linux-kernel - Re: [PATCH v4 1/2] pwm: mtk_disp: fix pwm clocks not poweroff when disable pwm

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Date:   Mon, 20 Jan 2020 15:31:34 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Jitao Shi <jitao.shi@...iatek.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-pwm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, CK Hu <ck.hu@...iatek.com>,
        linux-mediatek@...ts.infradead.org, sj.huang@...iatek.com
Subject: Re: [PATCH v4 1/2] pwm: mtk_disp: fix pwm clocks not poweroff when
 disable pwm

Hello,

I fully agree to what Thierry said about the commit log.

One more comment:

On Tue, Dec 17, 2019 at 12:02:36PM +0800, Jitao Shi wrote:
> @@ -194,14 +194,6 @@ static int mtk_disp_pwm_probe(struct platform_device *pdev)
>  	if (IS_ERR(mdp->clk_mm))
>  		return PTR_ERR(mdp->clk_mm);
>  
> -	ret = clk_prepare(mdp->clk_main);
> -	if (ret < 0)
> -		return ret;
> -
> -	ret = clk_prepare(mdp->clk_mm);
> -	if (ret < 0)
> -		goto disable_clk_main;
> -
>  	mdp->chip.dev = &pdev->dev;
>  	mdp->chip.ops = &mtk_disp_pwm_ops;
>  	mdp->chip.base = -1;

After this there is:

	if (!mdp->data->has_commit) {
		mtk_disp_pwm_update_bits(mdp, mdp->data->bls_debug, ...);
		...
	}

So I wonder if dropping the clk_enables above is safe if there are some
register accesses later on.

Side note: The driver you're touching here is still using the legacy
API. Would be great to convert it to .apply() instead.

Best regards
Uwe

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