linux-kernel - Re: [PATCH v2 03/10] pwm: imx: Rewrite imx_pwm_*_v1 code to facilitate switch to atomic pwm operation

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Message-ID: <20161102081852.7d1f2b70@ipc1.ka-ro>
Date:   Wed, 2 Nov 2016 08:18:52 +0100
From:   Lothar Waßmann <LW@...O-electronics.de>
To:     Sascha Hauer <s.hauer@...gutronix.de>
Cc:     Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Lukasz Majewski <l.majewski@...ess.pl>,
        linux-pwm@...r.kernel.org,
        Bhuvanchandra DV <bhuvanchandra.dv@...adex.com>,
        linux-kernel@...r.kernel.org, Stefan Agner <stefan@...er.ch>,
        Thierry Reding <thierry.reding@...il.com>,
        kernel@...gutronix.de, Fabio Estevam <fabio.estevam@....com>,
        Fabio Estevam <festevam@...il.com>,
        Philipp Zabel <pza@...gutronix.de>
Subject: Re: [PATCH v2 03/10] pwm: imx: Rewrite imx_pwm_*_v1 code to
 facilitate switch to atomic pwm operation

Hi,

On Mon, 31 Oct 2016 06:59:04 +0100 Sascha Hauer wrote:
> As said, even the commit 7b27c160c68 introducing the register clk did not
> enable the clock consistently for all register accesses. Maybe it's best
> to include the following patch so that we can find a clear culprit and
> do not bury the ipg clock changes in larger patches.
> 
> Sascha
> 
> -----------------------------8<-----------------------------------
> 
> From 30b77e83269a58c2cb5ce6de8be647e027030d34 Mon Sep 17 00:00:00 2001
> From: Sascha Hauer <s.hauer@...gutronix.de>
> Date: Mon, 31 Oct 2016 06:45:33 +0100
> Subject: [PATCH] pwm: imx: remove ipg clock
> 
> The use of the ipg clock was introduced with commit 7b27c160c6. 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.
> 
> Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> Cc: Philipp Zabel <p.zabel@...gutronix.de>
> ---
>  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;
>
If the IPG clock is not needed by the driver it should be removed from
DT as well.



Lothar Waßmann