Hi Thierry,
Thanks for your review.
On Fri, Apr 09, 2021 at 03:20:12PM +0200, Thierry Reding wrote:
> On Fri, Apr 09, 2021 at 06:07:09PM +0900, Nobuhiro Iwamatsu wrote:
> > Add driver for the PWM controller on Toshiba Visconti ARM SoC.
> >
> > Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@xxxxxxxxxxxxx>
> > ---
> > drivers/pwm/Kconfig | 9 ++
> > drivers/pwm/Makefile | 1 +
> > drivers/pwm/pwm-visconti.c | 193 +++++++++++++++++++++++++++++++++++++
> > 3 files changed, 203 insertions(+)
> > create mode 100644 drivers/pwm/pwm-visconti.c
>
> Looks good, but I have a few minor comments, see below.
>
> > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> > index 9a4f66ae8070..8ae68d6203fb 100644
> > --- a/drivers/pwm/Kconfig
> > +++ b/drivers/pwm/Kconfig
> > @@ -601,6 +601,15 @@ config PWM_TWL_LED
> > To compile this driver as a module, choose M here: the module
> > will be called pwm-twl-led.
> >
> > +config PWM_VISCONTI
> > + tristate "Toshiba Visconti PWM support"
> > + depends on ARCH_VISCONTI || COMPILE_TEST
> > + help
> > + PWM Subsystem driver support for Toshiba Visconti SoCs.
> > +
> > + To compile this driver as a module, choose M here: the module
> > + will be called pwm-visconti.
> > +
> > config PWM_VT8500
> > tristate "vt8500 PWM support"
> > depends on ARCH_VT8500 || COMPILE_TEST
> > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> > index 6374d3b1d6f3..d43b1e17e8e1 100644
> > --- a/drivers/pwm/Makefile
> > +++ b/drivers/pwm/Makefile
> > @@ -56,4 +56,5 @@ obj-$(CONFIG_PWM_TIECAP) += pwm-tiecap.o
> > obj-$(CONFIG_PWM_TIEHRPWM) += pwm-tiehrpwm.o
> > obj-$(CONFIG_PWM_TWL) += pwm-twl.o
> > obj-$(CONFIG_PWM_TWL_LED) += pwm-twl-led.o
> > +obj-$(CONFIG_PWM_VISCONTI) += pwm-visconti.o
> > obj-$(CONFIG_PWM_VT8500) += pwm-vt8500.o
> > diff --git a/drivers/pwm/pwm-visconti.c b/drivers/pwm/pwm-visconti.c
> > new file mode 100644
> > index 000000000000..ff4a5f5b0009
> > --- /dev/null
> > +++ b/drivers/pwm/pwm-visconti.c
> > @@ -0,0 +1,193 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Toshiba Visconti pulse-width-modulation controller driver
> > + *
> > + * Copyright (c) 2020 TOSHIBA CORPORATION
> > + * Copyright (c) 2020 Toshiba Electronic Devices & Storage Corporation
> > + *
> > + * Authors: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@xxxxxxxxxxxxx>
> > + *
> > + */
> > +
> > +#include <linux/err.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> > +#include <linux/of_device.h>
> > +#include <linux/pwm.h>
> > +#include <linux/platform_device.h>
>
> Should be sorted alphabetically.
>
I forgot it, I will fix.
> > +
> > +#define PIPGM_PCSR(ch) (0x400 + 4 * (ch))
> > +#define PIPGM_PDUT(ch) (0x420 + 4 * (ch))
> > +#define PIPGM_PWMC(ch) (0x440 + 4 * (ch))
> > +
> > +#define PIPGM_PWMC_PWMACT BIT(5)
> > +#define PIPGM_PWMC_CLK_MASK GENMASK(1, 0)
> > +#define PIPGM_PWMC_POLARITY_MASK GENMASK(5, 5)
> > +
> > +struct visconti_pwm_chip {
> > + struct pwm_chip chip;
> > + void __iomem *base;
> > +};
> > +
> > +#define to_visconti_chip(chip) \
> > + container_of(chip, struct visconti_pwm_chip, chip)
>
> I prefer these to be static inline functions because that tends to give
> better error messages than macros. Also, that's what's primarily used in
> the PWM drivers, even if there are a couple of outliers.
>
> I'll go fix those up.
I see. I will change to use static inline functions..
>
> > +
> > +static int visconti_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> > + const struct pwm_state *state)
> > +{
> > + struct visconti_pwm_chip *priv = to_visconti_chip(chip);
> > + u32 period, duty_cycle, pwmc0;
> > +
> > + dev_dbg(chip->dev, "%s: ch = %d en = %d p = 0x%llx d = 0x%llx\n", __func__,
> > + pwm->hwpwm, state->enabled, state->period, state->duty_cycle);
>
> Don't the trace points work for you?
Yes, we can get this information by using the trace function. I will
drop this.
>
> > +
> > + /*
> > + * pwmc is a 2-bit divider for the input clock running at 1 MHz.
> > + * When the settings of the PWM are modified, the new values are shadowed in hardware until
> > + * the period register (PCSR) is written and the currently running period is completed. This
> > + * way the hardware switches atomically from the old setting to the new.
> > + * Also, disabling the hardware completes the currently running period and keeps the output
> > + * at low level at all times.
