drm/nouveau/acpi: check for function 0x1B before using it

commit cba97805 upstream.

Do not unconditionally invoke function 0x1B without checking for its
availability, it leads to an infinite loop on some firmware.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=104791
Fixes: 5addcf0a ("nouveau: add runtime PM support (v0.9)")
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Peter Wu <peter@lekensteyn.nl>
Acked-by: Dave Airlie <airlied@redhat.com
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpu/drm/nouveau/nouveau_acpi.c

@@ -45,6 +45,7 @@
 static struct nouveau_dsm_priv {
 	bool dsm_detected;
 	bool optimus_detected;
+	bool optimus_flags_detected;
 	acpi_handle dhandle;
 	acpi_handle other_handle;
 	acpi_handle rom_handle;
@@ -213,7 +214,8 @@ static struct vga_switcheroo_handler nouveau_dsm_handler = {
 };
 
 static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out,
-				  bool *has_mux, bool *has_opt)
+				  bool *has_mux, bool *has_opt,
+				  bool *has_opt_flags)
 {
 	acpi_handle dhandle;
 	bool supports_mux;
@@ -238,6 +240,7 @@ static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out
 	*dhandle_out = dhandle;
 	*has_mux = supports_mux;
 	*has_opt = !!optimus_funcs;
+	*has_opt_flags = optimus_funcs & (1 << NOUVEAU_DSM_OPTIMUS_FLAGS);
 
 	if (optimus_funcs) {
 		uint32_t result;
@@ -258,6 +261,7 @@ static bool nouveau_dsm_detect(void)
 	acpi_handle dhandle = NULL;
 	bool has_mux = false;
 	bool has_optimus = false;
+	bool has_optimus_flags = false;
 	int vga_count = 0;
 	bool guid_valid;
 	bool ret = false;
@@ -272,13 +276,15 @@ static bool nouveau_dsm_detect(void)
 	while ((pdev = pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, pdev)) != NULL) {
 		vga_count++;
 
-		nouveau_dsm_pci_probe(pdev, &dhandle, &has_mux, &has_optimus);
+		nouveau_dsm_pci_probe(pdev, &dhandle, &has_mux, &has_optimus,
+				      &has_optimus_flags);
 	}
 
 	while ((pdev = pci_get_class(PCI_CLASS_DISPLAY_3D << 8, pdev)) != NULL) {
 		vga_count++;
 
-		nouveau_dsm_pci_probe(pdev, &dhandle, &has_mux, &has_optimus);
+		nouveau_dsm_pci_probe(pdev, &dhandle, &has_mux, &has_optimus,
+				      &has_optimus_flags);
 	}
 
 	/* find the optimus DSM or the old v1 DSM */
@@ -289,6 +295,7 @@ static bool nouveau_dsm_detect(void)
 		printk(KERN_INFO "VGA switcheroo: detected Optimus DSM method %s handle\n",
 			acpi_method_name);
 		nouveau_dsm_priv.optimus_detected = true;
+		nouveau_dsm_priv.optimus_flags_detected = has_optimus_flags;
 		ret = true;
 	} else if (vga_count == 2 && has_mux && guid_valid) {
 		nouveau_dsm_priv.dhandle = dhandle;
@@ -332,8 +339,9 @@ void nouveau_switcheroo_optimus_dsm(void)
 	if (!nouveau_dsm_priv.optimus_detected)
 		return;
 
-	nouveau_optimus_dsm(nouveau_dsm_priv.dhandle, NOUVEAU_DSM_OPTIMUS_FLAGS,
-			    0x3, &result);
+	if (nouveau_dsm_priv.optimus_flags_detected)
+		nouveau_optimus_dsm(nouveau_dsm_priv.dhandle, NOUVEAU_DSM_OPTIMUS_FLAGS,
+				    0x3, &result);
 
 	nouveau_optimus_dsm(nouveau_dsm_priv.dhandle, NOUVEAU_DSM_OPTIMUS_CAPS,
 		NOUVEAU_DSM_OPTIMUS_SET_POWERDOWN, &result);