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>

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;
@@ -345,39 +335,38 @@ 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];
 
 	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)
 			break;
 		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));
 	}
 }