vgaarb: Use ACPI HID name to find integrated GPU

Commit 3d42f1ddc47a ("vgaarb: Keep adding VGA device in queue") assumes
the first device is an integrated GPU. However, on AMD platforms an
integrated GPU can have higher PCI device number than a discrete GPU.

Integrated GPU on ACPI platform generally has _DOD and _DOS method, so
use that as predicate to find integrated GPU. If the new strategy
doesn't work, fallback to use the first device as boot VGA.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210519135723.525997-1-kai.heng.feng@canonical.com

diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index 5180c56..949fde4 100644 (file)
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -50,6 +50,7 @@
 #include <linux/screen_info.h>
 #include <linux/vt.h>
 #include <linux/console.h>
+#include <linux/acpi.h>
 
 #include <linux/uaccess.h>
 
@@ -1450,9 +1451,23 @@ static struct miscdevice vga_arb_device = {
        MISC_DYNAMIC_MINOR, "vga_arbiter", &vga_arb_device_fops
 };
 
+#if defined(CONFIG_ACPI)
+static bool vga_arb_integrated_gpu(struct device *dev)
+{
+       struct acpi_device *adev = ACPI_COMPANION(dev);
+
+       return adev && !strcmp(acpi_device_hid(adev), ACPI_VIDEO_HID);
+}
+#else
+static bool vga_arb_integrated_gpu(struct device *dev)
+{
+       return false;
+}
+#endif
+
 static void __init vga_arb_select_default_device(void)
 {
-       struct pci_dev *pdev;
+       struct pci_dev *pdev, *found = NULL;
        struct vga_device *vgadev;
 
 #if defined(CONFIG_X86) || defined(CONFIG_IA64)
@@ -1505,20 +1520,26 @@ static void __init vga_arb_select_default_device(void)
 #endif
 
        if (!vga_default_device()) {
-               list_for_each_entry(vgadev, &vga_list, list) {
+               list_for_each_entry_reverse(vgadev, &vga_list, list) {
                        struct device *dev = &vgadev->pdev->dev;
                        u16 cmd;
 
                        pdev = vgadev->pdev;
                        pci_read_config_word(pdev, PCI_COMMAND, &cmd);
                        if (cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) {
-                               vgaarb_info(dev, "setting as boot device (VGA legacy resources not available)\n");
-                               vga_set_default_device(pdev);
-                               break;
+                               found = pdev;
+                               if (vga_arb_integrated_gpu(dev))
+                                       break;
                        }
                }
        }
 
+       if (found) {
+               vgaarb_info(&found->dev, "setting as boot device (VGA legacy resources not available)\n");
+               vga_set_default_device(found);
+               return;
+       }
+
        if (!vga_default_device()) {
                vgadev = list_first_entry_or_null(&vga_list,
                                                  struct vga_device, list);