drm/msm: support firmware-name for zap fw (v2)

Since zap firmware can be device specific, allow for a firmware-name
property in the zap node to specify which firmware to load, similarly to
the scheme used for dsp/wifi/etc.

v2: only need a single error msg when we can't load from firmware-name
    specified path, and fix comment [Bjorn A.]
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Jordan Crouse <jcrouse@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/gpu/drm/msm/adreno/adreno_gpu.c

@@ -26,6 +26,7 @@ static int zap_shader_load_mdt(struct msm_gpu *gpu, const char *fwname,
 {
 	struct device *dev = &gpu->pdev->dev;
 	const struct firmware *fw;
+	const char *signed_fwname = NULL;
 	struct device_node *np, *mem_np;
 	struct resource r;
 	phys_addr_t mem_phys;
@@ -58,8 +59,31 @@ static int zap_shader_load_mdt(struct msm_gpu *gpu, const char *fwname,
 
 	mem_phys = r.start;
 
-	/* Request the MDT file for the firmware */
-	fw = adreno_request_fw(to_adreno_gpu(gpu), fwname);
+	/*
+	 * Check for a firmware-name property.  This is the new scheme
+	 * to handle firmware that may be signed with device specific
+	 * keys, allowing us to have a different zap fw path for different
+	 * devices.
+	 *
+	 * If the firmware-name property is found, we bypass the
+	 * adreno_request_fw() mechanism, because we don't need to handle
+	 * the /lib/firmware/qcom/* vs /lib/firmware/* case.
+	 *
+	 * If the firmware-name property is not found, for backwards
+	 * compatibility we fall back to the fwname from the gpulist
+	 * table.
+	 */
+	of_property_read_string_index(np, "firmware-name", 0, &signed_fwname);
+	if (signed_fwname) {
+		fwname = signed_fwname;
+		ret = request_firmware_direct(&fw, fwname, gpu->dev->dev);
+		if (ret)
+			fw = ERR_PTR(ret);
+	} else {
+		/* Request the MDT file from the default location: */
+		fw = adreno_request_fw(to_adreno_gpu(gpu), fwname);
+	}
+
 	if (IS_ERR(fw)) {
 		DRM_DEV_ERROR(dev, "Unable to load %s\n", fwname);
 		return PTR_ERR(fw);
@@ -95,7 +119,7 @@ static int zap_shader_load_mdt(struct msm_gpu *gpu, const char *fwname,
 	 * not.  But since we've already gotten through adreno_request_fw()
 	 * we know which of the two cases it is:
 	 */
-	if (to_adreno_gpu(gpu)->fwloc == FW_LOCATION_LEGACY) {
+	if (signed_fwname || (to_adreno_gpu(gpu)->fwloc == FW_LOCATION_LEGACY)) {
 		ret = qcom_mdt_load(dev, fw, fwname, pasid,
 				mem_region, mem_phys, mem_size, NULL);
 	} else {