Re: [PATCH V2 22/23] pci, acpi: Match PCI config space accessors against platfrom specific quirks.
From: Jeremy Linton
Date: Fri Jan 08 2016 - 09:43:12 EST
On 01/08/2016 08:16 AM, Mark Salter wrote:
On Wed, 2015-12-16 at 16:16 +0100, Tomasz Nowicki wrote:
Some platforms may not be fully compliant with generic set of PCI config
accessors. For these cases we implement the way to overwrite accessors
set before PCI buses enumeration. Algorithm that overwrite accessors
matches against platform ID (DMI), domain and bus number, hopefully
enough for all cases. All quirks can be defined using:
DECLARE_ACPI_MCFG_FIXUP() and keep self contained.
...
This seems awkward to me in the case where the quirk is SoC-based and there
may be multiple platforms affected. Needing a DECLARE_ACPI_MCFG_FIXUP for
each platform using such a SoC (i.e. Mustang and Moonshot) doesn't seem
right. In that case, I think it'd be better to check CPUID and possibly
some SoC register to cover all platforms affected.
Also, there doesn't seem to be a way to connect a given quirk check to the
MCFG/device requesting the ops. So if there is a platform with multiple PCIE
roots and not all of them have quirks, how does one no whether to override the
default ecam ops?
That was the thinking that lead me to quirk the xgene based m400 using
the root bridge VID/DID and DECLARE_PCI_FIXUP_EARLY(). A solution which
works because the default config space accessors work sufficiently to
read the VID/DID.
I think that solution might work for at least one other vendor as well,
and IMHO is better than using DMI for the reasons you list.
I will rebase/post those patches RSN...
(please ignore the message below, i'm working getting that taken care of
as well)
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