From: Kenneth Graunke <kenneth@whitecape.org>
To: "Rodrigo Vivi" <rodrigo.vivi@intel.com>,
"Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>,
"Jani Nikula" <jani.nikula@linux.intel.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
"André Almeida" <andrealmeid@collabora.com>
Cc: intel-gfx@lists.freedesktop.org, kernel@collabora.com,
dri-devel@lists.freedesktop.org
Subject: Re: Enabling sample_c optimization for Broadwell GPUs
Date: Wed, 05 May 2021 08:35:46 -0700 [thread overview]
Message-ID: <4570916.7zo566DRWU@mizzik> (raw)
In-Reply-To: <e99599bf-f503-3227-8361-afcd3d2a098f@collabora.com>
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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/198990f13e1d9429864c177d9441a6559771c5e2
>
> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=944115934436b1ff6cf773a9e9123858ea9ef3da
>
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prev parent reply other threads:[~2021-05-05 15:46 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-04 23:07 Enabling sample_c optimization for Broadwell GPUs André Almeida
2021-05-05 10:16 ` Rodrigo Vivi
2021-05-05 15:02 ` André Almeida
2021-05-05 15:35 ` Kenneth Graunke [this message]
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