linux-kernel - Re: [PATCH] nvme-pci: Force NVME_QUIRK_SIMPLE

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Message-ID: <867d7b15-6861-4300-83aa-55a6cdf87f58@oss.qualcomm.com>
Date: Fri, 25 Oct 2024 18:40:23 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Keith Busch <kbusch@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>
Cc: Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvme-pci: Force NVME_QUIRK_SIMPLE_SUSPEND on Qualcomm
 hosts

On 25.10.2024 6:12 PM, Keith Busch wrote:
> On Thu, Oct 24, 2024 at 07:33:07PM +0200, Konrad Dybcio wrote:
>> From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
>>
>> The Qualcomm SC8280XP SoC requires that all PCIe hosts are powered down
>> before the platform can reach S3-like sleep states. This is very much
>> similar in nature to the issue described in [1].
> 
> The "SIMPLE" quirk is only supposed to affect kernel managed runtime
> suspend states, s2idle or s0ix. Shouldn't s3 already be using the simple
> suspend?

So on these platforms, all system sleep states (incl. S3) are entered
through what Linux sees as s2idle, with a separate MCU doing a lot
behind the scenes. s2idle of course also covers the runtime cpuidle
cases.

All but the deepest state (which Linux doesn't differentiate as of
today) are effectively somewhat like s0ix.
It's a bit hard to draw accurate lines between Intel terminology and
what we have here, as there's way more things onboard than just the CPU
cluster that may be operating independently..

Konrad