remoteproc: qcom_q6v5_mss: Monitor MSS_STATUS for boot completion

On secure devices there exists a race condition which could lock the MSS
CONFIG AHB bus thus preventing access to BOOT_STATUS register during SSR.
Switch to polling the MSS_STATUS register with an additional 10 us delay
to reliably track boot completion.
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Link: https://lore.kernel.org/r/20200716120514.21588-1-sibis@codeaurora.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/qcom_q6v5_mss.c

@@ -112,8 +112,6 @@
 #define QDSP6SS_SLEEP                   0x3C
 #define QDSP6SS_BOOT_CORE_START         0x400
 #define QDSP6SS_BOOT_CMD                0x404
-#define QDSP6SS_BOOT_STATUS		0x408
-#define BOOT_STATUS_TIMEOUT_US		200
 #define BOOT_FSM_TIMEOUT                10000
 
 struct reg_info {
@@ -579,13 +577,15 @@ static int q6v5proc_reset(struct q6v5 *qproc)
 		/* De-assert the Q6 stop core signal */
 		writel(1, qproc->reg_base + QDSP6SS_BOOT_CORE_START);
 
+		/* Wait for 10 us for any staggering logic to settle */
+		usleep_range(10, 20);
+
 		/* Trigger the boot FSM to start the Q6 out-of-reset sequence */
 		writel(1, qproc->reg_base + QDSP6SS_BOOT_CMD);
 
-		/* Poll the QDSP6SS_BOOT_STATUS for FSM completion */
-		ret = readl_poll_timeout(qproc->reg_base + QDSP6SS_BOOT_STATUS,
-					 val, (val & BIT(0)) != 0, 1,
-					 BOOT_STATUS_TIMEOUT_US);
+		/* Poll the MSS_STATUS for FSM completion */
+		ret = readl_poll_timeout(qproc->rmb_base + RMB_MBA_MSS_STATUS,
+					 val, (val & BIT(0)) != 0, 10, BOOT_FSM_TIMEOUT);
 		if (ret) {
 			dev_err(qproc->dev, "Boot FSM failed to complete.\n");
 			/* Reset the modem so that boot FSM is in reset state */