Re: [PATCH v3 RESEND 02/11] pwm: imx: remove ipg clock
From: Stefan Agner
Date: Tue Dec 27 2016 - 02:33:28 EST
On 2016-12-26 23:55, Lukasz Majewski wrote:
> From: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
>
> The use of the ipg clock was introduced with commit 7b27c160c681
> ("pwm: i.MX: fix clock lookup").
> In the commit message it was claimed that the ipg clock is enabled for
> register accesses. This is true for the ->config() callback, but not
> for the ->set_enable() callback. Given that the ipg clock is not
> consistently enabled for all register accesses we can assume that either
> it is not required at all or that the current code does not work.
> Remove the ipg clock code for now so that it's no longer in the way of
> refactoring the driver.
Hi Lukasz,
Has my concern addressed in any way with this resend?
https://lkml.org/lkml/2016/11/22/729
Breaking hardware is usually not an option :-)
I checked the i.MX 7 reference manual again, and in this case the
peripheral access clock is a clock line named "ipg_clk_s" (Table 12-20),
with a clock root "PWM1_CLK_ROOT" (Table 5-12). In i.MX 7 all clocks are
behind a single gate, so in fact it does not matter which clock we take.
Given that others have peripheral access behind the "pwm" gate, I guess
we should take the "pwm" gate...
--
Stefan
>
> Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> Cc: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> ---
> [commit message text refactored by Lukasz Majewski <l.majewski@xxxxxxxxx>]
> ---
> Changes for v3:
> - New patch
> ---
> drivers/pwm/pwm-imx.c | 19 +------------------
> 1 file changed, 1 insertion(+), 18 deletions(-)
>
> diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
> index d600fd5..70609ef2 100644
> --- a/drivers/pwm/pwm-imx.c
> +++ b/drivers/pwm/pwm-imx.c
> @@ -49,7 +49,6 @@
>
> struct imx_chip {
> struct clk *clk_per;
> - struct clk *clk_ipg;
>
> void __iomem *mmio_base;
>
> @@ -204,17 +203,8 @@ static int imx_pwm_config(struct pwm_chip *chip,
> struct pwm_device *pwm, int duty_ns, int period_ns)
> {
> struct imx_chip *imx = to_imx_chip(chip);
> - int ret;
> -
> - ret = clk_prepare_enable(imx->clk_ipg);
> - if (ret)
> - return ret;
>
> - ret = imx->config(chip, pwm, duty_ns, period_ns);
> -
> - clk_disable_unprepare(imx->clk_ipg);
> -
> - return ret;
> + return imx->config(chip, pwm, duty_ns, period_ns);
> }
>
> static int imx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> @@ -293,13 +283,6 @@ static int imx_pwm_probe(struct platform_device *pdev)
> return PTR_ERR(imx->clk_per);
> }
>
> - imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
> - if (IS_ERR(imx->clk_ipg)) {
> - dev_err(&pdev->dev, "getting ipg clock failed with %ld\n",
> - PTR_ERR(imx->clk_ipg));
> - return PTR_ERR(imx->clk_ipg);
> - }
> -
> imx->chip.ops = &imx_pwm_ops;
> imx->chip.dev = &pdev->dev;
> imx->chip.base = -1;