linux-kernel - Re: [PATCH] drm/ast: Fix soft lockup

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Date: Wed, 27 Mar 2024 09:53:45 +0100
From: Jocelyn Falempe <jfalempe@...hat.com>
To: Jammy Huang <orbit.huang@...il.com>, tzimmermann@...e.de,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org, airlied@...hat.com,
 airlied@...il.com, daniel@...ll.ch
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 Jammy Huang <jammy_huang@...eedtech.com>, stable@...r.kernel.org
Subject: Re: [PATCH] drm/ast: Fix soft lockup

Hi,

Thanks for your patch.
I'm wondering how you can trigger this infinite loop ?

Also this looks like a simple fix, that can be easily backported, so I'm 
adding stable in Cc.

If Thomas has no objections, I can push it to drm-misc-fixes.

Reviewed-by: Jocelyn Falempe <jfalempe@...hat.com>

-- 

Jocelyn

On 25/03/2024 04:35, Jammy Huang wrote:
> Avoid infinite-loop in ast_dp_set_on_off().
> 
> Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
> ---
>   drivers/gpu/drm/ast/ast_dp.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c
> index ebb6d8ebd44e..1e9259416980 100644
> --- a/drivers/gpu/drm/ast/ast_dp.c
> +++ b/drivers/gpu/drm/ast/ast_dp.c
> @@ -180,6 +180,7 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on)
>   {
>   	struct ast_device *ast = to_ast_device(dev);
>   	u8 video_on_off = on;
> +	u32 i = 0;
>   
>   	// Video On/Off
>   	ast_set_index_reg_mask(ast, AST_IO_VGACRI, 0xE3, (u8) ~AST_DP_VIDEO_ENABLE, on);
> @@ -192,6 +193,8 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on)
>   						ASTDP_MIRROR_VIDEO_ENABLE) != video_on_off) {
>   			// wait 1 ms
>   			mdelay(1);
> +			if (++i > 200)
> +				break;
>   		}
>   	}
>   }
> 
> base-commit: b0546776ad3f332e215cebc0b063ba4351971cca