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SubjectRe: [PATCH 4.18 222/235] drm/amd/pp: Send khz clock values to DC for smu7/8
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On 2018-10-08 12:17 PM, Deucher, Alexander wrote:
>> -----Original Message-----
>> From: Sasha Levin <sashal@kernel.org>
>> Sent: Monday, October 8, 2018 10:49 AM
>> To: Deucher, Alexander <Alexander.Deucher@amd.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; linux-
>> kernel@vger.kernel.org; stable@vger.kernel.org; Wentland, Harry
>> <Harry.Wentland@amd.com>; Zhu, Rex <Rex.Zhu@amd.com>; Sasha Levin
>> <alexander.levin@microsoft.com>
>> Subject: Re: [PATCH 4.18 222/235] drm/amd/pp: Send khz clock values to DC
>> for smu7/8
>>
>> On Mon, Oct 08, 2018 at 02:33:56PM +0000, Deucher, Alexander wrote:
>>>> -----Original Message-----
>>>> From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>>> Sent: Monday, September 24, 2018 7:53 AM
>>>> To: linux-kernel@vger.kernel.org
>>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>;
>>>> stable@vger.kernel.org; Wentland, Harry <Harry.Wentland@amd.com>;
>>>> Deucher, Alexander <Alexander.Deucher@amd.com>; Zhu, Rex
>>>> <Rex.Zhu@amd.com>; Sasha Levin <alexander.levin@microsoft.com>
>>>> Subject: [PATCH 4.18 222/235] drm/amd/pp: Send khz clock values to DC
>>>> for
>>>> smu7/8
>>>>
>>>> 4.18-stable review patch. If anyone has any objections, please let me
>> know.
>>>>
>>>
>>> This regresses power usage on 4.18. Please revert.
>>> https://bugzilla.kernel.org/show_bug.cgi?id=201275
>>
>> Hi Alex,
>>
>> Thank you for the report.
>>
>> I'm working on improving this process, I'd be very grateful if you could
>> answer a few questions about this:
>>
>> 1. Is the same breakage seen upstream? (if so, it should be reverted there as
>> well and we can grab the revert into -stable).
>
> No regression in 4.19 or -next.
>
>> 2. Does the issue reported by this patch ("pipes seem to hang with a 4k DP
>> and 1080p HDMI display") exist in the 4.18 stable tree?
>
> I don't think so, but I'm not 100% sure. Harry, Rex do you know if this is a general issue or was it just fall out from the changes to the interface?
>

It was intended to deal with fallout to smu7/8 caused by the change to move the kHz-to-10kHz-conversion from display to powerplay. I believe that conversion initially overlooked these blocks. Rex, please correct me if I'm wrong. You probably know more about this than I do.

So yes, I agree, it was never intended to be used without the change to drop the *10 in display code, which was done with this change:

commit 23ec3d1479fd79658cd52c47618d8ddd2f32550b
Author: Rex Zhu <Rex.Zhu@amd.com>
Date: Mon Jun 18 18:15:15 2018 +0800

drm/amd/pp: Convert clock unit to KHz as defined

Convert clock unit 10KHz to KHz as the data sturct defined.
e.g.
struct pp_clock_with_latency {
uint32_t clocks_in_khz;
uint32_t latency_in_us;
};
Meanwhile revert the same conversion in display side.

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

I don't see this change in the 4.18.y stable tree. I probably should've caught that with the initial 4.18-stable review patch.

Harry

>> 3. If not, could you briefly explain why?
>
> We refactored the interface between the power and display components and this patch fixed up some of that fallout due to the differences in units used in each component.
>
>>
>>
>> The algorithm I use was very confident about this patch being stable material,
>> and when I looked at it back then (and again now) I was very confident of the
>> same. If I can understand where I was wrong I could improve my process.
>
> There are some other dependent patches required that were not flagged in the patch itself. IIRC, they were a bit big for stable.
>
> Alex
>

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