Re: [PATCH v2] PCI: Disable LTR on suspend for SSSTC 0x9100

[Mario Limonciello]

+Patrick Huang

On 3/17/22 08:10, Mario Limonciello wrote:
> Some drives from SSSTC are showing stability problems after s0i3
> entry when the Linux kernel is in s2idle loop if LTR has been
> enabled. This leads to failures to resume.
>
> This appears to be a firmware issue specific to SSSTC SSDs, so quirk
> them to avoid LTR being enabled during the suspend process.
>
> Link: https://lore.kernel.org/linux-nvme/20220315072233.GA2288@xxxxxx/T/#mb9b5782220a32e2c69fe37cf04ae1501b0f48221
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> ---
> changes from v1->v2:
>   * Move into a PCI quirk, handle entirely in PCI subsystem

Patrick has been running stress tests with this patch and reported a 
failure.  When it's figured out we will re-submit V3.

If any concerns to this approach in V2 though, comments still welcome.

Thanks,

>   drivers/pci/quirks.c    | 17 +++++++++++++++++
>   include/linux/pci_ids.h |  2 ++
>   2 files changed, 19 insertions(+)
>
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index d2dd6a6cda60..005142d574e7 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -5879,3 +5879,20 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x1533, rom_bar_overlap_defect);
>   DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x1536, rom_bar_overlap_defect);
>   DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x1537, rom_bar_overlap_defect);
>   DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x1538, rom_bar_overlap_defect);
> +
> +/*
> + * SSSTC firmware will continue to send LTR requests after device has entered D3
> + *
> + * This behavior causes problems when entering/exit s2idle, so avoid letting LTR
> + * be enabled during suspend.
> + */
> +static void ssstc_disable_ltr(struct pci_dev *pdev)
> +{
> +	pcie_capability_clear_word(pdev, PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_LTR_EN);
> +}
> +static void ssstc_enable_ltr(struct pci_dev *pdev)
> +{
> +	pcie_capability_set_word(pdev, PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_LTR_EN);
> +}
> +DECLARE_PCI_FIXUP_SUSPEND(PCI_VENDOR_ID_SSSTC, 0x9100, ssstc_disable_ltr);
> +DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_SSSTC, 0x9100, ssstc_enable_ltr);
> diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
> index 130949c3b486..ab47ccdd2ece 100644
> --- a/include/linux/pci_ids.h
> +++ b/include/linux/pci_ids.h
> @@ -2568,6 +2568,8 @@
>   #define PCI_VENDOR_ID_TEKRAM		0x1de1
>   #define PCI_DEVICE_ID_TEKRAM_DC290	0xdc29
>   
> +#define PCI_VENDOR_ID_SSSTC		0x1e95
> +
>   #define PCI_VENDOR_ID_TEHUTI		0x1fc9
>   #define PCI_DEVICE_ID_TEHUTI_3009	0x3009
>   #define PCI_DEVICE_ID_TEHUTI_3010	0x3010