linux-kernel - Re: [PATCH v3] PCI/portdrv: Allow AER service only for Root Ports & RCECs

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Date:   Mon, 12 Dec 2022 08:21:22 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v3] PCI/portdrv: Allow AER service only for Root Ports &
 RCECs

Hi Bjorn,

On Fri, Dec 09, 2022 at 06:29:22PM -0600, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@...gle.com>
> 
> Previously portdrv allowed the AER service for any device with an AER
> capability (assuming Linux had control of AER) even though the AER service
> driver only attaches to Root Port and RCECs.
> 
> Because get_port_device_capability() included AER for non-RP, non-RCEC
> devices, we tried to initialize the AER IRQ even though these devices
> don't generate AER interrupts.
> 
> Intel DG1 and DG2 discrete graphics cards contain a switch leading to a
> GPU.  The switch supports AER but not MSI, so initializing an AER IRQ
> failed, and portdrv failed to claim the switch port at all.  The GPU itself
> could be suspended, but the switch could not be put in a low-power state
> because it had no driver.
> 
> Don't allow the AER service on non-Root Port, non-Root Complex Event
> Collector devices.  This means we won't enable Bus Mastering if the device
> doesn't require MSI, the AER service will not appear in sysfs, and the AER
> service driver will not bind to the device.
> 
> Link: https://lore.kernel.org/r/20221207084105.84947-1-mika.westerberg@linux.intel.com
> Based-on-patch-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>

Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>

I asked our GPU folks to try this out too. Hoping to get some results
during the week.