Re: [PATCH v2 1/3] pwm: jz4740: Use clocks from TCU driver

Uwe Kleine-König
2019-11-17T20:20:37Z

On Sat, Nov 16, 2019 at 06:36:11PM +0100, Paul Cercueil wrote:
> The ingenic-timer "TCU" driver provides us with clocks, that can be
> (un)gated, reparented or reclocked from devicetree, instead of having
> these settings hardcoded in this driver.
>
> While this driver is devicetree-compatible, it is never (as of now)
> probed from devicetree, so this change does not introduce a ABI problem
> with current devicetree files.
>
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> Tested-by: Mathieu Malaterre <malat@debian.org>
> Tested-by: Artur Rojek <contact@artur-rojek.eu>
> ---
>
> Notes:
> v2: This patch is now before the patch introducing regmap, so the code
> has changed a bit.
>
> drivers/pwm/Kconfig | 1 +
> drivers/pwm/pwm-jz4740.c | 45 ++++++++++++++++++++++++++++------------
> 2 files changed, 33 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index e3a2518503ed..e998e5cb01b0 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -225,6 +225,7 @@ config PWM_IMX_TPM
> config PWM_JZ4740
> tristate "Ingenic JZ47xx PWM support"
> depends on MACH_INGENIC
> + depends on COMMON_CLK
> help
> Generic PWM framework driver for Ingenic JZ47xx based
> machines.
> diff --git a/drivers/pwm/pwm-jz4740.c b/drivers/pwm/pwm-jz4740.c
> index 9d78cc21cb12..fd83644f9323 100644
> --- a/drivers/pwm/pwm-jz4740.c
> +++ b/drivers/pwm/pwm-jz4740.c
> @@ -24,7 +24,6 @@
>
> struct jz4740_pwm_chip {
> struct pwm_chip chip;
> - struct clk *clk;

What is the motivation to go away from this approach to store the clock?

> };
>
> static inline struct jz4740_pwm_chip *to_jz4740(struct pwm_chip *chip)
> @@ -34,6 +33,11 @@ static inline struct jz4740_pwm_chip *to_jz4740(struct pwm_chip *chip)
>
> static int jz4740_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
> {
> + struct jz4740_pwm_chip *jz = to_jz4740(chip);
> + struct clk *clk;
> + char clk_name[16];
> + int ret;
> +
> /*
> * Timers 0 and 1 are used for system tasks, so they are unavailable
> * for use as PWMs.
> @@ -41,16 +45,31 @@ static int jz4740_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
> if (pwm->hwpwm < 2)
> return -EBUSY;
>
> - jz4740_timer_start(pwm->hwpwm);
> + snprintf(clk_name, sizeof(clk_name), "timer%u", pwm->hwpwm);
> +
> + clk = clk_get(chip->dev, clk_name);
> + if (IS_ERR(clk))

if (PTR_ERR(clk) != -EPROBE_DEFER)
dev_err(chip->dev, "Failed to get clock: %pe\n", clk);

> + return PTR_ERR(clk);
> +
> + ret = clk_prepare_enable(clk);
> + if (ret) {
> + clk_put(clk);
> + return ret;
> + }
> +
> + pwm_set_chip_data(pwm, clk);
>
> return 0;
> }
>
> static void jz4740_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
> {
> + struct clk *clk = pwm_get_chip_data(pwm);
> +
> jz4740_timer_set_ctrl(pwm->hwpwm, 0);

What is the purpose of this call? I would have expected that all these
would go away when converting to the clk stuff?!

> - jz4740_timer_stop(pwm->hwpwm);
> + clk_disable_unprepare(clk);
> + clk_put(clk);
> }
>
> static int jz4740_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> @@ -91,17 +110,21 @@ static int jz4740_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> const struct pwm_state *state)
> {
> struct jz4740_pwm_chip *jz4740 = to_jz4740(pwm->chip);
> + struct clk *clk = pwm_get_chip_data(pwm),
> + *parent_clk = clk_get_parent(clk);
> + unsigned long rate, period, duty;
> unsigned long long tmp;
> - unsigned long period, duty;
> unsigned int prescaler = 0;
> uint16_t ctrl;
>
> - tmp = (unsigned long long)clk_get_rate(jz4740->clk) * state->period;
> + rate = clk_get_rate(parent_clk);

Why is it the parent's rate that is relevant here?

> + tmp = (unsigned long long)rate * state->period;
> do_div(tmp, 1000000000);
> period = tmp;
>
> while (period > 0xffff && prescaler < 6) {
> period >>= 2;
> + rate >>= 2;
> ++prescaler;
> }
>
> @@ -117,14 +140,14 @@ static int jz4740_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>
> jz4740_pwm_disable(chip, pwm);
>
> + clk_set_rate(clk, rate);

This function's return code must be checked.

> jz4740_timer_set_count(pwm->hwpwm, 0);
> jz4740_timer_set_duty(pwm->hwpwm, duty);
> jz4740_timer_set_period(pwm->hwpwm, period);
>
> - ctrl = JZ_TIMER_CTRL_PRESCALER(prescaler) | JZ_TIMER_CTRL_SRC_EXT |
> - JZ_TIMER_CTRL_PWM_ABBRUPT_SHUTDOWN;
> -
> - jz4740_timer_set_ctrl(pwm->hwpwm, ctrl);
> + ctrl = jz4740_timer_get_ctrl(pwm->hwpwm);
> + ctrl |= JZ_TIMER_CTRL_PWM_ABBRUPT_SHUTDOWN;
>
> switch (state->polarity) {
> case PWM_POLARITY_NORMAL:

Best regards
Uwe

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