Re: [PATCH 0/4] vkms: Switch to shadow-buffered plane state

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 12.07.21 um 13:56 schrieb Sumera Priyadarsini:
> On Mon, Jul 5, 2021 at 1:16 PM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>>
>> Vkms copies each plane's framebuffer into the output buffer; essentially
>> using a shadow buffer. DRM provides struct drm_shadow_plane_state, which
>> handles the details of mapping/unmapping shadow buffers into memory for
>> active planes.
>>
>> Convert vkms to the helpers. Makes vkms use shared code and gives more
>> test exposure to shadow-plane helpers.
>>
>> Thomas Zimmermann (4):
>>    drm/gem: Export implementation of shadow-plane helpers
>>    drm/vkms: Inherit plane state from struct drm_shadow_plane_state
>>    drm/vkms: Let shadow-plane helpers prepare the plane's FB
>>    drm/vkms: Use dma-buf mapping from shadow-plane state for composing
>>
>>   drivers/gpu/drm/drm_gem_atomic_helper.c | 55 ++++++++++++++++++++++--
>>   drivers/gpu/drm/vkms/vkms_composer.c    | 26 ++++++-----
>>   drivers/gpu/drm/vkms/vkms_drv.h         |  6 ++-
>>   drivers/gpu/drm/vkms/vkms_plane.c       | 57 ++++++-------------------
>>   include/drm/drm_gem_atomic_helper.h     |  6 +++
>>   5 files changed, 86 insertions(+), 64 deletions(-)
>>
>>
>> base-commit: 3d3b5479895dd6dd133571ded4318adf595708ba
>> --
>> 2.32.0
>>
> Hi,
> 
> Thanks for the patches. The switch to shadow-plane helpers also solved
> a bug that was causing a kernel
> panic during some IGT kms_flip subtests on the vkms virtual hw patch.

Melissa mention something like that as well and I don't really 
understand. Patch 3 removes an error message from the code, but is the 
actual bug also gone?

There's little difference between vkms' original code and the shared 
helper; except for the order of operations in prepare_fb. The shared 
helper synchronizes fences before mapping; vkms mapped first.

(Maybe the shared helper should warn about failed vmaps as well. But 
that's for another patch.)

Best regards
Thomas

> 
> Tested-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
> 
> Cheers,
> Sumera
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer


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