Re: [Outreachy kernel] [PATCH 1/2] drm/amd/amdgpu/amdgpu_device.c: Replace drm_modeset_*_all with DRM_MODESET_LOCK_ALL_*

From: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To: Julia Lawall <julia.lawall@inria.fr>
Cc: "David Airlie" <airlied@linux.ie>,
	dri-devel@lists.freedesktop.org,
	"Melissa Wen" <melissa.srw@gmail.com>,
	outreachy-kernel@googlegroups.com,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [Outreachy kernel] [PATCH 1/2] drm/amd/amdgpu/amdgpu_device.c: Replace drm_modeset_*_all with DRM_MODESET_LOCK_ALL_*
Date: Mon, 19 Apr 2021 15:51:43 +0200	[thread overview]
Message-ID: <4883020.1eLjRNAHnk@linux.local> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2104191506110.16374@hadrien>

On Monday, April 19, 2021 3:08:51 PM CEST Julia Lawall wrote:
> On Mon, 19 Apr 2021, Fabio M. De Francesco wrote:
> > Replace the deprecated API with new helpers, according to the TODO list
> > of the DRM subsystem.
> 
> The commit message will perhaps not be very meaningful one year from now.
> You could say for example DRM_MODESET_LOCK_ALL_BEGIN was introduced in
> commit XXX (there is a proper format for referring to other commits) for
> what purpose.  And then say that you are making the replacement.
> 
> Actually, I'm a little surprised to see something that looks like a
> function call be replaced by something that looks like a macro.  Maybe it
> was a macro all along, and this is just making that more clear.  In any
> case, if I were to look at this commit, I would appreciate a little more
> context information.
> 
> julia
>
I have made that message in line with an old commit (9bcaa3fe58ab) that had 
been taken by D. Vetter (the DRM maintainer). That message didn't explain more 
than referring to the TODO list. I try to stick with each subsystem's  
conventions.

However, I agree with you: referring to a TODO list, which some day  will 
surely change, is not the best means to provide context information.

From that macro documentation (https://dri.freedesktop.org/docs/drm/gpu/drm-kms.html#c.DRM_MODESET_LOCK_ALL_BEGIN):

"DRM_MODESET_LOCK_ALL_BEGIN  simplifies grabbing all modeset locks using a 
local context. This has the advantage of reducing boilerplate, [...]". 
(Please, note that I haven't copied the last part of the paragraph because it 
talks about checking the return value but I think it's useless because the 
only possible return value is 0).

If more context information is needed, I would add the above-mentioned note to 
my commit message and submit a v2 patch.

Is it the right way to solve the issue that you pointed out?

Thanks in advance,

Fabio
> 
> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> > ---
> > 
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 18 ++++++++++++------
> >  1 file changed, 12 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c index
> > 6447cd6ca5a8..e1a71579f8e6 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > @@ -32,6 +32,7 @@
> > 
> >  #include <linux/slab.h>
> >  
> >  #include <drm/drm_atomic_helper.h>
> > 
> > +#include <drm/drm_drv.h>
> > 
> >  #include <drm/drm_probe_helper.h>
> >  #include <drm/amdgpu_drm.h>
> >  #include <linux/vgaarb.h>
> > 
> > @@ -3694,14 +3695,17 @@ int amdgpu_device_suspend(struct drm_device *dev,
> > bool fbcon)> 
> >  	if (!amdgpu_device_has_dc_support(adev)) {
> >  	
> >  		/* turn off display hw */
> > 
> > -		drm_modeset_lock_all(dev);
> > +		struct drm_modeset_acquire_ctx ctx;
> > +		int ret;
> > +
> > +		DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, ret);
> > 
> >  		drm_connector_list_iter_begin(dev, &iter);
> >  		drm_for_each_connector_iter(connector, &iter)
> >  		
> >  			drm_helper_connector_dpms(connector,
> >  			
> >  						  
DRM_MODE_DPMS_OFF);
> >  		
> >  		drm_connector_list_iter_end(&iter);
> > 
> > -		drm_modeset_unlock_all(dev);
> > -			/* unpin the front buffers and cursors */
> > +		DRM_MODESET_LOCK_ALL_END(dev, ctx, ret);
> > +		/* unpin the front buffers and cursors */
> > 
> >  		list_for_each_entry(crtc, &dev->mode_config.crtc_list, 
head) {
> >  		
> >  			struct amdgpu_crtc *amdgpu_crtc = 
to_amdgpu_crtc(crtc);
> >  			struct drm_framebuffer *fb = crtc->primary-
>fb;
> > 
> > @@ -3830,19 +3834,21 @@ int amdgpu_device_resume(struct drm_device *dev,
> > bool fbcon)> 
> >  	/* blat the mode back in */
> >  	if (fbcon) {
> >  	
> >  		if (!amdgpu_device_has_dc_support(adev)) {
> > 
> > +			struct drm_modeset_acquire_ctx ctx;
> > +			int ret;
> > +
> > 
> >  			/* pre DCE11 */
> >  			drm_helper_resume_force_mode(dev);
> >  			
> >  			/* turn on display hw */
> > 
> > -			drm_modeset_lock_all(dev);
> > +			DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, 
ret);
> > 
> >  			drm_connector_list_iter_begin(dev, &iter);
> >  			drm_for_each_connector_iter(connector, 
&iter)
> >  			
> >  				
drm_helper_connector_dpms(connector,
> >  				
> >  							  
DRM_MODE_DPMS_ON);
> >  			
> >  			drm_connector_list_iter_end(&iter);
> > 
> > -
> > -			drm_modeset_unlock_all(dev);
> > +			DRM_MODESET_LOCK_ALL_END(dev, ctx, ret);
> > 
> >  		}
> >  		amdgpu_fbdev_set_suspend(adev, 0);
> >  	
> >  	}
> > 
> > --
> > 2.31.1
> > 
> > --
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> > https://groups.google.com/d/msgid/outreachy-kernel/20210419122059.738-2-fmd
> > efrancesco%40gmail.com.

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