linux-kernel - Re: [PATCH 5/7] pwm: dwc: add timer clock

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Date:   Wed, 13 Jul 2022 08:10:24 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Ben Dooks <ben.dooks@...ive.com>
Cc:     linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Greentime Hu <greentime.hu@...ive.com>,
        Jude Onyenegecha <jude.onyenegecha@...ive.com>,
        Sudip Mukherjee <sudip.mukherjee@...ive.com>,
        William Salmon <william.salmon@...ive.com>,
        Adnan Chowdhury <adnan.chowdhury@...ive.com>
Subject: Re: [PATCH 5/7] pwm: dwc: add timer clock

On Tue, Jul 12, 2022 at 11:01:11AM +0100, Ben Dooks wrote:
> Add a configurable clock base rate for the pwm as when
> being built for non-PCI the block may be sourced from
> an internal clock.
> 
> Signed-off-by: Ben Dooks <ben.dooks@...ive.com>
> ---
>  drivers/pwm/pwm-dwc.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/pwm/pwm-dwc.c b/drivers/pwm/pwm-dwc.c
> index 235cb730c888..aa0486b89bdd 100644
> --- a/drivers/pwm/pwm-dwc.c
> +++ b/drivers/pwm/pwm-dwc.c
> @@ -18,6 +18,7 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/pci.h>
> +#include <linux/clk.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/pwm.h>
> @@ -35,7 +36,12 @@
>  #define DWC_TIMERS_COMP_VERSION	0xac
>  
>  #define DWC_TIMERS_TOTAL	8
> +
> +#ifndef CONFIG_OF
>  #define DWC_CLK_PERIOD_NS	10
> +#else
> +#define DWC_CLK_PERIOD_NS	dwc->clk_ns
> +#endif

Hmm, that looks wrong. If you have CONFIG_OF but use the pci device ...

IMHO it would help readability if you used ifdef. When there is an #else
branch anyhow, there is no reason to use the negative variant.

>  /* Timer Control Register */
>  #define DWC_TIM_CTRL_EN		BIT(0)
> @@ -54,6 +60,8 @@ struct dwc_pwm_ctx {
>  struct dwc_pwm {
>  	struct pwm_chip chip;
>  	void __iomem *base;
> +	struct clk *clk;
> +	unsigned int clk_ns;
>  	struct dwc_pwm_ctx ctx[DWC_TIMERS_TOTAL];
>  };
>  #define to_dwc_pwm(p)	(container_of((p), struct dwc_pwm, chip))
> @@ -336,6 +344,14 @@ static int dwc_pwm_plat_probe(struct platform_device *pdev)
>  		return dev_err_probe(dev, PTR_ERR(dwc->base),
>  				     "failed to map IO\n");
>  
> +	dwc->clk = devm_clk_get(dev, "timer");
> +	if (IS_ERR(dwc->clk))
> +		return dev_err_probe(dev, PTR_ERR(dwc->clk),
> +				     "failed to get timer clock\n");
> +
> +	clk_prepare_enable(dwc->clk);
> +	dwc->clk_ns = 1000000000 /clk_get_rate(dwc->clk);
> +
>  	ret = pwmchip_add(&dwc->chip);
>  	if (ret)
>  		return ret;

Here you're missing clk_disable_unprepare(). (Alternatively use
devm_clk_get_enabled().)

> @@ -347,6 +363,7 @@ static int dwc_pwm_plat_remove(struct platform_device *pdev)
>  {
>  	struct dwc_pwm *dwc = platform_get_drvdata(pdev);
>  
> +	clk_disable_unprepare(dwc->clk);
>  	pwmchip_remove(&dwc->chip);

The order is wrong here. You must only stop the clk when the pwmchip is
removed. Until that the PWM is supposed to stay functional.

>  	return 0;
>  }

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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