Re: [PATCH V3 13/21] pci, acpi: Provide generic way to assign bus domain number.

[Lorenzo Pieralisi]

Hi Tomasz,

On Wed, Jan 13, 2016 at 02:20:59PM +0100, Tomasz Nowicki wrote:

[...]

> @@ -4796,14 +4797,34 @@ void pci_bus_assign_domain_nr(struct pci_bus *bus, 
> struct device *parent)
>        * API and update the use_dt_domains value to keep track of method we
>        * are using to assign domain numbers (use_dt_domains = 0).
>        *
> +      * IF ACPI, we expect non-DT method (use_dt_domains == -1)
> +      * and call _SEG method for corresponding host bridge device.
> +      * If _SEG method does not exist, following ACPI spec (6.5.6)
> +      * all PCI buses belong to domain 0.
> +      *
>        * All other combinations imply we have a platform that is trying
> -      * to mix domain numbers obtained from DT and pci_get_new_domain_nr(),
> -      * which is a recipe for domain mishandling and it is prevented by
> -      * invalidating the domain value (domain = -1) and printing a
> -      * corresponding error.
> +      * to mix domain numbers obtained from DT, ACPI and
> +      * pci_get_new_domain_nr(), which is a recipe for domain mishandling and
> +      * it is prevented by invalidating the domain value (domain = -1) and
> +      * printing a corresponding error.
>        */
> +
>       if (domain >= 0 && use_dt_domains) {
>               use_dt_domains = 1;
> +#ifdef CONFIG_ACPI
> +     } else if (!acpi_disabled && use_dt_domains == -1) {
> +             struct acpi_device *acpi_dev = to_acpi_device(parent);
> +             unsigned long long segment = 0;
> +             acpi_status status;
> +
> +             status = acpi_evaluate_integer(acpi_dev->handle,
> +                                            METHOD_NAME__SEG, NULL,
> +                                            &segment);
> +             if (ACPI_FAILURE(status) && status != AE_NOT_FOUND)
> +                     dev_err(&acpi_dev->dev,  "can't evaluate _SEG\n");
> +
> +             domain = segment;
> +#endif

I think you can reshuffle a bit the code to make it easier to follow.

How about this ? (on top of mainline, I just compiled it do not
take it verbatim):

-- >8 --
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index d1a7105..467a316 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -7,6 +7,7 @@
  *     Copyright 1997 -- 2000 Martin Mares <m...@ucw.cz>
  */
 
+#include <linux/acpi.h>
 #include <linux/kernel.h>
 #include <linux/delay.h>
 #include <linux/init.h>
@@ -4769,7 +4770,27 @@ int pci_get_new_domain_nr(void)
 }
 
 #ifdef CONFIG_PCI_DOMAINS_GENERIC
-void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
+/* Feel free to add this to drivers/acpi as a helper */
+#ifdef CONFIG_ACPI
+int pci_bus_acpi_domain_nr(struct device *parent)
+{
+       struct acpi_device *acpi_dev = to_acpi_device(parent);
+       unsigned long long segment = 0;
+       acpi_status status;
+
+       status = acpi_evaluate_integer(acpi_dev->handle,
+                                      METHOD_NAME__SEG, NULL,
+                                      &segment);
+       if (ACPI_FAILURE(status) && status != AE_NOT_FOUND)
+               dev_err(&acpi_dev->dev,  "can't evaluate _SEG\n");
+
+       return segment;
+}
+#else
+int pci_bus_acpi_domain_nr(struct device *parent) { return -1; }
+#endif
+
+int pci_bus_of_domain_nr(struct device *parent)
 {
        static int use_dt_domains = -1;
        int domain = of_get_pci_domain_nr(parent->of_node);
@@ -4811,7 +4832,13 @@ void pci_bus_assign_domain_nr(struct pci_bus *bus, 
struct device *parent)
                domain = -1;
        }
 
-       bus->domain_nr = domain;
+       return domain;
+}
+
+void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
+{
+       bus->domain_nr = acpi_disabled ? pci_bus_of_domain_nr(parent) :
+                                        pci_bus_acpi_domain_nr(parent);
 }
 #endif
 #endif