Re: [PATCH 1/2] Revert "xhci: Enable RPM on controllers that support low-power states"

From: Basavaraj Natikar <bnatikar@amd.com>
To: Mathias Nyman <mathias.nyman@linux.intel.com>,
	gregkh@linuxfoundation.org
Cc: linux-usb@vger.kernel.org, linux-bluetooth@vger.kernel.org,
	mario.limonciello@amd.com, regressions@lists.linux.dev,
	regressions@leemhuis.info, Basavaraj.Natikar@amd.com,
	pmenzel@molgen.mpg.de, bugs-a21@moonlit-rail.com,
	stable@vger.kernel.org
Subject: Re: [PATCH 1/2] Revert "xhci: Enable RPM on controllers that support low-power states"
Date: Mon, 4 Dec 2023 20:59:35 +0530	[thread overview]
Message-ID: <e0781c30-a22e-40b5-a387-bae92672c2cd@amd.com> (raw)
In-Reply-To: <273a8811-f34e-dbe7-c301-bb796ddcced1@linux.intel.com>

On 12/4/2023 8:36 PM, Mathias Nyman wrote:
> On 4.12.2023 16.49, Basavaraj Natikar wrote:
>>
>> On 12/4/2023 7:52 PM, Mathias Nyman wrote:
>>> On 4.12.2023 12.49, Basavaraj Natikar wrote:
>>>>
>>>> On 12/4/2023 3:38 PM, Mathias Nyman wrote:
>>>>> This reverts commit a5d6264b638efeca35eff72177fd28d149e0764b.
>>>>>
>>>>> This patch was an attempt to solve issues seen when enabling
>>>>> runtime PM
>>>>> as default for all AMD 1.1 xHC hosts. see commit 4baf12181509
>>>>> ("xhci: Loosen RPM as default policy to cover for AMD xHC 1.1")
>>>>
>>>> AFAK, only 4baf12181509 commit has regression on AMD xHc 1.1 below is
>>>> not regression
>>>> patch and its unrelated to AMD xHC 1.1.
>>>>
>>>> Only [PATCH 2/2] Revert "xhci: Loosen RPM as default policy to cover
>>>> for AMD xHC 1.1"
>>>> alone in this series solves regression issues.
>>>>
>>>
>>> Patch a5d6264b638e ("xhci: Enable RPM on controllers that support
>>> low-power states")
>>> was originally not supposed to go to stable. It was added later as it
>>> solved some
>>> cases triggered by 4baf12181509 ("xhci: Loosen RPM as default policy
>>> to cover for AMD xHC 1.1")
>>> see:
>>> https://lore.kernel.org/linux-usb/5993222.lOV4Wx5bFT@natalenko.name/
>>>
>>> Turns out it wasn't enough.
>>>
>>> If we now revert 4baf12181509 "xhci: Loosen RPM as default policy to
>>> cover for AMD xHC 1.1"
>>> I still think it makes sense to also revert a5d6264b638e.
>>> Especially from the stable kernels.
>>
>> Yes , a5d6264b638e still solves other issues if underlying hardware
>> doesn't support RPM
>> if we revert a5d6264b638e on stable releases then new issues (not
>> related to regression)
>> other than AMD xHC 1.1 controllers including xHC 1.2 will still exist
>> on stable releases.
>
> Ok, got it, so a5d6264b638e also solves other issues than those
> exposed by 4baf12181509.
> And that one (a5d6264b638) should originally have been marked for stable.
>
> So only revert 4baf12181509, PATCH 2/2 in this series

Thank you, that is correct.

Thanks,
--
Basavaraj

>
> Thanks
> Mathias