Hello,
Yes, that bit only exists on Haswell. On Haswell, sample_c operations were processed at 1 pixel/clock unless you set that bit, in which case they get processed at 4 pixels/clock. The downside is that it breaks some obscure media feature that apparently no one used.
Broadwell and later alway process sample_c operations at the fast speed, and there is no bit to control it. I would say that downstream patch is incorrect.
--Ken
On Tuesday, May 4, 2021 4:07:14 PM PDT André Almeida wrote:
Hi there,
While browsing an old downstream kernel, I found a patch[0] that enables sample_c optimizations at Broadwell GPUs. The message from the upstream commit that enables it for Haswell[1] (and presumably where the code at[0] was copied from) states that "[..] later platforms remove this bit, and apparently always enable the optimization".
Could you confirm that Broadwell and following architectures enable this optimization by default (and thus, patch[0] is a no-op), or should I upstream it?
Thanks, André
[0] https://github.com/ValveSoftware/steamos_kernel/commit/198990f13e1d9429864c1...
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...