linux-kernel - RE: [PATCH] pci: Add a few new IDs for Intel GPU "spurious interrupt" quirk

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Date:   Mon, 8 Oct 2018 10:06:40 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Bin Meng' <bmeng.cn@...il.com>,
        "helgaas@...nel.org" <helgaas@...nel.org>
CC:     Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Thomas Jarosch <thomas.jarosch@...ra2net.com>,
        stable <stable@...r.kernel.org>,
        "jani.nikula@...ux.intel.com" <jani.nikula@...ux.intel.com>,
        "joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>,
        "rodrigo.vivi@...el.com" <rodrigo.vivi@...el.com>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] pci: Add a few new IDs for Intel GPU "spurious interrupt"
 quirk

From: Bin Meng
> Sent: 08 October 2018 10:44
...
> Correct, disable the shared interrupt line keeps all devices using
> that line from working, which is current kernel's behavior w/o this
> quirk handling: it disables the (shared) interrupt line after 100.000+
> generated interrupts. But the side effect is that other devices become
> unusable after that (eg: USB devices which share the same interrupt
> line with the Intel GPU). That's why the original commit, f67fd55fa96f
> ("PCI: Add quirk for still enabled interrupts on Intel Sandy Bridge
> GPUs") disables the GPU's interrupt directly, which should really be
> done by the VGA BIOS itself (a buggy VBIOS!).

Shouldn't the kernel just disable all PCI(e) interrupts by writing
1 to the config space control register bit during grope?
Can it ever by right for this to be set?

Apart from VGA the 'bus master' bit also needs to be clear.

ISTR some very early PCI systems which failed to reset the PCI
bus during reboot - at least the 'bus master' bit remained
set for an ethernet card.
On a private LAN the OS got reinstalled and rebooted without
using all the ethernet receive buffers and then died because
a receive frame got written into 'random' memory.

	David

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