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

Christopher Covington
2016-06-03T15:15:30Z

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?

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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