Re: [PATCH V2] PCI: Move VMD ASPM/LTR fix to PCI quirk

[Ville Syrjälä]

On Tue, Apr 11, 2023 at 02:33:23PM -0700, David E. Box wrote:
> In commit f492edb40b54 ("PCI: vmd: Add quirk to configure PCIe ASPM and
> LTR") the VMD driver calls pci_enabled_link_state as a callback from
> pci_bus_walk. Both will acquire the pci_bus_sem lock leading to a lockdep
> warning. Instead of doing the pci_bus_walk, move the fix to quirks.c using
> DECLARE_PCI_FIXUP_FINAL.

What happened to this patch? We're still carrying a local fix
for this in drm-tip...

> 
> Fixes: f492edb40b54 ("PCI: vmd: Add quirk to configure PCIe ASPM and LTR")
> Suggested-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Signed-off-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx>
> ---
> 
> V2 - Instead of adding a lock flag argument to pci_enabled_link_state, move
>      the fix to quirks.c
> 
>  drivers/pci/controller/vmd.c | 55 +--------------------------
>  drivers/pci/quirks.c         | 72 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 73 insertions(+), 54 deletions(-)
> 
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index 990630ec57c6..47fa3e5f2dc5 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -66,22 +66,11 @@ enum vmd_features {
>  	 * interrupt handling.
>  	 */
>  	VMD_FEAT_CAN_BYPASS_MSI_REMAP		= (1 << 4),
> -
> -	/*
> -	 * Enable ASPM on the PCIE root ports and set the default LTR of the
> -	 * storage devices on platforms where these values are not configured by
> -	 * BIOS. This is needed for laptops, which require these settings for
> -	 * proper power management of the SoC.
> -	 */
> -	VMD_FEAT_BIOS_PM_QUIRK		= (1 << 5),
>  };
>  
> -#define VMD_BIOS_PM_QUIRK_LTR	0x1003	/* 3145728 ns */
> -
>  #define VMD_FEATS_CLIENT	(VMD_FEAT_HAS_MEMBAR_SHADOW_VSCAP |	\
>  				 VMD_FEAT_HAS_BUS_RESTRICTIONS |	\
> -				 VMD_FEAT_OFFSET_FIRST_VECTOR |		\
> -				 VMD_FEAT_BIOS_PM_QUIRK)
> +				 VMD_FEAT_OFFSET_FIRST_VECTOR)
>  
>  static DEFINE_IDA(vmd_instance_ida);
>  
> @@ -724,46 +713,6 @@ static void vmd_copy_host_bridge_flags(struct pci_host_bridge *root_bridge,
>  	vmd_bridge->native_dpc = root_bridge->native_dpc;
>  }
>  
> -/*
> - * Enable ASPM and LTR settings on devices that aren't configured by BIOS.
> - */
> -static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
> -{
> -	unsigned long features = *(unsigned long *)userdata;
> -	u16 ltr = VMD_BIOS_PM_QUIRK_LTR;
> -	u32 ltr_reg;
> -	int pos;
> -
> -	if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
> -		return 0;
> -
> -	pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL);
> -
> -	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
> -	if (!pos)
> -		return 0;
> -
> -	/*
> -	 * Skip if the max snoop LTR is non-zero, indicating BIOS has set it
> -	 * so the LTR quirk is not needed.
> -	 */
> -	pci_read_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, &ltr_reg);
> -	if (!!(ltr_reg & (PCI_LTR_VALUE_MASK | PCI_LTR_SCALE_MASK)))
> -		return 0;
> -
> -	/*
> -	 * Set the default values to the maximum required by the platform to
> -	 * allow the deepest power management savings. Write as a DWORD where
> -	 * the lower word is the max snoop latency and the upper word is the
> -	 * max non-snoop latency.
> -	 */
> -	ltr_reg = (ltr << 16) | ltr;
> -	pci_write_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, ltr_reg);
> -	pci_info(pdev, "VMD: Default LTR value set by driver\n");
> -
> -	return 0;
> -}
> -
>  static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>  {
>  	struct pci_sysdata *sd = &vmd->sysdata;
> @@ -936,8 +885,6 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>  
>  	pci_assign_unassigned_bus_resources(vmd->bus);
>  
> -	pci_walk_bus(vmd->bus, vmd_pm_enable_quirk, &features);
> -
>  	/*
>  	 * VMD root buses are virtual and don't return true on pci_is_pcie()
>  	 * and will fail pcie_bus_configure_settings() early. It can instead be
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 44cab813bf95..2d86623f96e3 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -6023,3 +6023,75 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a2d, dpc_log_size);
>  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a2f, dpc_log_size);
>  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a31, dpc_log_size);
>  #endif
> +
> +#ifdef CONFIG_VMD
> +/*
> + * Enable ASPM on the PCIE root ports under VMD and set the default LTR of the
> + * storage devices on platforms where these values are not configured by BIOS.
> + * This is needed for laptops, which require these settings for proper power
> + * management of the SoC.
> + */
> +#define VMD_DEVICE_LTR	0x1003	/* 3145728 ns */
> +static void quirk_intel_vmd(struct pci_dev *pdev)
> +{
> +	struct pci_dev *parent;
> +	u16 ltr = VMD_DEVICE_LTR;
> +	u32 ltr_reg;
> +	int pos;
> +
> +	/* Check in VMD domain */
> +	if (pci_domain_nr(pdev->bus) < 0x10000)
> +		return;
> +
> +	/* Get Root Port */
> +	parent = pci_upstream_bridge(pdev);
> +	if (!parent || parent->vendor != PCI_VENDOR_ID_INTEL)
> +		return;
> +
> +	/* Get VMD Host Bridge */
> +	parent = to_pci_dev(parent->dev.parent);
> +	if (!parent)
> +		return;
> +
> +	/* Get RAID controller */
> +	parent = to_pci_dev(parent->dev.parent);
> +	if (!parent)
> +		return;
> +
> +	switch (parent->device) {
> +	case 0x467f:
> +	case 0x4c3d:
> +	case 0xa77f:
> +	case 0x7d0b:
> +	case 0xad0b:
> +	case 0x9a0b:
> +		break;
> +	default:
> +		return;
> +	}
> +
> +	pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL);
> +
> +	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
> +	if (!pos)
> +		return;
> +
> +	/* Skip if the max snoop LTR is non-zero, indicating BIOS has set it */
> +	pci_read_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, &ltr_reg);
> +	if (!!(ltr_reg & (PCI_LTR_VALUE_MASK | PCI_LTR_SCALE_MASK)))
> +		return;
> +
> +	/*
> +	 * Set the LTR values to the maximum required by the platform to
> +	 * allow the deepest power management savings. Write as a DWORD where
> +	 * the lower word is the max snoop latency and the upper word is the
> +	 * max non-snoop latency.
> +	 */
> +	ltr_reg = (ltr << 16) | ltr;
> +	pci_write_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, ltr_reg);
> +	pci_info(pdev, "LTR set by VMD PCI quick\n");
> +
> +}
> +DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_ANY_ID, PCI_ANY_ID,
> +			      PCI_CLASS_STORAGE_EXPRESS, 0, quirk_intel_vmd);
> +#endif
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel