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Date:   Thu, 8 Nov 2018 18:21:57 -0600
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     AceLan Kao <acelan.kao@canonical.com>
Cc:     Keith Busch <keith.busch@intel.com>, Jens Axboe <axboe@fb.com>,
        Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>,
        linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-pci@vger.kernel.org
Subject: Re: [PATCH v2 1/2] pci: prevent sk hynix nvme from entering D3
Message-ID: <20181109002157.GK41183@google.com>
References: <20181106071214.12745-1-acelan.kao@canonical.com>
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On Tue, Nov 06, 2018 at 03:12:13PM +0800, AceLan Kao wrote:
> It leads to the power consumption raises to 2.2W during s2idle, while
> it consumes less than 1W during long idle if put SK hynix nvme to D3
> and then enter s2idle.
> 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.

I don't know how APST works, but it sounds like you want to disable D3
if you're using APST.  But that's not what this patch does; this
disables it always.

I'm not sure we want a quirk for this at all, since as Christoph
points out, it doesn't fix a functional issue as the other uses of
quirk_no_ata_d3() do.

From your emails with Christoph, it sounds like this quirk is a
workaround for a firmware defect.  If we *do* end up wanting a quirk,
the changelog should at least mention the firmware defect and maybe
check whether it has been fixed.

> BTW, prevent it from entering D3 will increase the power consumtion around
> 0.13W ~ 0.15W during short/long idle, and the power consumption during
> s2idle becomes 0.77W.
> 
> Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
> ---
>  drivers/pci/quirks.c    | 1 +
>  include/linux/pci_ids.h | 2 ++
>  2 files changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 4700d24e5d55..b7e6492e8311 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -1332,6 +1332,7 @@ DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_AL, PCI_ANY_ID,
>     occur when mode detecting */
>  DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_VIA, PCI_ANY_ID,
>  				PCI_CLASS_STORAGE_IDE, 8, quirk_no_ata_d3);
> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SK_HYNIX, 0x1527, quirk_no_ata_d3);
>  
>  /*
>   * This was originally an Alpha-specific thing, but it really fits here.
> diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
> index 69f0abe1ba1a..5f5adda07de0 100644
> --- a/include/linux/pci_ids.h
> +++ b/include/linux/pci_ids.h
> @@ -3090,4 +3090,6 @@
>  
>  #define PCI_VENDOR_ID_NCUBE		0x10ff
>  
> +#define PCI_VENDOR_ID_SK_HYNIX		0x1c5c
> +
>  #endif /* _LINUX_PCI_IDS_H */
> -- 
> 2.17.1
> 
> 
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