linux-kernel - Re: [Regression] Commit "nvme/pci: Use host managed power state for suspend" has problems

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Date:   Wed, 7 Aug 2019 12:45:00 +0200
From:   Christoph Hellwig <hch@....de>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Keith Busch <kbusch@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Mario Limonciello <Mario.Limonciello@...l.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Keith Busch <keith.busch@...el.com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        linux-nvme <linux-nvme@...ts.infradead.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rajat Jain <rajatja@...gle.com>
Subject: Re: [Regression] Commit "nvme/pci: Use host managed power state
 for suspend" has problems

On Wed, Aug 07, 2019 at 11:48:33AM +0200, Rafael J. Wysocki wrote:
> So I think I know what the problem is here.
> 
> If ASPM is disabled for the NVMe device (which is the case on my machine by default),
> skipping the bus-level PM in nvme_suspend() causes the PCIe link of it to stay up and
> that prevents the SoC from getting into deeper package C-states.
> 
> If I change the ASPM policy to "powersave" (through the module parameter in there),
> ASPM gets enabled for the NVMe drive and I can get into PC10 via S2Idle with plain 5.3-rc3.
> 
> However, that's a bit less than straightforward, so I'm going to post a patch to make
> nvme_suspend() fall back to the "old ways" if ASPM is not enabled for the target device.

Sounds sensibel.

FYI your mail is not properly formatted and has way too long lines.