linux-kernel - Re: [PATCH v2 5/9] PCI: pciehp: Move check for is

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Message-ID: <e0a74b28-e862-202e-328-9eca3cb622f@linux.intel.com>
Date:   Mon, 6 Nov 2023 14:41:58 +0200 (EET)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Mario Limonciello <mario.limonciello@....com>
cc:     Karol Herbst <kherbst@...hat.com>, Lyude Paul <lyude@...hat.com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Lukas Wunner <lukas@...ner.de>,
        Danilo Krummrich <dakr@...hat.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Xinhui Pan <Xinhui.Pan@....com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Mark Gross <markgross@...nel.org>,
        Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        Pali Rohár <pali@...nel.org>,
        Marek Behún <kabel@...nel.org>,
        "Maciej W . Rozycki" <macro@...am.me.uk>,
        Manivannan Sadhasivam <mani@...nel.org>,
        "open list:DRM DRIVER FOR NVIDIA GEFORCE/QUADRO GPUS" 
        <dri-devel@...ts.freedesktop.org>,
        "open list:DRM DRIVER FOR NVIDIA GEFORCE/QUADRO GPUS" 
        <nouveau@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:RADEON and AMDGPU DRM DRIVERS" 
        <amd-gfx@...ts.freedesktop.org>,
        "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
        "open list:ACPI" <linux-acpi@...r.kernel.org>,
        "open list:X86 PLATFORM DRIVERS" 
        <platform-driver-x86@...r.kernel.org>,
        "open list:THUNDERBOLT DRIVER" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v2 5/9] PCI: pciehp: Move check for is_thunderbolt into
 a quirk

On Fri, 3 Nov 2023, Mario Limonciello wrote:

> commit 493fb50e958c ("PCI: pciehp: Assume NoCompl+ for Thunderbolt
> ports") added a check into pciehp code to explicitly set NoCompl+
> for all Intel Thunderbolt controllers, including those that don't
> need it.
> 
> This overloaded the purpose of the `is_thunderbolt` member of
> `struct pci_device` because that means that any controller that
> identifies as thunderbolt would set NoCompl+ even if it doesn't
> suffer this deficiency. As that commit helpfully specifies all the
> controllers with the problem, move them into a PCI quirk.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>  drivers/pci/hotplug/pciehp_hpc.c |  6 +-----
>  drivers/pci/quirks.c             | 20 ++++++++++++++++++++
>  include/linux/pci.h              |  1 +
>  3 files changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index fd713abdfb9f..23a92d681d1c 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -991,11 +991,7 @@ 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_command_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 eeec1d6f9023..4bbf6e33ca11 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3807,6 +3807,26 @@ 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);
>  
> +/*
> + * We assume no Thunderbolt controllers support Command Complete events,
> + * but some controllers falsely claim they do.

IMO, this wording makes little sense with the new code. How about taking 
some text from the original commit's changelog:

/*
 * Certain Thunderbolt 1 controllers falsely claim to support Command 
 * Completed events.
 */

The code change looks fine.

-- 
 i.

> + */
> +static void quirk_thunderbolt_command_complete(struct pci_dev *pdev)
> +{
> +	pdev->no_command_complete = 1;
> +}
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_LIGHT_RIDGE,
> +			quirk_thunderbolt_command_complete);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_EAGLE_RIDGE,
> +			quirk_thunderbolt_command_complete);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_LIGHT_PEAK,
> +			quirk_thunderbolt_command_complete);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_CACTUS_RIDGE_4C,
> +			quirk_thunderbolt_command_complete);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_CACTUS_RIDGE_2C,
> +			quirk_thunderbolt_command_complete);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_PORT_RIDGE,
> +			quirk_thunderbolt_command_complete);
>  #ifdef CONFIG_ACPI
>  /*
>   * Apple: Shutdown Cactus Ridge Thunderbolt controller.
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 530b0a360514..439c2dac8a3e 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -441,6 +441,7 @@ 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_command_complete:1;	/* No command completion */
>  	/*
>  	 * Devices marked being untrusted are the ones that can potentially
>  	 * execute DMA attacks and similar. They are typically connected
>