[PATCH v4 6/9] bus: mhi: Load DDR training data using per-device serial number

[Kishore Batta <kishore.batta@oss.qualcomm.com>]

Devices may provide device-specific DDR training data that can be reused
across boot to avoid retraining and reduce boot time. The Sahara driver
currently always falls back to the default DDR training image, even when
per-device training data is available.

Extend the firmware loading logic to first attempt loading a per-device
DDR training image using the device serial number. If the serial-specific
image is not present, fallback to the existing default image, preserving
current behavior.

This change enables DDR training data reuse when available while keeping
the existing training flow unchanged for devices without saved data.

Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
 drivers/bus/mhi/sahara/sahara.c | 47 ++++++++++++++++++++++++++++++++---------
 1 file changed, 37 insertions(+), 10 deletions(-)

diff --git a/drivers/bus/mhi/sahara/sahara.c b/drivers/bus/mhi/sahara/sahara.c
index 4ea14c57774f51a778289d7409372a6ab21fea60..0a0f578aaa47ab2c4ca0765666b392fb9936ddd5 100644
--- a/drivers/bus/mhi/sahara/sahara.c
+++ b/drivers/bus/mhi/sahara/sahara.c
@@ -61,6 +61,8 @@
 #define SAHARA_MEM_DEBUG64_LENGTH	0x18
 #define SAHARA_MEM_READ64_LENGTH	0x18
 
+#define SAHARA_DDR_TRAINING_IMG_ID	34
+
 struct sahara_packet {
 	__le32 cmd;
 	__le32 length;
@@ -365,16 +367,41 @@ static int sahara_find_image(struct sahara_context *context, u32 image_id)
 		return 0;
 	}
 
-	/*
-	 * This image might be optional. The device may continue without it.
-	 * Only the device knows. Suppress error messages that could suggest an
-	 * a problem when we were actually able to continue.
-	 */
-	ret = sahara_request_fw(context, context->image_table[image_id]);
-	if (ret) {
-		dev_dbg(&context->mhi_dev->dev, "request for image id %d / file %s failed %d\n",
-			image_id, context->image_table[image_id], ret);
-		return ret;
+	/* DDR training special case: Try per-serial number file first */
+	if (image_id == SAHARA_DDR_TRAINING_IMG_ID && context->fw_folder) {
+		u32 serial_num = context->mhi_dev->mhi_cntrl->serial_number;
+
+		fw_path = kasprintf(GFP_KERNEL,
+				    "qcom/%s/mdmddr_0x%x.mbn",
+				    context->fw_folder, serial_num);
+		if (!fw_path)
+			return -ENOMEM;
+
+		ret = sahara_request_fw(context, fw_path);
+		kfree(fw_path);
+
+		if (ret) {
+			ret = sahara_request_fw(context, context->image_table[image_id]);
+			if (ret) {
+				dev_dbg(&context->mhi_dev->dev,
+					"request for image id %d / file %s failed %d\n",
+					image_id, context->image_table[image_id], ret);
+			}
+			return ret;
+		}
+	} else {
+		/*
+		 * This image might be optional. The device may continue without it.
+		 * Only the device knows. Suppress error messages that could suggest an
+		 * a problem when we were actually able to continue.
+		 */
+		ret = sahara_request_fw(context, context->image_table[image_id]);
+		if (ret) {
+			dev_dbg(&context->mhi_dev->dev,
+				"request for image id %d / file %s failed %d\n",
+				image_id, context->image_table[image_id], ret);
+			return ret;
+		}
 	}
 
 	context->active_image_id = image_id;

-- 
2.34.1