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SubjectRe: [PATCH v3] pci: prevent putting nvidia GPUs into lower device states on certain intel bridges
On Wed, Oct 16, 2019 at 04:44:49PM +0200, Karol Herbst wrote:
> Fixes state transitions of Nvidia Pascal GPUs from D3cold into higher device
> states.
>
> v2: convert to pci_dev quirk
> put a proper technical explanation of the issue as a in-code comment
> v3: disable it only for certain combinations of intel and nvidia hardware
>
> Signed-off-by: Karol Herbst <kherbst@redhat.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
> Cc: Mika Westerberg <mika.westerberg@intel.com>
> Cc: linux-pci@vger.kernel.org
> Cc: linux-pm@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Cc: nouveau@lists.freedesktop.org
> ---
> drivers/pci/pci.c | 11 ++++++++++
> drivers/pci/quirks.c | 52 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/pci.h | 1 +
> 3 files changed, 64 insertions(+)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b97d9e10c9cc..8e056eb7e6ff 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -805,6 +805,13 @@ static inline bool platform_pci_bridge_d3(struct pci_dev *dev)
> return pci_platform_pm ? pci_platform_pm->bridge_d3(dev) : false;
> }
>
> +static inline bool parent_broken_child_pm(struct pci_dev *dev)
> +{
> + if (!dev->bus || !dev->bus->self)
> + return false;
> + return dev->bus->self->broken_nv_runpm && dev->broken_nv_runpm;
> +}
> +
> /**
> * pci_raw_set_power_state - Use PCI PM registers to set the power state of
> * given PCI device
> @@ -850,6 +857,10 @@ static int pci_raw_set_power_state(struct pci_dev *dev, pci_power_t state)
> || (state == PCI_D2 && !dev->d2_support))
> return -EIO;
>
> + /* check if the bus controller causes issues */
> + if (state != PCI_D0 && parent_broken_child_pm(dev))
> + return 0;
> +
> pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
>
> /*
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 44c4ae1abd00..c2f20b745dd4 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -5268,3 +5268,55 @@ static void quirk_reset_lenovo_thinkpad_p50_nvgpu(struct pci_dev *pdev)
> DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_NVIDIA, 0x13b1,
> PCI_CLASS_DISPLAY_VGA, 8,
> quirk_reset_lenovo_thinkpad_p50_nvgpu);
> +
> +/*
> + * Some Intel PCIe bridges cause devices to disappear from the PCIe bus after
> + * those were put into D3cold state if they were put into a non D0 PCI PM
> + * device state before doing so.
> + *
> + * This leads to various issue different issues which all manifest differently,
> + * but have the same root cause:
> + * - AIML code execution hits an infinite loop (as the coe waits on device
> + * memory to change).
> + * - kernel crashes, as all pci reads return -1, which most code isn't able
> + * to handle well enough.
> + * - sudden shutdowns, as the kernel identified an unrecoverable error after
> + * userspace tries to access the GPU.
> + *
> + * In all cases dmesg will contain at least one line like this:
> + * 'nouveau 0000:01:00.0: Refused to change power state, currently in D3'
> + * followed by a lot of nouveau timeouts.
> + *
> + * ACPI code writes bit 0x80 to the not documented PCI register 0x248 of the
> + * PCIe bridge controller in order to power down the GPU.
> + * Nonetheless, there are other code paths inside the ACPI firmware which use
> + * other registers, which seem to work fine:
> + * - 0xbc bit 0x20 (publicly available documentation claims 'reserved')
> + * - 0xb0 bit 0x10 (link disable)
> + * Changing the conditions inside the firmware by poking into the relevant
> + * addresses does resolve the issue, but it seemed to be ACPI private memory
> + * and not any device accessible memory at all, so there is no portable way of
> + * changing the conditions.
> + *
> + * The only systems where this behavior can be seen are hybrid graphics laptops
> + * with a secondary Nvidia Pascal GPU. It cannot be ruled out that this issue
> + * only occurs in combination with listed Intel PCIe bridge controllers and
> + * the mentioned GPUs or if it's only a hw bug in the bridge controller.
> + *
> + * But because this issue was NOT seen on laptops with an Nvidia Pascal GPU
> + * and an Intel Coffee Lake SoC, there is a higher chance of there being a bug
> + * in the bridge controller rather than in the GPU.
> + *
> + * This issue was not able to be reproduced on non laptop systems.
> + */
> +
> +static void quirk_broken_nv_runpm(struct pci_dev *dev)
> +{
> + dev->broken_nv_runpm = 1;

Can you use the existing PCI_DEV_FLAGS_NO_D3 flag for this instead of
adding a new flag?

I would put the parent_broken_child_pm() logic here, if possible,
e.g., something like:

struct pci_dev *bridge = pci_upstream_bridge(dev);

if (bridge &&
bridge->vendor == PCI_VENDOR_ID_INTEL && bridge->device == 0x1901)
dev->dev_flags |= PCI_DEV_FLAGS_NO_D3;

> +}
> +DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
> + PCI_BASE_CLASS_DISPLAY, 16,
> + quirk_broken_nv_runpm);
> +/* kaby lake */
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x1901,
> + quirk_broken_nv_runpm);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index ac8a6c4e1792..903a0b3a39ec 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -416,6 +416,7 @@ struct pci_dev {
> unsigned int __aer_firmware_first_valid:1;
> unsigned int __aer_firmware_first:1;
> unsigned int broken_intx_masking:1; /* INTx masking can't be used */
> + unsigned int broken_nv_runpm:1; /* some combinations of intel bridge controller and nvidia GPUs break rtd3 */
> unsigned int io_window_1k:1; /* Intel bridge 1K I/O windows */
> unsigned int irq_managed:1;
> unsigned int has_secondary_link:1;
> --
> 2.21.0
>

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