linux-kernel - Re: [PATCH v2] gpu: cdns-mhdp8546: fix call balance of mhdp->clk handling routines

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Message-ID: <nhklokfut4vz7ijfxdzy64qngzmdsk4ji3xq2nj2c6uhrvonru@tn3y5b4madyx>
Date: Fri, 14 Feb 2025 05:06:21 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Vitalii Mordan <mordan@...ras.ru>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Sui Jingfeng <sui.jingfeng@...ux.dev>, Aleksandr Mishin <amishin@...rgos.ru>, 
	Al Viro <viro@...iv.linux.org.uk>, Tomi Valkeinen <tomi.valkeinen@...com>, 
	Jyri Sarha <jsarha@...com>, Quentin Schulz <quentin.schulz@...e-electrons.com>, 
	Swapnil Jakhade <sjakhade@...ence.com>, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	Fedor Pchelkin <pchelkin@...ras.ru>, Alexey Khoroshilov <khoroshilov@...ras.ru>, 
	Vadim Mutilin <mutilin@...ras.ru>, lvc-project@...uxtesting.org
Subject: Re: [PATCH v2] gpu: cdns-mhdp8546: fix call balance of mhdp->clk
 handling routines

On Thu, Feb 13, 2025 at 02:28:01PM +0300, Vitalii Mordan wrote:
> If the clock mhdp->clk was not enabled in cdns_mhdp_probe(), it should not
> be disabled in any path.
> 
> Use the devm_clk_get_enabled() helper function to ensure proper call
> balance for mhdp->clk.
> 
> Found by Linux Verification Center (linuxtesting.org) with Klever.
> 
> Fixes: fb43aa0acdfd ("drm: bridge: Add support for Cadence MHDP8546 DPI/DP bridge")

Please describe, what is the actual issue that is being fixed. In other
words, which path leads to unbalanced enable or disable call. Otherwise
it seems to be a valid patch, not qualified as a fix.

> Signed-off-by: Vitalii Mordan <mordan@...ras.ru>
> ---
> v2: Use devm_clk_get_enabled() helper function, as per Dmitry Baryshkov's
> request.
> 
>  drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> index d081850e3c03..d4e4f484cbe5 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> @@ -2463,9 +2463,9 @@ static int cdns_mhdp_probe(struct platform_device *pdev)
>  	if (!mhdp)
>  		return -ENOMEM;
>  
> -	clk = devm_clk_get(dev, NULL);
> +	clk = devm_clk_get_enabled(dev, NULL);
>  	if (IS_ERR(clk)) {
> -		dev_err(dev, "couldn't get clk: %ld\n", PTR_ERR(clk));
> +		dev_err(dev, "couldn't get and enable clk: %ld\n", PTR_ERR(clk));
>  		return PTR_ERR(clk);
>  	}
>  
> @@ -2504,14 +2504,12 @@ static int cdns_mhdp_probe(struct platform_device *pdev)
>  
>  	mhdp->info = of_device_get_match_data(dev);
>  
> -	clk_prepare_enable(clk);
> -
>  	pm_runtime_enable(dev);
>  	ret = pm_runtime_resume_and_get(dev);
>  	if (ret < 0) {
>  		dev_err(dev, "pm_runtime_resume_and_get failed\n");
>  		pm_runtime_disable(dev);
> -		goto clk_disable;
> +		return ret;
>  	}
>  
>  	if (mhdp->info && mhdp->info->ops && mhdp->info->ops->init) {
> @@ -2590,8 +2588,6 @@ static int cdns_mhdp_probe(struct platform_device *pdev)
>  runtime_put:
>  	pm_runtime_put_sync(dev);
>  	pm_runtime_disable(dev);
> -clk_disable:
> -	clk_disable_unprepare(mhdp->clk);
>  
>  	return ret;
>  }
> @@ -2632,8 +2628,6 @@ static void cdns_mhdp_remove(struct platform_device *pdev)
>  	cancel_work_sync(&mhdp->modeset_retry_work);
>  	flush_work(&mhdp->hpd_work);
>  	/* Ignoring mhdp->hdcp.check_work and mhdp->hdcp.prop_work here. */
> -
> -	clk_disable_unprepare(mhdp->clk);
>  }
>  
>  static const struct of_device_id mhdp_ids[] = {
> -- 
> 2.25.1
> 

-- 
With best wishes
Dmitry