linux-kernel - Re: [PATCH] drm/amd/display: replace use of msleep(<20) with usleep

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Message-ID: <476c5bb9-79c5-40b7-bba8-b52fb244e90e@linuxfoundation.org>
Date: Fri, 28 Mar 2025 16:46:00 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: James Flowers <bold.zone2373@...tmail.com>, harry.wentland@....com,
 sunpeng.li@....com, siqueira@...lia.com, alexander.deucher@....com,
 christian.koenig@....com, airlied@...il.com, simona@...ll.ch,
 aurabindo.pillai@....com, alex.hung@....com
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel-mentees@...ts.linux.dev, linux-kernel@...r.kernel.org,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] drm/amd/display: replace use of msleep(<20) with
 usleep_range for better accuracy

On 3/26/25 01:00, James Flowers wrote:
> msleep < 20ms will often sleep for ~20ms (according to Documentation/timers/timers-howto.rst).

Can you elaborate and explain why this change is necessary?

> 
> Signed-off-by: James Flowers <bold.zone2373@...tmail.com>
> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> index 2cd35392e2da..2d225735602b 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> @@ -682,7 +682,7 @@ static bool execute_synaptics_rc_command(struct drm_dp_aux *aux,
>   		if (rc_cmd == cmd)
>   			// active is 0
>   			break;
> -		msleep(10);
> +		usleep_range(10000, 10200);
>   	}
>   
>   	// read rc result

thanks,
-- Shuah