[PATCH v8 5/7] bus: mhi: Load DDR training data using 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
serial specific training data is available.

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

This allows reuse of previously generated DDR training data when available,
while keeping the existing training flow unchanged for devices without
saved data or for all other firmware images.

Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com>
---
 drivers/bus/mhi/host/clients/sahara/sahara.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/bus/mhi/host/clients/sahara/sahara.c b/drivers/bus/mhi/host/clients/sahara/sahara.c
index 4baa47d0b94e326b5bfcaa80c8ddf008881c85c9..afb72910fd67b225cd77c44d7e835cae138c2ffb 100644
--- a/drivers/bus/mhi/host/clients/sahara/sahara.c
+++ b/drivers/bus/mhi/host/clients/sahara/sahara.c
@@ -59,6 +59,7 @@
 #define SAHARA_RESET_LENGTH		0x8
 #define SAHARA_MEM_DEBUG64_LENGTH	0x18
 #define SAHARA_MEM_READ64_LENGTH	0x18
+#define SAHARA_DDR_TRAINING_IMG_ID	34
 
 struct sahara_packet {
 	__le32 cmd;
@@ -226,6 +227,27 @@ static int sahara_find_image(struct sahara_context *context, u32 image_id)
 		return 0;
 	}
 
+	/* 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 = firmware_request_nowarn(&context->firmware,
+					      fw_path,
+					      &context->mhi_dev->dev);
+		kfree(fw_path);
+
+		if (!ret) {
+			context->active_image_id = 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

-- 
2.34.1