RE: [RFC PATCH 1/3] pci, acpi: Match PCI config space accessors against platfrom specific ECAM quirks.

Gabriele Paoloni
2016-06-06T07:28:14Z

Hi Jeffrey

> -----Original Message-----
> From: Jeffrey Hugo [mailto:jhugo@codeaurora.org]
> Sent: 03 June 2016 18:00
> To: Gabriele Paoloni; Christopher Covington; Tomasz Nowicki;
> helgaas@kernel.org; arnd@arndb.de; will.deacon@arm.com;
> catalin.marinas@arm.com; rafael@kernel.org; hanjun.guo@linaro.org;
> Lorenzo.Pieralisi@arm.com; okaya@codeaurora.org; jchandra@broadcom.com
> Cc: liudongdong (C); linaro-acpi@lists.linaro.org; jcm@redhat.com;
> dhdang@apm.com; Liviu.Dudau@arm.com; ddaney@caviumnetworks.com;
> jeremy.linton@arm.com; linux-kernel@vger.kernel.org; linux-
> acpi@vger.kernel.org; robert.richter@caviumnetworks.com;
> msalter@redhat.com; Suravee.Suthikulpanit@amd.com; linux-
> pci@vger.kernel.org; Wangyijing; mw@semihalf.com;
> andrea.gallo@linaro.org; linux-arm-kernel@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@vger.kernel.org [mailto:linux-pci-
> >> owner@vger.kernel.org] On Behalf Of Christopher Covington
> >> Sent: 03 June 2016 16:15
> >> To: Tomasz Nowicki; helgaas@kernel.org; arnd@arndb.de;
> >> will.deacon@arm.com; catalin.marinas@arm.com; rafael@kernel.org;
> >> hanjun.guo@linaro.org; Lorenzo.Pieralisi@arm.com;
> okaya@codeaurora.org;
> >> jchandra@broadcom.com
> >> Cc: jcm@redhat.com; linaro-acpi@lists.linaro.org; linux-
> >> pci@vger.kernel.org; dhdang@apm.com; Liviu.Dudau@arm.com;
> >> ddaney@caviumnetworks.com; jeremy.linton@arm.com; linux-
> >> kernel@vger.kernel.org; linux-acpi@vger.kernel.org;
> >> robert.richter@caviumnetworks.com; Suravee.Suthikulpanit@amd.com;
> >> msalter@redhat.com; Wangyijing; mw@semihalf.com;
> >> andrea.gallo@linaro.org; linux-arm-kernel@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 <tn@semihalf.com>
> >>> ---
> >>> 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
> >>
> >> --
> >> Qualcomm Innovation Center, Inc.
> >> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> >> a Linux Foundation Collaborative Project
> >> --
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> in
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> >
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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