* Enabling sample_c optimization for Broadwell GPUs
@ 2021-05-04 23:07 André Almeida
2021-05-05 10:16 ` [Intel-gfx] " Rodrigo Vivi
2021-05-05 15:35 ` [Intel-gfx] " Kenneth Graunke
0 siblings, 2 replies; 7+ messages in thread
From: André Almeida @ 2021-05-04 23:07 UTC (permalink / raw)
To: Rodrigo Vivi, Joonas Lahtinen, Jani Nikula, Daniel Vetter,
Kenneth Graunke
Cc: intel-gfx, kernel, dri-devel
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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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Enabling sample_c optimization for Broadwell GPUs
2021-05-04 23:07 Enabling sample_c optimization for Broadwell GPUs André Almeida
@ 2021-05-05 10:16 ` Rodrigo Vivi
2021-05-05 15:35 ` [Intel-gfx] " Kenneth Graunke
1 sibling, 0 replies; 7+ messages in thread
From: Rodrigo Vivi @ 2021-05-05 10:16 UTC (permalink / raw)
To: André Almeida; +Cc: intel-gfx, dri-devel, Kenneth Graunke, kernel
Hi Andre,
I'm not familiar with the sample c message optimization.
Probably Ken can comment.
However I could check the internal spec here and I saw this bit
only exists with this meaning in Haswell.
For all the other platforms, including Broadwell it got re-purposed with
a different meaning and a programming note:
"This bit should be programmed to zero (0h) at all times."
Also, I could not find any workaround documented anywhere recommending
this bit to be set.
So, I would not recommend to use it in any product, even downstream.
Regardless the state of sample c message optimization in later platforms.
Thanks,
Rodrigo.
On Tue, May 04, 2021 at 08:07:14PM -0300, 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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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Intel-gfx] Enabling sample_c optimization for Broadwell GPUs
@ 2021-05-05 10:16 ` Rodrigo Vivi
0 siblings, 0 replies; 7+ messages in thread
From: Rodrigo Vivi @ 2021-05-05 10:16 UTC (permalink / raw)
To: André Almeida; +Cc: intel-gfx, dri-devel, Kenneth Graunke, kernel
Hi Andre,
I'm not familiar with the sample c message optimization.
Probably Ken can comment.
However I could check the internal spec here and I saw this bit
only exists with this meaning in Haswell.
For all the other platforms, including Broadwell it got re-purposed with
a different meaning and a programming note:
"This bit should be programmed to zero (0h) at all times."
Also, I could not find any workaround documented anywhere recommending
this bit to be set.
So, I would not recommend to use it in any product, even downstream.
Regardless the state of sample c message optimization in later platforms.
Thanks,
Rodrigo.
On Tue, May 04, 2021 at 08:07:14PM -0300, 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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https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Enabling sample_c optimization for Broadwell GPUs
2021-05-05 10:16 ` [Intel-gfx] " Rodrigo Vivi
@ 2021-05-05 15:02 ` André Almeida
-1 siblings, 0 replies; 7+ messages in thread
From: André Almeida @ 2021-05-05 15:02 UTC (permalink / raw)
To: Rodrigo Vivi; +Cc: intel-gfx, dri-devel, Kenneth Graunke, kernel
Hi Rodrigo,
Thank you very much for providing that information in a precise manner.
Às 07:16 de 05/05/21, Rodrigo Vivi escreveu:
> Hi Andre,
>
> I'm not familiar with the sample c message optimization.
> Probably Ken can comment.
>
> However I could check the internal spec here and I saw this bit
> only exists with this meaning in Haswell.
>
> For all the other platforms, including Broadwell it got re-purposed with
> a different meaning and a programming note:
> "This bit should be programmed to zero (0h) at all times."
>
> Also, I could not find any workaround documented anywhere recommending
> this bit to be set.
>
> So, I would not recommend to use it in any product, even downstream.
> Regardless the state of sample c message optimization in later platforms.
>
> Thanks,
> Rodrigo.
>
> On Tue, May 04, 2021 at 08:07:14PM -0300, 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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dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Intel-gfx] Enabling sample_c optimization for Broadwell GPUs
@ 2021-05-05 15:02 ` André Almeida
0 siblings, 0 replies; 7+ messages in thread
From: André Almeida @ 2021-05-05 15:02 UTC (permalink / raw)
To: Rodrigo Vivi; +Cc: intel-gfx, dri-devel, Kenneth Graunke, kernel
Hi Rodrigo,
Thank you very much for providing that information in a precise manner.
Às 07:16 de 05/05/21, Rodrigo Vivi escreveu:
> Hi Andre,
>
> I'm not familiar with the sample c message optimization.
> Probably Ken can comment.
>
> However I could check the internal spec here and I saw this bit
> only exists with this meaning in Haswell.
>
> For all the other platforms, including Broadwell it got re-purposed with
> a different meaning and a programming note:
> "This bit should be programmed to zero (0h) at all times."
>
> Also, I could not find any workaround documented anywhere recommending
> this bit to be set.
>
> So, I would not recommend to use it in any product, even downstream.
> Regardless the state of sample c message optimization in later platforms.
>
> Thanks,
> Rodrigo.
>
> On Tue, May 04, 2021 at 08:07:14PM -0300, 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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Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Enabling sample_c optimization for Broadwell GPUs
2021-05-04 23:07 Enabling sample_c optimization for Broadwell GPUs André Almeida
@ 2021-05-05 15:35 ` Kenneth Graunke
2021-05-05 15:35 ` [Intel-gfx] " Kenneth Graunke
1 sibling, 0 replies; 7+ messages in thread
From: Kenneth Graunke @ 2021-05-05 15:35 UTC (permalink / raw)
To: Rodrigo Vivi, Joonas Lahtinen, Jani Nikula, Daniel Vetter,
André Almeida
Cc: intel-gfx, kernel, dri-devel
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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
>
[-- Attachment #1.2: This is a digitally signed message part. --]
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Intel-gfx] Enabling sample_c optimization for Broadwell GPUs
@ 2021-05-05 15:35 ` Kenneth Graunke
0 siblings, 0 replies; 7+ messages in thread
From: Kenneth Graunke @ 2021-05-05 15:35 UTC (permalink / raw)
To: Rodrigo Vivi, Joonas Lahtinen, Jani Nikula, Daniel Vetter,
André Almeida
Cc: intel-gfx, kernel, dri-devel
[-- Attachment #1.1: Type: text/plain, Size: 1334 bytes --]
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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[-- Attachment #2: Type: text/plain, Size: 160 bytes --]
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^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-05-06 9:37 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-05-04 23:07 Enabling sample_c optimization for Broadwell GPUs André Almeida
2021-05-05 10:16 ` Rodrigo Vivi
2021-05-05 10:16 ` [Intel-gfx] " Rodrigo Vivi
2021-05-05 15:02 ` André Almeida
2021-05-05 15:02 ` [Intel-gfx] " André Almeida
2021-05-05 15:35 ` Kenneth Graunke
2021-05-05 15:35 ` [Intel-gfx] " Kenneth Graunke
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