PCI/ACPI: Check for _OSC support in acpi_pci_osc_control_set()

Get rid of acpi_pci_osc_support() and check for _OSC supported features
directly in acpi_pci_osc_control_set(). There is no point in doing an
unconditional _OSC query with control=0 even when the kernel later wants to
take control over more features.

This saves one _OSC query and simplifies the code by getting rid of the
acpi_pci_osc_support() function. As a side effect, the !control checks in
acpi_pci_query_osc() can also be removed.

Link: https://lore.kernel.org/r/20210824122054.29481-5-joro@8bytes.org
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index f12e512..ab2f7df 100644 (file)
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -203,26 +203,16 @@ static acpi_status acpi_pci_query_osc(struct acpi_pci_root *root,
 
        capbuf[OSC_QUERY_DWORD] = OSC_QUERY_ENABLE;
        capbuf[OSC_SUPPORT_DWORD] = support;
-       if (control)
-               capbuf[OSC_CONTROL_DWORD] = *control | root->osc_control_set;
-       else
-               /* Run _OSC query only with existing controls. */
-               capbuf[OSC_CONTROL_DWORD] = root->osc_control_set;
+       capbuf[OSC_CONTROL_DWORD] = *control | root->osc_control_set;
 
        status = acpi_pci_run_osc(root->device->handle, capbuf, &result);
        if (ACPI_SUCCESS(status)) {
                root->osc_support_set = support;
-               if (control)
-                       *control = result;
+               *control = result;
        }
        return status;
 }
 
-static acpi_status acpi_pci_osc_support(struct acpi_pci_root *root, u32 flags)
-{
-       return acpi_pci_query_osc(root, flags, NULL);
-}
-
 struct acpi_pci_root *acpi_pci_find_root(acpi_handle handle)
 {
        struct acpi_pci_root *root;
@@ -345,8 +335,9 @@ EXPORT_SYMBOL_GPL(acpi_get_pci_dev);
  * _OSC bits the BIOS has granted control of, but its contents are meaningless
  * on failure.
  **/
-static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 req)
+static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 support)
 {
+       u32 req = OSC_PCI_EXPRESS_CAPABILITY_CONTROL;
        struct acpi_pci_root *root;
        acpi_status status;
        u32 ctrl, capbuf[3];
@@ -354,22 +345,16 @@ static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 r
        if (!mask)
                return AE_BAD_PARAMETER;
 
-       ctrl = *mask;
-       if ((ctrl & req) != req)
-               return AE_TYPE;
-
        root = acpi_pci_find_root(handle);
        if (!root)
                return AE_NOT_EXIST;
 
-       *mask = ctrl | root->osc_control_set;
-       /* No need to evaluate _OSC if the control was already granted. */
-       if ((root->osc_control_set & ctrl) == ctrl)
-               return AE_OK;
+       ctrl   = *mask;
+       *mask |= root->osc_control_set;
 
        /* Need to check the available controls bits before requesting them. */
-       while (*mask) {
-               status = acpi_pci_query_osc(root, root->osc_support_set, mask);
+       do {
+               status = acpi_pci_query_osc(root, support, mask);
                if (ACPI_FAILURE(status))
                        return status;
                if (ctrl == *mask)
@@ -377,7 +362,11 @@ static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 r
                decode_osc_control(root, "platform does not support",
                                   ctrl & ~(*mask));
                ctrl = *mask;
-       }
+       } while (*mask);
+
+       /* No need to request _OSC if the control was already granted. */
+       if ((root->osc_control_set & ctrl) == ctrl)
+               return AE_OK;
 
        if ((ctrl & req) != req) {
                decode_osc_control(root, "not requesting control; platform does not support",
@@ -470,7 +459,7 @@ static bool os_control_query_checks(struct acpi_pci_root *root, u32 support)
 static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
                                 bool is_pcie)
 {
-       u32 support, control, requested;
+       u32 support, control = 0, requested = 0;
        acpi_status status;
        struct acpi_device *device = root->device;
        acpi_handle handle = device->handle;
@@ -490,28 +479,15 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
        support = calculate_support();
 
        decode_osc_support(root, "OS supports", support);
-       status = acpi_pci_osc_support(root, support);
-       if (ACPI_FAILURE(status)) {
-               *no_aspm = 1;
-
-               /* _OSC is optional for PCI host bridges */
-               if ((status == AE_NOT_FOUND) && !is_pcie)
-                       return;
-
-               dev_info(&device->dev, "_OSC: platform retains control of PCIe features (%s)\n",
-                        acpi_format_exception(status));
-               return;
-       }
-
-       if (!os_control_query_checks(root, support))
-               return;
 
-       requested = control = calculate_control();
+       if (os_control_query_checks(root, support))
+               requested = control = calculate_control();
 
-       status = acpi_pci_osc_control_set(handle, &control,
-                                         OSC_PCI_EXPRESS_CAPABILITY_CONTROL);
+       status = acpi_pci_osc_control_set(handle, &control, support);
        if (ACPI_SUCCESS(status)) {
-               decode_osc_control(root, "OS now controls", control);
+               if (control)
+                       decode_osc_control(root, "OS now controls", control);
+
                if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
                        /*
                         * We have ASPM control, but the FADT indicates that
@@ -522,11 +498,6 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
                        *no_aspm = 1;
                }
        } else {
-               decode_osc_control(root, "OS requested", requested);
-               decode_osc_control(root, "platform willing to grant", control);
-               dev_info(&device->dev, "_OSC: platform retains control of PCIe features (%s)\n",
-                       acpi_format_exception(status));
-
                /*
                 * We want to disable ASPM here, but aspm_disabled
                 * needs to remain in its state from boot so that we
@@ -535,6 +506,18 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
                 * root scan.
                 */
                *no_aspm = 1;
+
+               /* _OSC is optional for PCI host bridges */
+               if ((status == AE_NOT_FOUND) && !is_pcie)
+                       return;
+
+               if (control) {
+                       decode_osc_control(root, "OS requested", requested);
+                       decode_osc_control(root, "platform willing to grant", control);
+               }
+
+               dev_info(&device->dev, "_OSC: platform retains control of PCIe features (%s)\n",
+                        acpi_format_exception(status));
        }
 }