Re: [PATCH v4 7/9] bus: mhi: Capture DDR training data using command mode

On 3/19/2026 12:31 AM, Kishore Batta wrote:
> During early boot, devices may perform DDR training and produce training
> data that can be reused on subsequent boots to reduce initialization
> time. The sahara protocol provides a command mode flow to transfer this

Sahara

> training data to the host, but the driver currently does not handle
> command mode and drops the training payload.
> 
> Add Sahara command mode support to retrieve DDR training data from the
> device. When the device enters command mode and sends CMD_READY, query
> the support command list and request DDR training data using EXECUTE and
> EXECUTE_DATA. Allocate receive buffers based on the reported response
> size and copy the raw payload directly from the MHI DL completion
> callback.
> 
> Store the captured training data in controller-scoped memory using devres,
> so it remains available after sahara channel teardown. Also distinguish

Sahara

> raw payload completion from control packets in the DL callback, avoiding
> misinterpretation of training data as protocol messages, and requeue
> the RX buffer after switching back to IMAGE_TX_PENDING to allow the
> boot flow to continue.
> 
> Signed-off-by: Kishore Batta <[email protected]>
> ---
>   drivers/bus/mhi/sahara/sahara.c | 328 +++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 320 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/bus/mhi/sahara/sahara.c b/drivers/bus/mhi/sahara/sahara.c
> index 0a0f578aaa47ab2c4ca0765666b392fb9936ddd5..c88f1220199ac4373d3552167870c19a0d5f23b9 100644
> --- a/drivers/bus/mhi/sahara/sahara.c
> +++ b/drivers/bus/mhi/sahara/sahara.c
> @@ -5,11 +5,14 @@
>    */
>   
>   #include <linux/devcoredump.h>
> +#include <linux/device.h>
> +#include <linux/device/devres.h>
>   #include <linux/firmware.h>
>   #include <linux/limits.h>
>   #include <linux/mhi.h>
>   #include <linux/minmax.h>
>   #include <linux/mod_devicetable.h>
> +#include <linux/mutex.h>
>   #include <linux/overflow.h>
>   #include <linux/sahara.h>
>   #include <linux/types.h>
> @@ -60,8 +63,16 @@
>   #define SAHARA_RESET_LENGTH		0x8
>   #define SAHARA_MEM_DEBUG64_LENGTH	0x18
>   #define SAHARA_MEM_READ64_LENGTH	0x18
> -
> +#define SAHARA_COMMAND_READY_LENGTH	0x8
> +#define SAHARA_COMMAND_EXEC_RESP_LENGTH	0x10
> +#define SAHARA_COMMAND_EXECUTE_LENGTH	0xc
> +#define SAHARA_COMMAND_EXEC_DATA_LENGTH	0xc
> +#define SAHARA_SWITCH_MODE_LENGTH	0xc
> +
> +#define SAHARA_EXEC_CMD_GET_COMMAND_ID_LIST	0x8
> +#define SAHARA_EXEC_CMD_GET_TRAINING_DATA	0x9
>   #define SAHARA_DDR_TRAINING_IMG_ID	34

Why is the indentation of this line messed up?

> +#define SAHARA_NUM_CMD_BUF		SAHARA_NUM_TX_BUF
>   
>   struct sahara_packet {
>   	__le32 cmd;
> @@ -97,6 +108,19 @@ struct sahara_packet {
>   			__le64 memory_address;
>   			__le64 memory_length;
>   		} memory_read64;
> +		struct {
> +			__le32 client_command;
> +		} command_execute;
> +		struct {
> +			__le32 client_command;
> +			__le32 response_length;
> +		} command_execute_resp;
> +		struct {
> +			__le32 client_command;
> +		} command_exec_data;
> +		struct {
> +			__le32 mode;
> +		} mode_switch;
>   	};
>   };
>   
> @@ -163,6 +187,7 @@ struct sahara_context {
>   	struct work_struct		fw_work;
>   	struct work_struct		dump_work;
>   	struct work_struct		read_data_work;
> +	struct work_struct		cmd_work;
>   	struct mhi_device		*mhi_dev;
>   	const char * const		*image_table;
>   	u32				table_size;
> @@ -183,6 +208,24 @@ struct sahara_context {
>   	bool				is_mem_dump_mode;
>   	bool				non_streaming;
>   	const char			*fw_folder;
> +	bool				is_cmd_mode;
> +	bool				receiving_trng_data;

You already spell out "receiving", spell out "training".  I don't recall 
seeing "trng" before so it seems like a really uncommon shortform.

> +	size_t				trng_size;
> +	size_t				trng_rcvd;
> +	u32				trng_nbuf;
> +	char				*cmd_buff[SAHARA_NUM_CMD_BUF];
> +};