> > + */
> > + if (!state->enabled) {
> > + writel(0, priv->base + PIPGM_PCSR(pwm->hwpwm));
> > + return 0;
> > + }
> > +
> > + /*
> > + * The biggest period the hardware can provide is
> > + * (0xffff << 3) * 1000 ns
> > + * This value fits easily in an u32, so simplify the maths by
> > + * capping the values to 32 bit integers.
> > + */
> > + if (state->period > (0xffff << 3) * 1000)
> > + period = (0xffff << 3) * 1000;
> > + else
> > + period = state->period;
> > +
> > + if (state->duty_cycle > period)
> > + duty_cycle = period;
> > + else
> > + duty_cycle = state->duty_cycle;
> > +
> > + /*
> > + * The input clock runs fixed at 1 MHz, so we have only
> > + * microsecond resolution and so can divide by
> > + * NSEC_PER_SEC / CLKFREQ = 1000 without loosing precision.
> > + */
> > + period /= 1000;
> > + duty_cycle /= 1000;
> > +
> > + if (!period)
> > + /* period too small */
> > + return -ERANGE;
>
> Maybe braces around this so the two-line "block" doesn't look wrong,
> even if it actually isn't. Or perhaps put the comment above the check
> for the same effect.
I see, it's readability.
>
> Quite frankly, I'd just drop the comment because the code itself is
> clear and the comment doesn't add anything.
OK, I will drop this comment.
>
> > +
> > + /*
> > + * PWMC controls a divider that divides the input clk by a
> > + * power of two between 1 and 8. As a smaller divider yields
> > + * higher precision, pick the smallest possible one.
> > + */
> > + if (period > 0xffff) {
> > + pwmc0 = ilog2(period >> 16);
> > + BUG_ON(pwmc0 > 3);
> > + } else
> > + pwmc0 = 0;
> > +
> > + period >>= pwmc0;
> > + duty_cycle >>= pwmc0;
> > +
> > + if (state->polarity == PWM_POLARITY_INVERSED)
> > + pwmc0 |= PIPGM_PWMC_PWMACT;
> > + writel(pwmc0, priv->base + PIPGM_PWMC(pwm->hwpwm));
> > + writel(duty_cycle, priv->base + PIPGM_PDUT(pwm->hwpwm));
> > + writel(period, priv->base + PIPGM_PCSR(pwm->hwpwm));
> > +
> > + return 0;
> > +}
> > +
> > +static void visconti_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> > + struct pwm_state *state)
> > +{
> > + struct visconti_pwm_chip *priv = to_visconti_chip(chip);
> > + u32 period, duty, pwmc0, pwmc0_clk;
> > +
> > + period = readl(priv->base + PIPGM_PCSR(pwm->hwpwm));
> > + if (period)
> > + state->enabled = true;
> > + else
> > + state->enabled = false;
> > +
> > + duty = readl(priv->base + PIPGM_PDUT(pwm->hwpwm));
> > + pwmc0 = readl(priv->base + PIPGM_PWMC(pwm->hwpwm));
> > + pwmc0_clk = pwmc0 & PIPGM_PWMC_CLK_MASK;
> > +
> > + state->period = (period << pwmc0_clk) * NSEC_PER_USEC;
> > + state->duty_cycle = (duty << pwmc0_clk) * NSEC_PER_USEC;
> > + if (pwmc0 & PIPGM_PWMC_POLARITY_MASK)
> > + state->polarity = PWM_POLARITY_INVERSED;
> > + else
> > + state->polarity = PWM_POLARITY_NORMAL;
> > +}
> > +
> > +static const struct pwm_ops visconti_pwm_ops = {
> > + .apply = visconti_pwm_apply,
> > + .get_state = visconti_pwm_get_state,
> > + .owner = THIS_MODULE,
> > +};
> > +
> > +static int visconti_pwm_probe(struct platform_device *pdev)
> > +{
> > + struct device *dev = &pdev->dev;
> > + struct visconti_pwm_chip *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);
> > +
> > + platform_set_drvdata(pdev, priv);
> > +
> > + priv->chip.dev = dev;
> > + priv->chip.ops = &visconti_pwm_ops;
> > + priv->chip.base = -1;
>
> There's no need for this anymore. The current PWM tree will always
> assume base = -1.
I see. I will drop this.
>
> > + priv->chip.npwm = 4;
> > +
> > + ret = pwmchip_add(&priv->chip);
> > + if (ret < 0)
> > + return dev_err_probe(&pdev->dev, ret, "Cannot register visconti PWM\n");
> > +
> > + dev_dbg(&pdev->dev, "visconti PWM registered\n");
>
> Maybe not the best use of a debug message. There are better ways to
> check if a device has successfully bound to a driver than relying on
> debug messages.
I will drop this line. it says there are better way to check, but what is it?
>
> > +
> > + return 0;
> > +}
> > +
> > +static int visconti_pwm_remove(struct platform_device *pdev)
> > +{
> > + struct visconti_pwm_chip *priv = platform_get_drvdata(pdev);
> > +
> > + return pwmchip_remove(&priv->chip);
>
> I think Uwe would prefer this to be done separately because he's working
> towards removing the return value from pwmchip_remove() and if we start
> ignoring it in new drivers that will make life easier going forward.
>
> So this should just be:
>
> pwmchip_remove(&priv->chip);
>
> return 0;
I understand your suggestion.
However, it looks like the pwmchip_remove() hasn't been updated yet.
I will wait for the update of pwmchip_remove.
>
> Thierry
Best regards,
Nobuhiro
