ACK/Cmnt: [PATCH 0/2][SRU][B][OEM-B] Power consumption during s2idle is higher than long idle(sk hynix)

[Stefan Bader]

On 06.11.18 11:53, AceLan Kao wrote:
> BugLink: https://bugs.launchpad.net/bugs/1801875
> 
> [Impact]
> On some Dell XPS models, we observed the power consumption raises higher
> than long idle does during s2idle with sk hynix nvme.
> 
> C2:
> Short idle: 4
> Long idle: 1
> S2I: 3.7
> S5: 0.19
> 
> C3:
> Short idle: 7.2
> Long idle: 4.5
> S2I: 6.22
> S5: 0.18
> 
> C5:
> Short idle: 6.5
> Long idle: 1
> S2I: 2.88
> S5: 0.18
> 
> [Fix]
> From SK hynix FE, MS Windows doesn't put nvme to D3, and uses its own
> APST feature to do the power management. To leverage its APST feature
> during s2idle, we can't disable nvme device while suspending, too.
> So, here is what we did on the driver, 1. prevent nvme from entering
> D3, 2. prevent nvme from being disabled when suspending.
> 
> [Test]
> Verified on different XPS machines with different sk hynix nvme disks,
> it fixes the power consumption issue with no regression. And the power
> consumption drops to 0.77W during s2idle.
> 
> [Regression Potential]
> Low, the patches only applied to specific nvme module, and from our
> test, the system is still stable.
> 
> [Misc]
> This issue should be fixed by the firmware, and we're pushing sk hynix
> to fix it. But before sk hynix find out how to solve it, we have to
> preserve these commits in our kernel for a while.
> BTW, the patches require pm_suspend_via_s2idle() function from below
> commit which is still under reviewing.
> https://lists.ubuntu.com/archives/kernel-team/2018-October/096141.html
> 
> AceLan Kao (2):
>   pci: prevent sk hynix nvme from entering D3
>   nvme: add quirk to not call disable function when suspending
> 
>  drivers/nvme/host/nvme.h | 5 +++++
>  drivers/nvme/host/pci.c  | 8 +++++++-
>  drivers/pci/quirks.c     | 1 +
>  include/linux/pci_ids.h  | 2 ++
>  4 files changed, 15 insertions(+), 1 deletion(-)
> 
Patches look reasonable and bug report has expected tasks. Just cover email is a
bit confusing because it does not list Cosmic at all.

Acked-by: Stefan Bader <stefan.bader at canonical.com>

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