Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Fri, 21 Jan 2022 20:00:49 +0100 | Subject | [Bug] nvme blocks PC10 since v5.15 - bisected |
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Hi Keith,
It is reported that the following commit
commit e5ad96f388b765fe6b52f64f37e910c0ba4f3de7 Author: Keith Busch <kbusch@kernel.org> Date: Tue Jul 27 09:40:44 2021 -0700
nvme-pci: disable hmb on idle suspend
An idle suspend may or may not disable host memory access from devices placed in low power mode. Either way, it should always be safe to disable the host memory buffer prior to entering the low power mode, and this should also always be faster than a full device shutdown.
Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Signed-off-by: Christoph Hellwig <hch@lst.de>
is the source of a serious power regression occurring since 5.15 (please see https://bugzilla.kernel.org/show_bug.cgi?id=215467).
After this commit, the SoC on the affected system cannot enter C-states deeper than PC2 while suspended to idle which basically defeats the purpose of suspending.
What may be happening is that nvme_disable_prepare_reset() that is not called any more in the ndev->nr_host_mem_descs case somehow causes the LTR of the device to change to "no requirement" which allows deeper C-states to be entered.
Can you have a look at this, please?
Cheers, Rafael
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