X86: Improve GOP detection in the EFI boot stub

We currently use the PCI IO protocol as a proxy for a functional GOP. This
is less than ideal, since some platforms will put the GOP on output devices
rather than the GPU itself. Move to using the conout protocol. This is not
guaranteed per-spec, but is part of the consplitter implementation that
causes this problem in the first place and so should be reliable.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

arch/x86/boot/compressed/eboot.c

@@ -276,28 +276,31 @@ static efi_status_t setup_gop(struct screen_info *si, efi_guid_t *proto,
 	nr_gops = size / sizeof(void *);
 	for (i = 0; i < nr_gops; i++) {
 		struct efi_graphics_output_mode_info *info;
-		efi_guid_t pciio_proto = EFI_PCI_IO_PROTOCOL_GUID;
-		void *pciio;
+		efi_guid_t conout_proto = EFI_CONSOLE_OUT_DEVICE_GUID;
+		bool conout_found = false;
+		void *dummy;
 		void *h = gop_handle[i];
 
 		status = efi_call_phys3(sys_table->boottime->handle_protocol,
 					h, proto, &gop);
 		if (status != EFI_SUCCESS)
 			continue;
 
-		efi_call_phys3(sys_table->boottime->handle_protocol,
-			       h, &pciio_proto, &pciio);
+		status = efi_call_phys3(sys_table->boottime->handle_protocol,
+					h, &conout_proto, &dummy);
+
+		if (status == EFI_SUCCESS)
+			conout_found = true;
 
 		status = efi_call_phys4(gop->query_mode, gop,
 					gop->mode->mode, &size, &info);
-		if (status == EFI_SUCCESS && (!first_gop || pciio)) {
+		if (status == EFI_SUCCESS && (!first_gop || conout_found)) {
 			/*
-			 * Apple provide GOPs that are not backed by
-			 * real hardware (they're used to handle
-			 * multiple displays). The workaround is to
-			 * search for a GOP implementing the PCIIO
-			 * protocol, and if one isn't found, to just
-			 * fallback to the first GOP.
+			 * Systems that use the UEFI Console Splitter may
+			 * provide multiple GOP devices, not all of which are
+			 * backed by real hardware. The workaround is to search
+			 * for a GOP implementing the ConOut protocol, and if
+			 * one isn't found, to just fall back to the first GOP.
 			 */
 			width = info->horizontal_resolution;
 			height = info->vertical_resolution;
@@ -308,10 +311,10 @@ static efi_status_t setup_gop(struct screen_info *si, efi_guid_t *proto,
 			pixels_per_scan_line = info->pixels_per_scan_line;
 
 			/*
-			 * Once we've found a GOP supporting PCIIO,
+			 * Once we've found a GOP supporting ConOut,
 			 * don't bother looking any further.
 			 */
-			if (pciio)
+			if (conout_found)
 				break;
 
 			first_gop = gop;

arch/x86/boot/compressed/eboot.h

@@ -14,6 +14,10 @@
 #define EFI_PAGE_SIZE		(1UL << EFI_PAGE_SHIFT)
 #define EFI_READ_CHUNK_SIZE	(1024 * 1024)
 
+#define EFI_CONSOLE_OUT_DEVICE_GUID    \
+	EFI_GUID(0xd3b36f2c, 0xd551, 0x11d4, 0x9a, 0x46, 0x0, 0x90, 0x27, \
+		  0x3f, 0xc1, 0x4d)
+
 #define PIXEL_RGB_RESERVED_8BIT_PER_COLOR		0
 #define PIXEL_BGR_RESERVED_8BIT_PER_COLOR		1
 #define PIXEL_BIT_MASK					2