doc: Update the AXI-based recovery procedure

Signed-off-by: Tomasz Michalak <[email protected]>

Author: tmichalak

doc/source/axi_recovery_flow.md

@@ -14,25 +14,34 @@ The transactions to the core may be filtered using the AXI ID field (see {doc}`a
 
 The logic is implemented so that the recovery firmware in the Caliptra RoT ROM can operate without any changes.
 
+In order to enable setting W1C fields in recovery registers over AXI, the AXI recovery mode introduces additional register - `REC_INTF_REG_W1C_ACCESS`.
+
 ### AXI-based recovery procedure
 
 The Caliptra MCU RISC-V core is responsible for driving the data copied from an external memory (e.g. QSPI interface) to the recovery FIFOs.
 The ROM running on the MCU core monitors the recovery block registers and performs the recovery flow.
 During the boot procedure the ROM will have to follow the following procedure:
 
 1. Set the I3C block to the "direct AXI" mode
-2. Poll the `DEVICE_STATUS` register and wait for the recovery to be enabled by the Caliptra core
+   1. Set the `REC_INTF_BYPASS` bit in the `REC_INTF_CFG` register
+2. Poll the `DEVICE_STATUS_0` register and wait for the recovery to be enabled by the Caliptra core
+   1. Poll `DEVICE_STATUS_0.DEV_STATUS` until it becomes `0x03` (Recovery mode - ready to accept recovery image)
 3. Read the `RECOVERY_STATUS` register and check if the recovery flow started
-4. Write to the `RECOVERY_CONTROL` register to set the recovery image configuration
-5. Write to the `INDIRECT_FIFO_CTRL` register to set the recovery image size
-6. Push the recovery image to the recovery interface FIFOs:
-
-   a. Read the `INDIRECT_FIFO_STATUS` register to determine remaining space in the indirect FIFO
-   b. If the indirect FIFO is not full, write a chunk of data to the `INDIRECT_FIFO_DATA` register
-   c. The above steps should be repeated until the whole recovery image is written to the FIFO
-
-7. Activate the new image by writing to the `RECOVERY_CTRL` register
-8. Read the `RECOVERY_STATUS` register to ensure the image has been activated
+   1. Check whether `RECOVERY_STATUS.DEV_REC_STATUS` is `0x1` (Awaiting recovery image)
+4. Write to the `RECOVERY_CTRL` register to set the recovery image configuration
+5. Write to the `INDIRECT_FIFO_CTRL_0` register to reset the FIFO
+6. Write to the `INDIRECT_FIFO_CTRL_1` register to set the recovery image size
+7. Push the recovery image to the recovery interface FIFOs:
+   1. Read the `INDIRECT_FIFO_STATUS` register to determine remaining space in the indirect FIFO
+      1. If the indirect FIFO is not full, write a chunk of data to the `TX_DATA_PORT` register
+      2. If the indirect FIFO is full, wait for the `INDIRECT_FIFO_STATUS_0.FULL` bit to clear
+   2. The above steps should be repeated until the whole recovery image is written to the FIFO
+8. Notify the recovery handler that the final chunk has been sent
+   1. Set the `REC_PAYLOAD_DONE` bit in the `REC_INTF_CFG` register to raise the `payload_available` signal for the final time
+9. Activate the new image
+   1. Write `0xf00` to the `REC_INTF_REG_W1C_ACCESS` register to update the `RECOVERY_CTRL` field
+10. Read the `RECOVERY_STATUS` register to ensure the image has been activated
+    1. Poll `RECOVERY_STATUS.DEV_REC_STATUS` until it becomes `0x3` (Recovery successful); before the image is activated, this field will be `0x2` (Booting recovery image)
 
 The recovery image will be written in chunks with length equal to or less than `Max transfer size` defined in the `INDIRECT_FIFO_STATUS` register.
 Once the last data chunk is written to the FIFO, the Caliptra MCU ROM will write a CSR in the Secure Firmware Recovery register file indicating the transfer is complete.