linux-kernel - Re: [PATCH] drm/vkms: fix warning in vkms_get_vblank

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Message-ID: <20200827013549.GA7953@realwakka>
Date:   Thu, 27 Aug 2020 01:35:49 +0000
From:   Sidong Yang <realwakka@...il.com>
To:     Melissa Wen <melissa.srw@...il.com>
Cc:     Daniel Vetter <daniel@...ll.ch>,
        Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>,
        Haneen Mohammed <hamohammed.sa@...il.com>,
        Emil Velikov <emil.l.velikov@...il.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/vkms: fix warning in vkms_get_vblank_timestamp

On Wed, Aug 26, 2020 at 05:49:54PM -0300, Melissa Wen wrote:

Hi Melissa!
Thanks for review.

> Hi Sidong,
> 
> Thanks for this patch.
> 
> The code looks good to me; however, I see some issues in the patch
> format and commit message. Please, see inline comments.
> 
> On 08/25, Sidong Yang wrote:
> > From: Sidong Yang <realwakka@...il.com>, Haneen Mohammed <hamohammed.sa@...il.com>
> 
> You need to fix the Author name.

Oops. 

> > 
> > When vkms_get_vblank_timestamp() is called very first time without
> > enabling vblank before, vblank time has just intial value and it makes
> > warning message. this patch prevents warning message by setting vblank
> > time to current time.
> 
> I consider *fix* a somewhat strong term to this change. In my opinion,
> it would be better to choose another term in the commit message like
> *avoid* timestamp warning when vblanks aren't enabled.

It's good to me. Next patch need to be more explicit.

> 
> In the body of the commit message, I think interesting to include the
> exactly warning message that this patch addresses. You could also
> describe the initial values that triggers this warning and why this
> approach is reasonable, as VKMS has fake clocks.

Yeah, It will be more comprehensive patch if there is description in detail.
I'll work for next patch!

Thanks.
-Sidong

> 
> > 
> > Cc: Daniel Vetter <daniel@...ll.ch>
> > Cc: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>
> > Cc: Haneen Mohammed <hamohammed.sa@...il.com>
> > Cc: Melissa Wen <melissa.srw@...il.com>
> > 
> > Signed-off-by: Sidong Yang <realwakka@...il.com>
> > ---
> >  drivers/gpu/drm/vkms/vkms_crtc.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
> > index ac85e17428f8..09c012d54d58 100644
> > --- a/drivers/gpu/drm/vkms/vkms_crtc.c
> > +++ b/drivers/gpu/drm/vkms/vkms_crtc.c
> > @@ -86,6 +86,11 @@ static bool vkms_get_vblank_timestamp(struct drm_crtc *crtc,
> >  	struct vkms_output *output = &vkmsdev->output;
> >  	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
> >  
> > +	if (!READ_ONCE(vblank->enabled)) {
> > +		*vblank_time = ktime_get();
> > +		return true;
> > +	}
> > +
> 
> Apart from issues in commit message and format, I checked the code and it
> works fine.
> 
> Reviewed-by: Melissa Wen <melissa.srw@...il.com>
> 
> >  	*vblank_time = READ_ONCE(output->vblank_hrtimer.node.expires);
> >  
> >  	if (WARN_ON(*vblank_time == vblank->time))
> > -- 
> > 2.17.1
> >