Re: [PATCH v6 5/7] bus: mhi: Load DDR training data using device serial number

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

On 7/9/2026 11:51 AM, Manivannan Sadhasivam wrote:
> On Wed, Jul 01, 2026 at 04:07:39PM +0530, Kishore Batta wrote:
>> 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 | 25 ++++++++++++++++++++++++-
>>   1 file changed, 24 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/bus/mhi/host/clients/sahara/sahara.c b/drivers/bus/mhi/host/clients/sahara/sahara.c
>> index 9adbd84859073d8024ba2a5fcfa33897439d6759..b5ca6353540dc3815db6539e7424afdb749fd3f6 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
>> @@ -235,7 +257,8 @@ static int sahara_find_image(struct sahara_context *context, u32 image_id)
>>   				      context->image_table[image_id],
>>   				      &context->mhi_dev->dev);
>>   	if (ret) {
>> -		dev_dbg(&context->mhi_dev->dev, "request for image id %d / file %s failed %d\n",
>> +		dev_dbg(&context->mhi_dev->dev,
>> +			"request for image id %d / file %s failed %d\n",
> Spurious change.
>
> - Mani

ACK. Will remove it in next version.