linux-kernel - Re: [PATCH v2] drm/amdgpu: register a dirty framebuffer callback for fbcon

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Date:   Wed, 16 Aug 2023 09:41:19 -0400
From:   Hamza Mahfooz <hamza.mahfooz@....com>
To:     Christian König <ckoenig.leichtzumerken@...il.com>,
        amd-gfx@...ts.freedesktop.org
Cc:     Srinivasan Shanmugam <srinivasan.shanmugam@....com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Guchun Chen <guchun.chen@....com>,
        dri-devel@...ts.freedesktop.org,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        stable@...r.kernel.org, linux-kernel@...r.kernel.org,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        Daniel Vetter <daniel@...ll.ch>,
        Alex Deucher <alexander.deucher@....com>,
        David Airlie <airlied@...il.com>,
        Christian König <christian.koenig@....com>,
        Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH v2] drm/amdgpu: register a dirty framebuffer callback for
 fbcon


On 8/16/23 01:55, Christian König wrote:
> 
> 
> Am 15.08.23 um 19:26 schrieb Hamza Mahfooz:
>> fbcon requires that we implement &drm_framebuffer_funcs.dirty.
>> Otherwise, the framebuffer might take a while to flush (which would
>> manifest as noticeable lag). However, we can't enable this callback for
>> non-fbcon cases since it might cause too many atomic commits to be made
>> at once. So, implement amdgpu_dirtyfb() and only enable it for fbcon
>> framebuffers on devices that support atomic KMS.
>>
>> Cc: Aurabindo Pillai <aurabindo.pillai@....com>
>> Cc: Mario Limonciello <mario.limonciello@....com>
>> Cc: stable@...r.kernel.org # 6.1+
>> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2519
>> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@....com>
>> ---
>> v2: update variable names
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_display.c | 26 ++++++++++++++++++++-
>>   1 file changed, 25 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
>> index d20dd3f852fc..d3b59f99cb7c 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
>> @@ -38,6 +38,8 @@
>>   #include <linux/pci.h>
>>   #include <linux/pm_runtime.h>
>>   #include <drm/drm_crtc_helper.h>
>> +#include <drm/drm_damage_helper.h>
>> +#include <drm/drm_drv.h>
>>   #include <drm/drm_edid.h>
>>   #include <drm/drm_fb_helper.h>
>>   #include <drm/drm_gem_framebuffer_helper.h>
>> @@ -532,11 +534,29 @@ bool amdgpu_display_ddc_probe(struct 
>> amdgpu_connector *amdgpu_connector,
>>       return true;
>>   }
>> +static int amdgpu_dirtyfb(struct drm_framebuffer *fb, struct drm_file 
>> *file,
>> +              unsigned int flags, unsigned int color,
>> +              struct drm_clip_rect *clips, unsigned int num_clips)
>> +{
>> +
>> +    if (strcmp(fb->comm, "[fbcon]"))
>> +        return -ENOSYS;
> 
> Once more to the v2 of this patch: Tests like those are a pretty big 
> NO-GO for upstreaming.

On closer inspection it is actually sufficient to check if `file` is
NULL here (since it means that the request isn't from userspace). So, do
you think that would be palatable for upstream?

> 
> Regards,
> Christian.
> 
>> +
>> +    return drm_atomic_helper_dirtyfb(fb, file, flags, color, clips,
>> +                     num_clips);
>> +}
>> +
>>   static const struct drm_framebuffer_funcs amdgpu_fb_funcs = {
>>       .destroy = drm_gem_fb_destroy,
>>       .create_handle = drm_gem_fb_create_handle,
>>   };
>> +static const struct drm_framebuffer_funcs amdgpu_fb_funcs_atomic = {
>> +    .destroy = drm_gem_fb_destroy,
>> +    .create_handle = drm_gem_fb_create_handle,
>> +    .dirty = amdgpu_dirtyfb
>> +};
>> +
>>   uint32_t amdgpu_display_supported_domains(struct amdgpu_device *adev,
>>                         uint64_t bo_flags)
>>   {
>> @@ -1139,7 +1159,11 @@ static int 
>> amdgpu_display_gem_fb_verify_and_init(struct drm_device *dev,
>>       if (ret)
>>           goto err;
>> -    ret = drm_framebuffer_init(dev, &rfb->base, &amdgpu_fb_funcs);
>> +    if (drm_drv_uses_atomic_modeset(dev))
>> +        ret = drm_framebuffer_init(dev, &rfb->base,
>> +                       &amdgpu_fb_funcs_atomic);
>> +    else
>> +        ret = drm_framebuffer_init(dev, &rfb->base, &amdgpu_fb_funcs);
>>       if (ret)
>>           goto err;
> 
-- 
Hamza