[PATCH 3/3] drm/amdgpu:Limit the resolution for virtual_display

[Michel Dänzer]

On 2021-01-07 3:28 a.m., Deng, Emily wrote:
>> From: Michel Dänzer <michel at daenzer.net>
>> On 2021-01-06 11:40 a.m., Deng, Emily wrote:
>>>> From: Alex Deucher <alexdeucher at gmail.com> On Tue, Jan 5, 2021 at
>>>> 3:37 AM Emily.Deng <Emily.Deng at amd.com> wrote:
>>>>>
>>>>> Limit the resolution not bigger than 16384, which means
>>>>> dev->mode_info.num_crtc * common_modes[i].w not bigger than 16384.
>>>>>
>>>>> Signed-off-by: Emily.Deng <Emily.Deng at amd.com>
>>>>> ---
>>>>>    drivers/gpu/drm/amd/amdgpu/dce_virtual.c | 7 +++++--
>>>>>    1 file changed, 5 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/dce_virtual.c
>>>>> b/drivers/gpu/drm/amd/amdgpu/dce_virtual.c
>>>>> index 2b16c8faca34..c23d37b02fd7 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/dce_virtual.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/dce_virtual.c
>>>>> @@ -319,6 +319,7 @@ dce_virtual_encoder(struct drm_connector
>>>>> *connector)  static int dce_virtual_get_modes(struct drm_connector
>>>>> *connector)  {
>>>>>           struct drm_device *dev = connector->dev;
>>>>> +       struct amdgpu_device *adev = dev->dev_private;
>>>>>           struct drm_display_mode *mode = NULL;
>>>>>           unsigned i;
>>>>>           static const struct mode_size { @@ -350,8 +351,10 @@ static
>>>>> int dce_virtual_get_modes(struct drm_connector *connector)
>>>>>           };
>>>>>
>>>>>           for (i = 0; i < ARRAY_SIZE(common_modes); i++) {
>>>>> -               mode = drm_cvt_mode(dev, common_modes[i].w,
>>>> common_modes[i].h, 60, false, false, false);
>>>>> -               drm_mode_probed_add(connector, mode);
>>>>> +               if (adev->mode_info.num_crtc <= 4 ||
>>>>> + common_modes[i].w <= 2560) {
>>>>
>>>> You are also limiting the number of crtcs here.  Intended?  Won't
>>>> this break 5 or 6 crtc configs?
>>>>
>>>> Alex
>>> Yes, it is intended,  for num_crtc bigger then 4, don't support resolution
>> bigger then 2560, because of the max supported width is 16384 for xcb
>> protocol.
>>
>> There's no such limitation with Wayland. I'd recommend against artificially
>> imposing limits from X11 to the kernel.
>>
>>
>> (As a side note, the X11 protocol limit should actually be 32768; the
>> 16384 limit exposed in the RANDR extension comes from the kernel driver,
>> specifically drmModeGetResources's max_width/height)
> It is our test and debug result, that the follow variable only have 16bit. Will limit the resolution to 16384.
> glamor_pixmap_from_fd(ScreenPtr screen,
>                        int fd,
>                        CARD16 width,
>                        CARD16 height,
>                        CARD16 stride, CARD8 depth, CARD8 bpp)

I assume you're referring to the stride parameter, which is in bytes.

This function is only used for pixmaps created from a dma-buf via DRI3. 
It does not limit the size of other pixmaps, so it does not limit the 
size of the screen pixmap (which corresponds to the framebuffer size in 
the RANDR extension) in general.

Also, this is an implementation detail, the limitation could be lifted 
by changing the type of the parameter (though that would be an ABI break 
for Xorg).

Xwayland isn't affected by this:

Screen 0: minimum 16 x 16, current 1920 x 1200, maximum 32767 x 32767


-- 
Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer