Re: [PATCH v3 02/12] PCI: Move `is_thunderbolt` check for lack of command completed to a quirk

[Bjorn Helgaas <helgaas@kernel.org>]

Update subject to something like:

  PCI: pciehp: Quirk broken Command Completed support on Intel Thunderbolt controllers

On Fri, Feb 11, 2022 at 01:32:40PM -0600, Mario Limonciello wrote:
> The `is_thunderbolt` check is currently used to indicate the lack of
> command completed support for a number of older Thunderbolt devices.
> 
> This however is heavy handed and should have been done via a quirk.  Move
> the affected devices outlined in commit 493fb50e958c ("PCI: pciehp: Assume
> NoCompl+ for Thunderbolt ports") into pci quirks.
> 
> Suggested-by: Lukas Wunner <lukas@wunner.de>
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>  drivers/pci/hotplug/pciehp_hpc.c |  6 +-----
>  drivers/pci/quirks.c             | 17 +++++++++++++++++
>  include/linux/pci.h              |  2 ++
>  3 files changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 1c1ebf3dad43..e4c42b24aba8 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -996,11 +996,7 @@ struct controller *pcie_init(struct pcie_device *dev)
>  	if (pdev->hotplug_user_indicators)
>  		slot_cap &= ~(PCI_EXP_SLTCAP_AIP | PCI_EXP_SLTCAP_PIP);
>  
> -	/*
> -	 * We assume no Thunderbolt controllers support Command Complete events,
> -	 * but some controllers falsely claim they do.
> -	 */
> -	if (pdev->is_thunderbolt)
> +	if (pdev->no_cmd_complete)
>  		slot_cap |= PCI_EXP_SLTCAP_NCCS;
>  
>  	ctrl->slot_cap = slot_cap;
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index d2dd6a6cda60..6d3c88edde00 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3675,6 +3675,23 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_CACTUS_RIDGE_4C
>  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_PORT_RIDGE,
>  			quirk_thunderbolt_hotplug_msi);

Please add a comment above to the effect that PCI_EXP_SLTCAP_NCCS
being clear means the controller generates a Command Completed software
notification when it completes a command, and these controllers don't
generate those notifications even though PCI_EXP_SLTCAP_NCCS is clear
(PCIe r6.0, sec 7.5.3.9).

> +static void quirk_thunderbolt_command_completed(struct pci_dev *pdev)

Rename to quirk_no_command_completed().  This doesn't have anything to
do with Thunderbolt; it's just that the affected devices happen to be
Thunderbolt controllers.

> +{
> +	pdev->no_cmd_complete = 1;
> +}
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_LIGHT_RIDGE,
> +			quirk_thunderbolt_command_completed);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_EAGLE_RIDGE,
> +			quirk_thunderbolt_command_completed);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_LIGHT_PEAK,
> +			quirk_thunderbolt_command_completed);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_CACTUS_RIDGE_4C,
> +			quirk_thunderbolt_command_completed);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_CACTUS_RIDGE_2C,
> +			quirk_thunderbolt_command_completed);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_PORT_RIDGE,
> +			quirk_thunderbolt_command_completed);

Can we put these in drivers/pci/hotplug/pciehp_hpc.c?  We already
have a few similar quirks there.

>  #ifdef CONFIG_ACPI
>  /*
>   * Apple: Shutdown Cactus Ridge Thunderbolt controller.
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 8253a5413d7c..1e5b769e42fc 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -443,6 +443,8 @@ struct pci_dev {
>  	unsigned int	is_hotplug_bridge:1;
>  	unsigned int	shpc_managed:1;		/* SHPC owned by shpchp */
>  	unsigned int	is_thunderbolt:1;	/* Thunderbolt controller */
> +	unsigned int	no_cmd_complete:1;	/* Lies about command completed events */
> +
>  	/*
>  	 * Devices marked being untrusted are the ones that can potentially
>  	 * execute DMA attacks and similar. They are typically connected
> -- 
> 2.34.1
>