Re: [PATCH V6 0/5] ECAM quirks handling for ARM64 platforms

[Bjorn Helgaas]

On Tue, Sep 20, 2016 at 09:15:14PM -0400, cov@xxxxxxxxxxxxxx wrote:
> Hi Bjorn, Thomasz,
> 
> On 2016-09-20 15:26, Bjorn Helgaas wrote:
> >On Fri, Sep 09, 2016 at 09:24:02PM +0200, Tomasz Nowicki wrote:
> >>Quirk handling relies on an idea of simple static array which contains
> >>quirk enties. Each entry consists of identification information
> >>(IDs from
> >>standard header of MCFG table) along with custom pci_ecam_ops
> >>structure and
> >>configuration space resource structure. This way it is possible find
> >>corresponding quirk entries and override pci_ecam_ops and PCI
> >>configuration
> >>space regions.
> >>
> >>As an example, the last 3 patches present quirk handling
> >>mechanism usage for
> >>ThunderX.
> >>
> >>v5 -> v6
> >>- rebase against v4.8-rc5
> >>- drop patch 1 form previous series
> >>- keep pci_acpi_setup_ecam_mapping() in ARM64 arch directory
> >>- move quirk code to pci_mcfg.c
> >>- restrict quirk to override pci_ecam_ops and CFG resource structure
> >>  only, no init call any more
> >>- split ThunderX quirks into the smaller chunks
> >>- add ThunderX pass1.x silicon revision support
> >>
> >>v4 -> v5
> >>- rebase against v4.8-rc1
> >>- rework to exact MCFG OEM ID, TABLE ID, rev match
> >>  - use memcmp instead of strncmp
> >>  - no substring match
> >>- fix typos and dmesg message
> >>
> >>Tomasz Nowicki (5):
> >>  PCI/ACPI: Extend pci_mcfg_lookup() responsibilities
> >>  PCI/ACPI: Check platform specific ECAM quirks
> >>  PCI: thunder-pem: Allow to probe PEM-specific register range
> >>for ACPI
> >>    case
> >>  PCI: thunder: Enable ACPI PCI controller for ThunderX pass2.x
> >>silicon
> >>    version
> >>  PCI: thunder: Enable ACPI PCI controller for ThunderX pass1.x
> >>silicon
> >>    version
> >>
> >> arch/arm64/kernel/pci.c             |  17 ++--
> >> drivers/acpi/pci_mcfg.c             | 168
> >>+++++++++++++++++++++++++++++++++++-
> >> drivers/pci/host/pci-thunder-ecam.c |   2 +-
> >> drivers/pci/host/pci-thunder-pem.c  |  63 +++++++++++---
> >> include/linux/pci-acpi.h            |   4 +-
> >> include/linux/pci-ecam.h            |   7 ++
> >> 6 files changed, 230 insertions(+), 31 deletions(-)
> >
> >I'm not quite ready to merge these because we haven't resolved the
> >question of how to expose the resources used by the memory-mapped
> >config space.  I'm fine with the first two patches (I did make a
> >couple trivial changes, see below), but there's no point in merging
> >them until we merge a user for them.
> >
> >I pushed the series to pci/ecam-v6 for build testing and discussion.
> >The diff (the changes I made locally) from v6 as posted by Tomasz is
> >below.
> 
> Rebasing the following simple quirks framework user onto this branch,
> I have some questions.
> 
> https://source.codeaurora.org/quic/server/kernel/commit/?h=cov/4.8-rc2-testing&id=83b766cafef11c107b10177d0626db311f382299
> 
> >diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
> >index eb14f74..bb3b8ad 100644
> >--- a/drivers/acpi/pci_mcfg.c
> >+++ b/drivers/acpi/pci_mcfg.c
> >@@ -42,86 +42,59 @@ struct mcfg_fixup {
> > 	struct resource cfgres;
> > };
> >
> >-#define MCFG_DOM_ANY			(-1)
> 
> Did you delete this because there were no current users, because you'd
> prefer users just use "-1", or for some other reason?

I removed it because there were no users of it and, more importantly,
the code doesn't implement support for it.

> > #define MCFG_BUS_RANGE(start, end)	DEFINE_RES_NAMED((start),	\
> > 						((end) - (start) + 1),	\
> > 						NULL, IORESOURCE_BUS)
> >-#define MCFG_BUS_ANY		MCFG_BUS_RANGE(0x0, 0xff)
> >-#define MCFG_RES_EMPTY		DEFINE_RES_NAMED(0, 0, NULL, 0)
> >+#define MCFG_BUS_ANY			MCFG_BUS_RANGE(0x0, 0xff)
> >
> > static struct mcfg_fixup mcfg_quirks[] = {
> >-/*	{ OEM_ID, OEM_TABLE_ID, REV, DOMAIN, BUS_RANGE, cfgres, ops }, */
> >+/*	{ OEM_ID, OEM_TABLE_ID, REV, SEGMENT, BUS_RANGE, cfgres, ops }, */
> 
> This comment appears to have the order of cfgres and ops reversed.

Fixed, thanks!

> Am I correct in reading that if a user of the framework does not wish to
> override cfgres they must place a struct resource with .start = 0 at the
> end of their mcfg_quirks entry? If so, I guess I have the same questions
> about removing MCFG_RES_EMPTY as I do about removing MCFG_DOM_ANY.

You're right that we only override cfgres if the quirk supplies a
struct resource with non-zero .start.  I removed MCFG_RES_EMPTY
because mcfg_quirks[] is a static array and is initialized with all
members being zero anyway.  If a quirk doesn't need to override
cfgres, I think it's more readable if the quirk just doesn't mention
the resource at all.

Bjorn