pdev->dev, base,
> > +                                       &cv1800_pwm_regmap_config);
> > +     if (IS_ERR(priv->map))
> > +             return PTR_ERR(priv->map);
> > +
> > +     priv->clk = devm_clk_get_enabled(&pdev->dev, NULL);
> > +     if (IS_ERR(priv->clk))
> > +             return dev_err_probe(&pdev->dev, PTR_ERR(priv->clk),
> > +                                  "clk not found\n");
> > +
> > +     ret = clk_rate_exclusive_get(priv->clk);
>
> There is a devm_clk_rate_exclusive_get() in next. Please make use of it.
> (See commit b0cde62e4c54)

I will use this branch.

>
> > +     if (ret)
> > +             return dev_err_probe(&pdev->dev, ret,
> > +                                  "failed to get exclusive rate\n");> > +
> > +     ret = devm_add_action_or_reset(&pdev->dev, devm_clk_rate_exclusive_put,
> > +                                    priv->clk);
> > +     if (ret) {
> > +             clk_rate_exclusive_put(priv->clk);
> > +             return ret;
> > +     }
> > +
> > +     priv->clk_rate = clk_get_rate(priv->clk);
> > +     if (!priv->clk_rate)
> > +             return dev_err_probe(&pdev->dev, -EINVAL,
> > +                                  "Invalid clock rate: %lu\n",
> > +                                  priv->clk_rate);
> > +
> > +     chip->ops = &cv1800_pwm_ops;
> > +
> > +     return devm_pwmchip_add(dev, chip);
>
> Error message if devm_pwmchip_add() fails, please.

I will fix it.

Thank you for your reply.

Best regards
Jingbao Qiu

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