linux-kernel - Re: [PATCH v2] drm/msm: Avoid rounding up to one jiffy

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Message-ID: <4f0ca15e-770e-4192-b390-a3039c68e4b4@quicinc.com>
Date: Thu, 16 Jan 2025 00:44:48 +0530
From: Akhil P Oommen <quic_akhilpo@...cinc.com>
To: Rob Clark <robdclark@...il.com>, <dri-devel@...ts.freedesktop.org>
CC: <freedreno@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        "Rob
 Clark" <robdclark@...omium.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie
	<airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        open list
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/msm: Avoid rounding up to one jiffy

On 1/13/2025 9:18 PM, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
> 
> If userspace is trying to achieve a timeout of zero, let 'em have it.
> Only round up if the timeout is greater than zero.
> 
> Fixes: 4969bccd5f4e ("drm/msm: Avoid rounding down to zero jiffies")
> Signed-off-by: Rob Clark <robdclark@...omium.org>

Reviewed-by: Akhil P Oommen <quic_akhilpo@...cinc.com>

-Akhil

> ---
>  drivers/gpu/drm/msm/msm_drv.h | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index fee31680a6d5..a65077855201 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -537,15 +537,12 @@ static inline int align_pitch(int width, int bpp)
>  static inline unsigned long timeout_to_jiffies(const ktime_t *timeout)
>  {
>  	ktime_t now = ktime_get();
> -	s64 remaining_jiffies;
>  
> -	if (ktime_compare(*timeout, now) < 0) {
> -		remaining_jiffies = 0;
> -	} else {
> -		ktime_t rem = ktime_sub(*timeout, now);
> -		remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ);
> -	}
> +	if (ktime_compare(*timeout, now) <= 0)
> +		return 0;
>  
> +	ktime_t rem = ktime_sub(*timeout, now);
> +	s64 remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ);
>  	return clamp(remaining_jiffies, 1LL, (s64)INT_MAX);
>  }
>