On Thu, Mar 27, 2025 at 7:57 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
>
> On Thu, Mar 13, 2025 at 11:07 AM Zhou Shengqing
> <zhoushengqing@xxxxxxxxxxx> wrote:
> >
> > Per PCI Firmware Specification Revision 3.3 Table 4-7 _DSM Definitions
> > for PCI. Preserve PCI Boot Configuration Initial Revision ID changed to 2.
> >
> > And add acpi_check_dsm() for DSM_PCI_PRESERVE_BOOT_CONFIG.
> >
> > Signed-off-by: Zhou Shengqing <zhoushengqing@xxxxxxxxxxx>
> > ---
> > v5:follow Bjorn advice, add acpi_check_dsm for PCI _DSM.
> > v4:Initialize *obj to NULL.
> > v3:try revision id 1 first, then try revision id 2.
> > v2:add Fixes tag.
> >
> > Fixes: 9d7d5db8e78e ("PCI: Move PRESERVE_BOOT_CONFIG _DSM evaluation to pci_re")
> > ---
> > drivers/pci/pci-acpi.c | 43 ++++++++++++++++++++++++++++++------------
> > 1 file changed, 31 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> > index af370628e583..4f9e0548c96d 100644
> > --- a/drivers/pci/pci-acpi.c
> > +++ b/drivers/pci/pci-acpi.c
> > @@ -122,24 +122,43 @@ phys_addr_t acpi_pci_root_get_mcfg_addr(acpi_handle handle)
> >
> > bool pci_acpi_preserve_config(struct pci_host_bridge *host_bridge)
> > {
> > - if (ACPI_HANDLE(&host_bridge->dev)) {
> > - union acpi_object *obj;
> > + bool rc = false;
> > + union acpi_object *obj;
>
> + u64 rev;
>
> >
> > - /*
> > - * Evaluate the "PCI Boot Configuration" _DSM Function. If it
> > - * exists and returns 0, we must preserve any PCI resource
> > - * assignments made by firmware for this host bridge.
> > - */
> > + if (!ACPI_HANDLE(&host_bridge->dev))
> > + return false;
> > +
> > + /*
> > + * Evaluate the "PCI Boot Configuration" _DSM Function. If it
> > + * exists and returns 0, we must preserve any PCI resource
> > + * assignments made by firmware for this host bridge.
> > + *
> > + * Per PCI Firmware r3.2, released Jan 26, 2015,
> > + * DSM_PCI_PRESERVE_BOOT_CONFIG Revision ID is 1. But PCI Firmware r3.3,
> > + * released Jan 20, 2021, changed sec 4.6.5 to say
> > + * "lowest valid Revision ID value: 2". So check rev 1 first, then rev 2.
> > + */
>
> + for (rev = 1; rev <= 2; rev++) {
> + if (!acpi_check_dsm(ACPI_HANDLE(&host_bridge->dev),
> &pci_acpi_dsm_guid,
> + rev, BIT(DSM_PCI_PRESERVE_BOOT_CONFIG)))
> + continue;
> +
> + obj =
> acpi_evaluate_dsm_typed(ACPI_HANDLE(&host_bridge->dev), ,
> &pci_acpi_dsm_guid,
> + rev, BIT(DSM_PCI_PRESERVE_BOOT_CONFIG));
Of course, the above acpi_evaluate_dsm_typed() call has been
messed-up, it should be
obj = acpi_evaluate_dsm_typed(ACPI_HANDLE(&host_bridge->dev),
&pci_acpi_dsm_guid, rev,
DSM_PCI_PRESERVE_BOOT_CONFIG,
NULL, ACPI_TYPE_INTEGER);
but the idea should be clear nevertheless.
> + if (obj && obj->integer.value == 0)
> + rc = true;
> +
> + ACPI_FREE(obj);
> +
> + if (rc)
> + return true;
> + }
> +
> + return false;
>
> would achieve the same with fewer lines of code and less code
> duplication if I'm not mistaken.
>
> > + if (acpi_check_dsm(ACPI_HANDLE(&host_bridge->dev),
> > + &pci_acpi_dsm_guid, 1, BIT(DSM_PCI_PRESERVE_BOOT_CONFIG))) {
> > obj = acpi_evaluate_dsm_typed(ACPI_HANDLE(&host_bridge->dev),
> > - &pci_acpi_dsm_guid,
> > - 1, DSM_PCI_PRESERVE_BOOT_CONFIG,
> > - NULL, ACPI_TYPE_INTEGER);
> > + &pci_acpi_dsm_guid,
> > + 1, DSM_PCI_PRESERVE_BOOT_CONFIG,
> > + NULL, ACPI_TYPE_INTEGER);
> > if (obj && obj->integer.value == 0)
> > - return true;
> > + rc = true;
> > + ACPI_FREE(obj);
> > + } else if (acpi_check_dsm(ACPI_HANDLE(&host_bridge->dev),
> > + &pci_acpi_dsm_guid, 2, BIT(DSM_PCI_PRESERVE_BOOT_CONFIG))) {
> > + obj = acpi_evaluate_dsm_typed(ACPI_HANDLE(&host_bridge->dev),
> > + &pci_acpi_dsm_guid,
> > + 2, DSM_PCI_PRESERVE_BOOT_CONFIG,
> > + NULL, ACPI_TYPE_INTEGER);
> > + if (obj && obj->integer.value == 0)
> > + rc = true;
> > ACPI_FREE(obj);
> > }
> >
> > - return false;
> > + return rc;
> > }
> >
> > /* _HPX PCI Setting Record (Type 0); same as _HPP */
> > --
