bus: mhi: core: Add support for Flash Programmer execution environment

MHI WWAN modems support downloading firmware to NAND or eMMC
using Firehose protocol with process as follows:
1. Modem boots up, enters AMSS execution environment and the
device later enters EDL (Emergency Download) mode through any
mechanism host can use such as a diag command.
2. Modem enters SYS_ERROR, MHI host handles SYS_ERROR transition.
3. EDL image for device to enter 'Flash Programmer' execution
environment is then flashed via BHI interface from host.
4. Modem enters MHI READY -> M0 and sends the Flash Programmer
execution environment change to host.
5. Following that, EDL/FIREHOSE channels (34, 35) are made
available from the host.
6. User space tool for downloading firmware image to modem over
the EDL channels using Firehose protocol. Link to USB flashing
tool: https://git.linaro.org/landing-teams/working/qualcomm/qdl.git/

Make the necessary changes to allow for this sequence to occur and
allow using the Flash Programmer execution environment.
Signed-off-by: NCarl Yin <carl.yin@quectel.com>
Co-developed-by: NBhaumik Bhatt <bbhatt@codeaurora.org>
Signed-off-by: NBhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: NLoic Poulain <loic.poulain@linaro.org>
Reviewed-by: NManivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/1617067704-28850-5-git-send-email-bbhatt@codeaurora.orgSigned-off-by: NManivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

drivers/bus/mhi/core/init.c

@@ -29,6 +29,7 @@ const char * const mhi_ee_str[MHI_EE_MAX] = {
 	[MHI_EE_WFW] = "WFW",
 	[MHI_EE_PTHRU] = "PASS THRU",
 	[MHI_EE_EDL] = "EDL",
+	[MHI_EE_FP] = "FLASH PROGRAMMER",
 	[MHI_EE_DISABLE_TRANSITION] = "DISABLE",
 	[MHI_EE_NOT_SUPPORTED] = "NOT SUPPORTED",
 };
@@ -38,6 +39,7 @@ const char * const dev_state_tran_str[DEV_ST_TRANSITION_MAX] = {
 	[DEV_ST_TRANSITION_READY] = "READY",
 	[DEV_ST_TRANSITION_SBL] = "SBL",
 	[DEV_ST_TRANSITION_MISSION_MODE] = "MISSION_MODE",
+	[DEV_ST_TRANSITION_FP] = "FLASH_PROGRAMMER",
 	[DEV_ST_TRANSITION_SYS_ERR] = "SYS_ERR",
 	[DEV_ST_TRANSITION_DISABLE] = "DISABLE",
 };

drivers/bus/mhi/core/internal.h

@@ -386,6 +386,7 @@ enum dev_st_transition {
 	DEV_ST_TRANSITION_READY,
 	DEV_ST_TRANSITION_SBL,
 	DEV_ST_TRANSITION_MISSION_MODE,
+	DEV_ST_TRANSITION_FP,
 	DEV_ST_TRANSITION_SYS_ERR,
 	DEV_ST_TRANSITION_DISABLE,
 	DEV_ST_TRANSITION_MAX,

drivers/bus/mhi/core/main.c

@@ -831,6 +831,9 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
 			case MHI_EE_AMSS:
 				st = DEV_ST_TRANSITION_MISSION_MODE;
 				break;
+			case MHI_EE_FP:
+				st = DEV_ST_TRANSITION_FP;
+				break;
 			case MHI_EE_RDDM:
 				mhi_cntrl->status_cb(mhi_cntrl, MHI_CB_EE_RDDM);
 				write_lock_irq(&mhi_cntrl->pm_lock);

drivers/bus/mhi/core/pm.c

@@ -782,6 +782,12 @@ void mhi_pm_st_worker(struct work_struct *work)
 		case DEV_ST_TRANSITION_MISSION_MODE:
 			mhi_pm_mission_mode_transition(mhi_cntrl);
 			break;
+		case DEV_ST_TRANSITION_FP:
+			write_lock_irq(&mhi_cntrl->pm_lock);
+			mhi_cntrl->ee = MHI_EE_FP;
+			write_unlock_irq(&mhi_cntrl->pm_lock);
+			mhi_create_devices(mhi_cntrl);
+			break;
 		case DEV_ST_TRANSITION_READY:
 			mhi_ready_state_transition(mhi_cntrl);
 			break;

include/linux/mhi.h

@@ -117,6 +117,7 @@ struct mhi_link_info {
  * @MHI_EE_WFW: WLAN firmware mode
  * @MHI_EE_PTHRU: Passthrough
  * @MHI_EE_EDL: Embedded downloader
+ * @MHI_EE_FP: Flash Programmer Environment
  */
 enum mhi_ee_type {
 	MHI_EE_PBL,
@@ -126,7 +127,8 @@ enum mhi_ee_type {
 	MHI_EE_WFW,
 	MHI_EE_PTHRU,
 	MHI_EE_EDL,
-	MHI_EE_MAX_SUPPORTED = MHI_EE_EDL,
+	MHI_EE_FP,
+	MHI_EE_MAX_SUPPORTED = MHI_EE_FP,
 	MHI_EE_DISABLE_TRANSITION, /* local EE, not related to mhi spec */
 	MHI_EE_NOT_SUPPORTED,
 	MHI_EE_MAX,