3e2926f875
The value of the AFBC_FEATURES register is required by userspace to determine AFBC support on Bifrost. A user on our IRC channel (#panfrost) reported a workload that raised a fault on one system's Mali G31 but worked flawlessly with another system's Mali G31. We determined the cause to be missing AFBC support on one vendor's Mali implementation -- it turns out AFBC is optional on Bifrost! Whether AFBC is supported or not is exposed in the AFBC_FEATURES register on Bifrost, which reads back as 0 on Midgard. A zero value indicates AFBC is fully supported, provided the architecture itself supports AFBC, allowing backwards-compatibility with Midgard. Bits 0 and 15 indicate that AFBC support is absent for texturing and rendering respectively. The user experiencing the fault reports that AFBC_FEATURES reads back 0x10001 on their system, confirming the architectural lack of AFBC. Userspace needs this parameter to know to disable AFBC on that chip, and perhaps others. v2: Fix typo from copy-paste fail. v3: Bump the UABI version. This commit was cherry-picked from another series so chalking this up to a rebase fail. Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com> Reviewed-by: Steven Price <steven.price@arm.com> Cc: Rob Herring <robh@kernel.org> Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com> Signed-off-by: Steven Price <steven.price@arm.com> Link: https://patchwork.freedesktop.org/patch/msgid/20210604130011.3203-1-alyssa.rosenzweig@collabora.com |
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