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SubjectRe: [PATCH 1/6] pwm: imx: Rewrite imx_pwm_*_v1 code to facilitate switch to atomic pwm operation
On Sun, Oct 23, 2016 at 11:45:41PM +0200, Lukasz Majewski wrote:
> The code has been rewritten to remove "generic" calls to
> imx_pwm_{enable|disable|config}.
>
> Such approach would facilitate switch to atomic PWM (a.k.a ->apply())
> implementation.
>
> Suggested-by: Stefan Agner <stefan@agner.ch>
> Suggested-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
> ---
> drivers/pwm/pwm-imx.c | 46 ++++++++++++++++++++++++++++++++++------------
> 1 file changed, 34 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
> index c37d223..83e43d5 100644
> --- a/drivers/pwm/pwm-imx.c
> +++ b/drivers/pwm/pwm-imx.c
> @@ -66,8 +66,6 @@ struct imx_chip {
> static int imx_pwm_config_v1(struct pwm_chip *chip,
> struct pwm_device *pwm, int duty_ns, int period_ns)
> {
> - struct imx_chip *imx = to_imx_chip(chip);
> -
> /*
> * The PWM subsystem allows for exact frequencies. However,
> * I cannot connect a scope on my device to the PWM line and
> @@ -85,26 +83,52 @@ static int imx_pwm_config_v1(struct pwm_chip *chip,
> * both the prescaler (/1 .. /128) and then by CLKSEL
> * (/2 .. /16).
> */
> + struct imx_chip *imx = to_imx_chip(chip);
> u32 max = readl(imx->mmio_base + MX1_PWMP);
> u32 p = max * duty_ns / period_ns;
> + int ret;
> +
> + ret = clk_prepare_enable(imx->clk_ipg);
> + if (ret)
> + return ret;
> +
> writel(max - p, imx->mmio_base + MX1_PWMS);
>
> + clk_disable_unprepare(imx->clk_ipg);
> +
> return 0;
> }
>
> -static void imx_pwm_set_enable_v1(struct pwm_chip *chip, bool enable)
> +static int imx_pwm_enable_v1(struct pwm_chip *chip, struct pwm_device *pwm)
> {
> struct imx_chip *imx = to_imx_chip(chip);
> + int ret;
> u32 val;
>
> + ret = clk_prepare_enable(imx->clk_ipg);
> + if (ret)
> + return ret;
> +
> val = readl(imx->mmio_base + MX1_PWMC);
> + val |= MX1_PWMC_EN;
> + writel(val, imx->mmio_base + MX1_PWMC);
>
> - if (enable)
> - val |= MX1_PWMC_EN;
> - else
> - val &= ~MX1_PWMC_EN;
> + clk_disable_unprepare(imx->clk_per);

This looks wrong. You start by enabling clk_ipg which is needed for
register access, but then end with disabling clk_per which is needed for
driving the actual PWM output. This function should probably enable
clk_per on entry and enable clk_ipg while accessing registers.

Sascha

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