linux-kernel - Re: [PATCH 1/5] drm/solomon: Move calls to drm_gem_fb_end

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Message-ID: <0b6cb807-1a7e-427e-af42-dfc8f422f813@suse.de>
Date: Wed, 17 Sep 2025 11:20:22 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Javier Martinez Canillas <javierm@...hat.com>,
 Iker Pedrosa <ikerpedrosam@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] drm/solomon: Move calls to drm_gem_fb_end_cpu*()

grr, I should have noticed that before giving the r-b

Am 17.09.25 um 11:06 schrieb Javier Martinez Canillas:
> Iker Pedrosa <ikerpedrosam@...il.com> writes:
>
> Hello Iker,
>
> Thanks for your patch.
>
>> Calls to drm_gem_fb_end_cpu*() should be between the calls to
>> drm_dev*(), and not hidden inside some other function. This way the
>> critical section code is visible at a glance, keeping it short and
>> improving maintainability.
>>
>> Signed-off-by: Iker Pedrosa <ikerpedrosam@...il.com>
>> ---
>>   drivers/gpu/drm/solomon/ssd130x.c | 33 +++++++++++++++------------------
>>   1 file changed, 15 insertions(+), 18 deletions(-)
>>
> [...]
>
>> @@ -1232,6 +1214,9 @@ static void ssd130x_primary_plane_atomic_update(struct drm_plane *plane,
>>   	if (!drm_dev_enter(drm, &idx))
>>   		return;
>>   
>> +	if (drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE))
>> +		return;
>> +
> In this error path you should call drm_dev_exit(). The convention in the
> kernel usually is to have a goto label for this, e.g.:
>
>         if (drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE))
>                goto out_drm_dev_exit;
>
>>   	drm_atomic_helper_damage_iter_init(&iter, old_plane_state, plane_state);
>>   	drm_atomic_for_each_plane_damage(&iter, &damage) {
>>   		dst_clip = plane_state->dst;
>> @@ -1245,6 +1230,8 @@ static void ssd130x_primary_plane_atomic_update(struct drm_plane *plane,
>>   				     &shadow_plane_state->fmtcnv_state);
>>   	}
>>   
>> +	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
>> +
> and then here before the call you could have the label.
>
> out_drm_dev_exit:
>
>>   	drm_dev_exit(idx);
> Same comments for the other places where you are adding the
> drm_gem_fb_end_cpu*() calls next to the drm_dev*() ones.
>
> After the mentioned changes:
>
> Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)