On 7/8/2026 10:16 AM, Randy Dunlap wrote:
On 7/1/26 3:37 AM, Kishore Batta wrote:
+The packet flow sequence is as follows :
+
+1. The target sends the hello packet to the host to initiate the protocol
+ with the mode set to image transfer pending.
+
+2. The host sends a hello response packet with a success status and sets the
+ mode to image transfer pending after it receives the hello packet and
+ validates the protocol version running on the target.
+
+3. After the target receives the hello response, it initiates the data
+ transfer by requesting the size of DDR training/calibration data.
+
+4. The host sends back the DDR training/calibration data to the target.
+
+5. The target decodes the training data and does not find valid DDR
+ calibration data, target sends END_IMAGE_TX to interrupt the transfer.
+
+6. The host sends DONE after receives END_IMAGE_TX.
+
+7. The target sends DONE_RESP with mode = IMAGE_TX_PENDING because it has
+ not received all images.
+
+8. The target executes DDR training process to generate valid DDR calibration
+ data and prepares to push back to host.
+
+9. The target initiates protocol by sending a hello packet with COMMAND_MODE
+ to the host.
+
+10. The host sends a hello response packet with a success status and sets the
+ mode to COMMAND_MODE.
+
+11. The target sends CMD_READY to the host.
+
+12. The host receives CMD_READY and starts to get command IDs to be executed.
+
+13. The target sends CMD_ID = 9 to push DDR calibration data to host.
+
+14. The host executes CMD_ID = 9 to get DDR calibration data from the target.
+
+15. The target sends RAW_DATA with the payload which contains DDR calibration
+ data to host.
+
+16. The host saves training data in the kernel buffer and exposes to userspace
+ via the sysfs entry. The host sends CMD_SWITCH_MODE with the mode set to
+ IMAGE_TX_PENDING to continue booting.
+
+17. After the target receives the CMD_SWITCH_MODE command, it sends HELLO to
+ the host with the mode set to IMAGE_TX_PENDING. The target and the host
+ repeat the packet flow for image transfer to get all booting-required
+ images.
+
+18. Upon successful transfer of all images, the target sends an END_IMAGE_TX
+ packet with a success status to the host.
+
+19. The host sends DONE after it receives END_IMAGE_TX.
+
+20. The target sends DONE_RESP with the mode set to IMAGE_TX_COMPLETE because
+ it has received all images. The process has been completed after the host
+ receives DONE_RESP with the mode set to IMAGE_TX_COMPLETE.
+
+Subsequent boot scenario with valid DDR calibration data
+--------------------------------------------------------
+
+The below firgure shows the subsequent boot scenario with valid DDR calibration
+data process being loaded from host to target.
+
+.. code-block:: text
+
+ Host Target
+ | HELLO |
+ | (mode = image transfer) |
+ |<--------------------------|
+ | |
+ | HELLO RESP |
+ | (mode = image transfer) |
+ |-------------------------->|
+ | |
+ | READ_DATA |
+ | (img ID:34, 0, offset, |
+ | size of DDR training data)|
+ |<--------------------------|
+ | |
+ | RAW_DATA |
+ |(size of DDR training data)|
+ |-------------------------->|
+ | |
+ | |
+ | END_IMAGE_TX |
+ |<--------------------------|
+ | |
+ | |
+ | DONE |
+ |-------------------------->|
+ | |
+ | |
+ | DONE_RESP |
+ | (mode = IMAGE_TX_PENDING) |
+ |<--------------------------|
+ | |
+ | Subsequent boot scenario |
+ | (valid calibration data) |
+ | DDR driver configures DDR |
+ | using valid calibration |
+ | data |
+ | |
+ | |
+ | HELLO |
+ | (mode = IMAGE_TX_PENDING) |
+ |<--------------------------|
+ | |
+ | HELLO RESP |
+ | (mode = IMAGE_TX_PENDING) |
+ |-------------------------->|
+ | |
+ | Boot/Load rest of the |
+ | images.... |
+ | |
+ | END_IMAGE_TX |
+ |<--------------------------|
+ | |
+ | |
+ | DONE |
+ |-------------------------->|
+ | |
+ | |
+ | DONE_RESP |
+ |(mode = IMAGE_TX_COMPLETE) |
+ |<--------------------------|
+ | |
+
+The packet flow is as follows :
+
s/as follows :/as follows:/
in 2 places.
ACK. I'll remove the extra space before the colon in both places in the
next version.
+1. The target sends the hello packet to the host to initiate the protocol
+ with the mode set to image transfer pending.
