[RFC PATCH 1/3] pci, acpi: Match PCI config space accessors against platfrom... | linux-arm-kernel

quoted

Hi Jeffrey

-----Original Message-----
From: Jeffrey Hugo [mailto:jhugo at codeaurora.org]
Sent: 03 June 2016 18:00
To: Gabriele Paoloni; Christopher Covington; Tomasz Nowicki;
helgaas at kernel.org; arnd at arndb.de; will.deacon at arm.com;
catalin.marinas at arm.com; rafael at kernel.org; hanjun.guo at linaro.org;
Lorenzo.Pieralisi at arm.com; okaya at codeaurora.org; jchandra at broadcom.com
Cc: liudongdong (C); linaro-acpi at lists.linaro.org; jcm at redhat.com;
dhdang at apm.com; Liviu.Dudau at arm.com; ddaney at caviumnetworks.com;
jeremy.linton at arm.com; linux-kernel at vger.kernel.org; linux-
acpi at vger.kernel.org; robert.richter at caviumnetworks.com;
msalter at redhat.com; Suravee.Suthikulpanit at amd.com; linux-
pci at vger.kernel.org; Wangyijing; mw at semihalf.com;
andrea.gallo at linaro.org; linux-arm-kernel at lists.infradead.org
Subject: Re: [RFC PATCH 1/3] pci, acpi: Match PCI config space
accessors against platfrom specific ECAM quirks.

On 6/3/2016 9:32 AM, Gabriele Paoloni wrote:
Hi Cov

-----Original Message-----
From: linux-pci-owner at vger.kernel.org [mailto:linux-pci-
owner at vger.kernel.org] On Behalf Of Christopher Covington
Sent: 03 June 2016 16:15
To: Tomasz Nowicki; helgaas at kernel.org; arnd at arndb.de;
will.deacon at arm.com; catalin.marinas at arm.com; rafael at kernel.org;
hanjun.guo at linaro.org; Lorenzo.Pieralisi at arm.com;
okaya at codeaurora.org;
jchandra at broadcom.com
Cc: jcm at redhat.com; linaro-acpi at lists.linaro.org; linux-
pci at vger.kernel.org; dhdang at apm.com; Liviu.Dudau at arm.com;
ddaney at caviumnetworks.com; jeremy.linton at arm.com; linux-
kernel at vger.kernel.org; linux-acpi at vger.kernel.org;
robert.richter at caviumnetworks.com; Suravee.Suthikulpanit at amd.com;
msalter at redhat.com; Wangyijing; mw at semihalf.com;
andrea.gallo at linaro.org; linux-arm-kernel at lists.infradead.org;
liudongdong (C); Gabriele Paoloni
Subject: Re: [RFC PATCH 1/3] pci, acpi: Match PCI config space
accessors against platfrom specific ECAM quirks.

Hi Tomasz,

Thanks for your work on this.

On 06/02/2016 04:41 AM, 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. Algorithm traverses available quirk list, matches against
<oem_id, oem_rev, domain, bus number> tuple and returns
corresponding
PCI config ops. oem_id and oem_rev come from MCFG table standard
header.
All quirks can be defined using DECLARE_ACPI_MCFG_FIXUP() macro and
kept self contained. Example:

/* Custom PCI config ops */
static struct pci_generic_ecam_ops foo_pci_ops = {
	.bus_shift	= 24,
	.pci_ops = {
		.map_bus = pci_ecam_map_bus,
		.read = foo_ecam_config_read,
		.write = foo_ecam_config_write,
	}
};

DECLARE_ACPI_MCFG_FIXUP(&foo_pci_ops, <oem_id_str>, <oem_rev>,
<domain_nr>, <bus_nr>);
Signed-off-by: Tomasz Nowicki <redacted>
---
 drivers/acpi/pci_mcfg.c           | 32
++++++++++++++++++++++++++++++++
 include/asm-generic/vmlinux.lds.h |  7 +++++++
 include/linux/pci-acpi.h          | 19 +++++++++++++++++++
 3 files changed, 58 insertions(+)

diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
index 1847f74..f3d4570 100644
--- a/drivers/acpi/pci_mcfg.c
+++ b/drivers/acpi/pci_mcfg.c
@@ -22,11 +22,43 @@
 #include <linux/kernel.h>
 #include <linux/pci.h>
 #include <linux/pci-acpi.h>
+#include <linux/pci-ecam.h>

 /* Root pointer to the mapped MCFG table */
 static struct acpi_table_mcfg *mcfg_table;
 static int mcfg_entries;

+extern struct pci_cfg_fixup __start_acpi_mcfg_fixups[];
+extern struct pci_cfg_fixup __end_acpi_mcfg_fixups[];
+
+struct pci_ecam_ops *pci_mcfg_get_ops(struct acpi_pci_root *root)
+{
+	int bus_num = root->secondary.start;
+	int domain = root->segment;
+	struct pci_cfg_fixup *f;
+
+	if (!mcfg_table)
+		return &pci_generic_ecam_ops;
+
+	/*
+	 * Match against platform specific quirks and return
corresponding
+	 * CAM ops.
+	 *
+	 * First match against PCI topology <domain:bus> then use OEM ID
and
+	 * OEM revision from MCFG table standard header.
+	 */
+	for (f = __start_acpi_mcfg_fixups; f < __end_acpi_mcfg_fixups;
f++) {
+		if ((f->domain == domain || f->domain ==
PCI_MCFG_DOMAIN_ANY) &&
+		    (f->bus_num == bus_num || f->bus_num ==
PCI_MCFG_BUS_ANY) &&
+		    (!strncmp(f->oem_id, mcfg_table->header.oem_id,
+			      ACPI_OEM_ID_SIZE)) &&
+		    (f->oem_revision == mcfg_table->header.oem_revision))
Is this more likely to be updated between quirky and fixed platforms
than oem_table_id? What do folks think about using oem_table_id
instead
of, or in addition to, oem_revision?
From my understanding we need to stick to this mechanism as
(otherwise)
there are platforms out in the field that would need a FW update.

So I don't think that using oem_table_id "instead" is possible; about
"in addition" I think it is doable, but I do not see the advantage
much.
I mean that if a platform gets fixed the oem revision should change
too,
Right?
Cov and I had a discussion about this, so hopefully I can bring a
slightly different perspective that will make sense.

We forsee a situation where we have platform A that needs a quirk, and
platform B that does not.  The OEM id is the same for both platforms as
they are different platforms from the same OEM.  Using the OEM revision
field does not seem to be appropriate since these are different
platforms and the revision field appears to be for the purpose of
tracking differences within a single platform.  Therefore, Cov is
proposing using the OEM table id as a mechanism to distinguish platform
A (needs quirk applied) vs platform B (no quirks) from the same OEM.
Ah yes I see now...

Probably it should be ok to have a check on all three OEM fields.

Thanks for explaining

Gab 


Thanks

Gab

In case these details are helpful, here was my simple prototype of
an
MCFG based approach:

https://codeaurora.org/cgit/quic/server/kernel/commit/?h=cov/4.7-
rc1-
testing&id=c5d8bc49a198fd8f61f82c7d8f169564d6176b07
https://codeaurora.org/cgit/quic/server/kernel/commit/?h=cov/4.7-
rc1-
testing&id=50bfe77ccd1639e6ce8c7c4fcca187d50e0bead4

Thanks,
Cov

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--
Jeffrey Hugo
Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project

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