Re: [Nouveau] [PATCH v2] drm/nouveau: Accept 'legacy' format modifiers

[James Jones <jajones@nvidia.com>]

On 7/29/20 7:47 AM, Kirill A. Shutemov wrote:
> On Wed, Jul 29, 2020 at 01:40:13PM +1000, Ben Skeggs wrote:
>> On Wed, 29 Jul 2020 at 12:48, Dave Airlie <airlied@gmail.com> wrote:
>>>
>>> On Tue, 28 Jul 2020 at 04:51, James Jones <jajones@nvidia.com> wrote:
>>>>
>>>> On 7/23/20 9:06 PM, Ben Skeggs wrote:
>>>>> On Sat, 18 Jul 2020 at 13:34, James Jones <jajones@nvidia.com> wrote:
>>>>>>
>>>>>> Accept the DRM_FORMAT_MOD_NVIDIA_16BX2_BLOCK()
>>>>>> family of modifiers to handle broken userspace
>>>>>> Xorg modesetting and Mesa drivers. Existing Mesa
>>>>>> drivers are still aware of only these older
>>>>>> format modifiers which do not differentiate
>>>>>> between different variations of the block linear
>>>>>> layout. When the format modifier support flag was
>>>>>> flipped in the nouveau kernel driver, the X.org
>>>>>> modesetting driver began attempting to use its
>>>>>> format modifier-enabled framebuffer path. Because
>>>>>> the set of format modifiers advertised by the
>>>>>> kernel prior to this change do not intersect with
>>>>>> the set of format modifiers advertised by Mesa,
>>>>>> allocating GBM buffers using format modifiers
>>>>>> fails and the modesetting driver falls back to
>>>>>> non-modifier allocation. However, it still later
>>>>>> queries the modifier of the GBM buffer when
>>>>>> creating its DRM-KMS framebuffer object, receives
>>>>>> the old-format modifier from Mesa, and attempts
>>>>>> to create a framebuffer with it. Since the kernel
>>>>>> is still not aware of these formats, this fails.
>>>>>>
>>>>>> Userspace should not be attempting to query format
>>>>>> modifiers of GBM buffers allocated with a non-
>>>>>> format-modifier-aware allocation path, but to
>>>>>> avoid breaking existing userspace behavior, this
>>>>>> change accepts the old-style format modifiers when
>>>>>> creating framebuffers and applying them to planes
>>>>>> by translating them to the equivalent new-style
>>>>>> modifier. To accomplish this, some layout
>>>>>> parameters must be assumed to match properties of
>>>>>> the device targeted by the relevant ioctls. To
>>>>>> avoid perpetuating misuse of the old-style
>>>>>> modifiers, this change does not advertise support
>>>>>> for them. Doing so would imply compatibility
>>>>>> between devices with incompatible memory layouts.
>>>>>>
>>>>>> Tested with Xorg 1.20 modesetting driver,
>>>>>> weston@c46c70dac84a4b3030cd05b380f9f410536690fc,
>>>>>> gnome & KDE wayland desktops from Ubuntu 18.04,
>>>>>> and sway 1.5
>>>>>>
>>>>>> Reported-by: Kirill A. Shutemov <kirill@shutemov.name>
>>>>>> Fixes: fa4f4c213f5f ("drm/nouveau/kms: Support NVIDIA format modifiers")
>>>>>> Link: https://lkml.org/lkml/2020/6/30/1251
>>>>>> Signed-off-by: James Jones <jajones@nvidia.com>
>>>>>> ---
>>>>>>    drivers/gpu/drm/nouveau/nouveau_display.c | 26 +++++++++++++++++++++--
>>>>>>    1 file changed, 24 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c
>>>>>> index 496c4621cc78..31543086254b 100644
>>>>>> --- a/drivers/gpu/drm/nouveau/nouveau_display.c
>>>>>> +++ b/drivers/gpu/drm/nouveau/nouveau_display.c
>>>>>> @@ -191,8 +191,14 @@ nouveau_decode_mod(struct nouveau_drm *drm,
>>>>>>                      uint32_t *tile_mode,
>>>>>>                      uint8_t *kind)
>>>>>>    {
>>>>>> +       struct nouveau_display *disp = nouveau_display(drm->dev);
>>>>>>           BUG_ON(!tile_mode || !kind);
>>>>>>
>>>>>> +       if ((modifier & (0xffull << 12)) == 0ull) {
>>>>>> +               /* Legacy modifier.  Translate to this device's 'kind.' */
>>>>>> +               modifier |= disp->format_modifiers[0] & (0xffull << 12);
>>>>>> +       }
>>>>> I believe this should be moved into the != MOD_LINEAR case.
>>>>
>>>> Yes, of course, thanks.  I need to re-evaluate my testing yet again to
>>>> make sure I hit that case too.  Preparing a v3...
>>>
>>> Going to need something here in the next day, two max.
>>>
>>> Linus may wait for another week, but it's not guaranteed.
>> I tested a whole bunch of GPUs before sending nouveau's -next tree,
>> and with the change I suggested to this patch + the other stuff I sent
>> through -fixes already, things seemed to be in OK shape.
> 
> JFYI, the adjusted (moved into != MOD_LINEAR case) patch works fine for me
> on top of drm-fixes-2020-07-29.

Sorry again for the delays (life is terrible lately), but the signed-off 
version with Ben's suggestion went out this morning, and I specifically 
tested linear modifiers in addition to retesting all the other test 
cases mentioned in the patch.

Thanks,
-James
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