linux-kernel - Re: [PATCH] drm/komeda: Remove unnecessary NULL check before clk_prepare

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Message-ID: <Z9Lm6nSPphPfupEB@e110455-lin.cambridge.arm.com>
Date: Thu, 13 Mar 2025 14:08:42 +0000
From: Liviu Dudau <liviu.dudau@....com>
To: Chen Ni <nichen@...as.ac.cn>
Cc: maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
	tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/komeda: Remove unnecessary NULL check before
 clk_prepare_enable()

On Thu, Mar 13, 2025 at 04:29:07PM +0800, Chen Ni wrote:
> clk_prepare_enable() already checked NULL clock parameter.
> Remove unneeded NULL check for clk here.

You're not saving anything here. If mdev->aclk is NULL you still end up
calling clk_prepare() and clk_enable() even if they return zero immediately.
And if you don't like the check for mdev->aclk not being NULL, you should
also move the clk_disable_unprepare() call outside the if() {...} block.

Best regards,
Liviu

> 
> Signed-off-by: Chen Ni <nichen@...as.ac.cn>
> ---
>  drivers/gpu/drm/arm/display/komeda/komeda_dev.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> index 5ba62e637a61..2b59830f0572 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> @@ -282,8 +282,7 @@ void komeda_dev_destroy(struct komeda_dev *mdev)
>  
>  	debugfs_remove_recursive(mdev->debugfs_root);
>  
> -	if (mdev->aclk)
> -		clk_prepare_enable(mdev->aclk);
> +	clk_prepare_enable(mdev->aclk);
>  
>  	for (i = 0; i < mdev->n_pipelines; i++) {
>  		komeda_pipeline_destroy(mdev, mdev->pipelines[i]);
> -- 
> 2.25.1
> 

-- 
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