amdgpu: detect if we are using atomfirmware or atombios for vbios (v2)

Supposedly atomfirmware rom header is 3.3 atombios is 1.1.

v2: rebased on newer kernel
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

@@ -1308,6 +1308,7 @@ struct amdgpu_device {
 	bool				have_disp_power_ref;
 
 	/* BIOS */
+	bool				is_atom_fw;
 	uint8_t				*bios;
 	uint32_t			bios_size;
 	struct amdgpu_bo		*stollen_vga_memory;

drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c

@@ -86,6 +86,18 @@ static bool check_atom_bios(uint8_t *bios, size_t size)
 	return false;
 }
 
+static bool is_atom_fw(uint8_t *bios)
+{
+	uint16_t bios_header_start = bios[0x48] | (bios[0x49] << 8);
+	uint8_t frev = bios[bios_header_start + 2];
+	uint8_t crev = bios[bios_header_start + 3];
+
+	if ((frev < 3) ||
+	    ((frev == 3) && (crev < 3)))
+		return false;
+
+	return true;
+}
 
 /* If you boot an IGP board with a discrete card as the primary,
  * the IGP rom is not accessible via the rom bar as the IGP rom is
@@ -419,26 +431,30 @@ static inline bool amdgpu_acpi_vfct_bios(struct amdgpu_device *adev)
 bool amdgpu_get_bios(struct amdgpu_device *adev)
 {
 	if (amdgpu_atrm_get_bios(adev))
-		return true;
+		goto success;
 
 	if (amdgpu_acpi_vfct_bios(adev))
-		return true;
+		goto success;
 
 	if (igp_read_bios_from_vram(adev))
-		return true;
+		goto success;
 
 	if (amdgpu_read_bios(adev))
-		return true;
+		goto success;
 
 	if (amdgpu_read_bios_from_rom(adev))
-		return true;
+		goto success;
 
 	if (amdgpu_read_disabled_bios(adev))
-		return true;
+		goto success;
 
 	if (amdgpu_read_platform_bios(adev))
-		return true;
+		goto success;
 
 	DRM_ERROR("Unable to locate a BIOS ROM\n");
 	return false;
+
+success:
+	adev->is_atom_fw = is_atom_fw(adev->bios);
+	return true;
 }