linux-kernel - Re: [PATCH] media: rzg2l-cru: Replace usleep

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Message-ID: <20251203023552.GM8219@pendragon.ideasonboard.com>
Date: Wed, 3 Dec 2025 11:35:52 +0900
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Tommaso Merciai <tommaso.merciai.xr@...renesas.com>
Cc: tomm.merciai@...il.com, linux-renesas-soc@...r.kernel.org,
	biju.das.jz@...renesas.com,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Hans Verkuil <hverkuil+cisco@...nel.org>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
	Daniel Scally <dan.scally+renesas@...asonboard.com>,
	Jacopo Mondi <jacopo.mondi@...asonboard.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	Khai Nguyen <khai.nguyen.wx@...esas.com>,
	Hao Bui <hao.bui.yg@...esas.com>
Subject: Re: [PATCH] media: rzg2l-cru: Replace usleep_range with udelay

Hi Tommaso,

Thank you for the patch.

On Tue, Dec 02, 2025 at 05:08:41PM +0100, Tommaso Merciai wrote:
> `usleep_range()` should not be used in atomic contexts like between
> spin_lock_irqsave()/spin_lock_irqrestore() pair inside function
> rzg2l_cru_stop_image_processing(). That may cause scheduling while
> atomic bug.
> 
> Signed-off-by: Khai Nguyen <khai.nguyen.wx@...esas.com>
> Signed-off-by: Hao Bui <hao.bui.yg@...esas.com>
> Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@...renesas.com>
> ---
>  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> index 162e2ace6931..1355bfd186d4 100644
> --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> @@ -369,7 +369,7 @@ void rzg2l_cru_stop_image_processing(struct rzg2l_cru_dev *cru)
>  		if (cru->info->fifo_empty(cru))
>  			break;
>  
> -		usleep_range(10, 20);
> +		udelay(10);

There's an instance of msleep() earlier in this function, surrounded by
spin_unlock_irqrestore() and spin_lock_irqsave(). I wondered if we
should do the same here, but that lead to a second question: why does
the driver need to cover the whole stop procedure with a spinlock in the
first place ?

>  	}
>  
>  	/* Notify that FIFO is not empty here */
> @@ -385,7 +385,7 @@ void rzg2l_cru_stop_image_processing(struct rzg2l_cru_dev *cru)
>  			AMnAXISTPACK_AXI_STOP_ACK)
>  			break;
>  
> -		usleep_range(10, 20);
> +		udelay(10);
>  	}
>  
>  	/* Notify that AXI bus can not stop here */

-- 
Regards,

Laurent Pinchart