From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Alex Williamson <alex.williamson@redhat.com>,
Bjorn Helgaas <helgaas@kernel.org>
Cc: Gabriele Paoloni <gabriele.paoloni@huawei.com>,
Daniel Axtens <dja@axtens.net>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"Liuxinliang (Matthew Liu)" <z.liuxinliang@hisilicon.com>,
Rongrong Zou <zourongrong@gmail.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
David Airlie <airlied@linux.ie>,
Daniel Vetter <daniel.vetter@intel.com>
Subject: Re: [PATCH v4] PCI: Support hibmc VGA cards behind a misbehaving HiSilicon bridge
Date: Fri, 14 Jul 2017 07:21:22 +1000 [thread overview]
Message-ID: <1499980882.2865.65.camel@kernel.crashing.org> (raw)
In-Reply-To: <20170713151146.53e9644c@w520.home>
On Thu, 2017-07-13 at 15:11 -0600, Alex Williamson wrote:
> > > */
> > > - if (vga_default == NULL &&
> > > - ((vgadev->owns & VGA_RSRC_LEGACY_MASK) == VGA_RSRC_LEGACY_MASK)) {
> > > + if (vga_default == NULL) {
> > > vgaarb_info(&pdev->dev, "setting as boot VGA device\n");
> > > vga_set_default_device(pdev);
> > > }
>
>
> "Legacy" is the breadcrumb we use to try to pick the same device for
> default VGA as the system firmware used as the boot VGA. There can be
> multiple VGA devices in the system, the change above would simply make
> the first discovered device be the default VGA. That would break many,
> many systems. If legacy VGA ranges mean nothing on ARM64, then follow
> the powerpc lead and make an arch quirk that simply selects the first
> enabled VGA device as the default. VGA routing is part of the PCI spec
> though, so the default of selecting the device with routing enabled
> makes sense. Thanks,
"Legacy" there iirc also means that it has decoding enabled at boot. If
you pick the first one you may pick a device that doesn't and hasn't
been initialized by any driver (good old BIOS-initialized text mode).
Cheers,
Ben.
WARNING: multiple messages have this Message-ID (diff)
From: benh@kernel.crashing.org (Benjamin Herrenschmidt)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4] PCI: Support hibmc VGA cards behind a misbehaving HiSilicon bridge
Date: Fri, 14 Jul 2017 07:21:22 +1000 [thread overview]
Message-ID: <1499980882.2865.65.camel@kernel.crashing.org> (raw)
In-Reply-To: <20170713151146.53e9644c@w520.home>
On Thu, 2017-07-13 at 15:11 -0600, Alex Williamson wrote:
> > > ????? */
> > > -???if (vga_default == NULL &&
> > > -?????? ((vgadev->owns & VGA_RSRC_LEGACY_MASK) == VGA_RSRC_LEGACY_MASK)) {
> > > +???if (vga_default == NULL) {
> > > ?????????????vgaarb_info(&pdev->dev, "setting as boot VGA device\n");
> > > ?????????????vga_set_default_device(pdev);
> > > ?????}?
>
>
> "Legacy" is the breadcrumb we use to try to pick the same device for
> default VGA as the system firmware used as the boot VGA.? There can be
> multiple VGA devices in the system, the change above would simply make
> the first discovered device be the default VGA.? That would break many,
> many systems.? If legacy VGA ranges mean nothing on ARM64, then follow
> the powerpc lead and make an arch quirk that simply selects the first
> enabled VGA device as the default.? VGA routing is part of the PCI spec
> though, so the default of selecting the device with routing enabled
> makes sense.? Thanks,
"Legacy" there iirc also means that it has decoding enabled at boot. If
you pick the first one you may pick a device that doesn't and hasn't
been initialized by any driver (good old BIOS-initialized text mode).
Cheers,
Ben.
next prev parent reply other threads:[~2017-07-13 21:21 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-12 5:08 [PATCH v4] PCI: Support hibmc VGA cards behind a misbehaving HiSilicon bridge Daniel Axtens
2017-07-12 20:04 ` Bjorn Helgaas
2017-07-12 20:04 ` Bjorn Helgaas
2017-07-13 10:29 ` Gabriele Paoloni
2017-07-13 10:29 ` Gabriele Paoloni
2017-07-13 11:29 ` Bjorn Helgaas
2017-07-13 11:29 ` Bjorn Helgaas
2017-07-13 20:45 ` Benjamin Herrenschmidt
2017-07-13 20:45 ` Benjamin Herrenschmidt
2017-07-14 12:14 ` Gabriele Paoloni
2017-07-14 12:14 ` Gabriele Paoloni
2017-07-13 21:11 ` Alex Williamson
2017-07-13 21:11 ` Alex Williamson
2017-07-13 21:21 ` Benjamin Herrenschmidt [this message]
2017-07-13 21:21 ` Benjamin Herrenschmidt
2017-07-14 12:26 ` Gabriele Paoloni
2017-07-14 12:26 ` Gabriele Paoloni
2017-07-14 13:50 ` Benjamin Herrenschmidt
2017-07-14 13:50 ` Benjamin Herrenschmidt
2017-07-14 17:03 ` Gabriele Paoloni
2017-07-14 17:03 ` Gabriele Paoloni
2017-07-14 23:54 ` Benjamin Herrenschmidt
2017-07-14 23:54 ` Benjamin Herrenschmidt
2017-07-14 14:43 ` Alex Williamson
2017-07-14 14:43 ` Alex Williamson
2017-07-14 1:35 ` Will Deacon
2017-07-14 1:35 ` Will Deacon
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