[PATCH v3] bus: mhi: Fix race while handling SYS_ERR at power up

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

Some devices tend to trigger SYS_ERR interrupt while the host handling
SYS_ERR state of the device during power up. This creates a race
condition and causes a failure in booting up the device.

The issue is seen on the Sierra Wireless EM9191 modem during SYS_ERR
handling in mhi_async_power_up(). Once the host detects that the device
is in SYS_ERR state, it issues MHI_RESET and waits for the device to
process the reset request. During this time, the device triggers SYS_ERR
interrupt to the host and host starts handling SYS_ERR execution.

So by the time the device has completed reset, host starts SYS_ERR
handling. This causes the race condition and the modem fails to boot.

Hence, register the IRQ handler only after handling the SYS_ERR check
to avoid getting spurious IRQs from the device.

Cc: stable@vger.kernel.org
Fixes: e18d4e9fa79b ("bus: mhi: core: Handle syserr during power_up")
Reported-by: Aleksander Morgado <aleksander@aleksander.es>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---

Changes in v3:

* Moved BHI_INTVEC setup after irq setup
* Used interval_us as the delay for the polling API

Changes in v2:

* Switched to "mhi_poll_reg_field" for detecting MHI reset in device.

 drivers/bus/mhi/core/pm.c | 38 ++++++++++++++------------------------
 1 file changed, 14 insertions(+), 24 deletions(-)

diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
index fb99e3727155..ee0515a25e46 100644
--- a/drivers/bus/mhi/core/pm.c
+++ b/drivers/bus/mhi/core/pm.c
@@ -1038,7 +1038,7 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
 	enum mhi_ee_type current_ee;
 	enum dev_st_transition next_state;
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
-	u32 val;
+	u32 interval_us = 25000; /* poll register field every 25 milliseconds */
 	int ret;
 
 	dev_info(dev, "Requested to power ON\n");
@@ -1055,13 +1055,7 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
 	mutex_lock(&mhi_cntrl->pm_mutex);
 	mhi_cntrl->pm_state = MHI_PM_DISABLE;
 
-	ret = mhi_init_irq_setup(mhi_cntrl);
-	if (ret)
-		goto error_setup_irq;
-
-	/* Setup BHI INTVEC */
 	write_lock_irq(&mhi_cntrl->pm_lock);
-	mhi_write_reg(mhi_cntrl, mhi_cntrl->bhi, BHI_INTVEC, 0);
 	mhi_cntrl->pm_state = MHI_PM_POR;
 	mhi_cntrl->ee = MHI_EE_MAX;
 	current_ee = mhi_get_exec_env(mhi_cntrl);
@@ -1072,7 +1066,7 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
 		dev_err(dev, "%s is not a valid EE for power on\n",
 			TO_MHI_EXEC_STR(current_ee));
 		ret = -EIO;
-		goto error_async_power_up;
+		goto error_setup_irq;
 	}
 
 	state = mhi_get_mhi_state(mhi_cntrl);
@@ -1081,20 +1075,12 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
 
 	if (state == MHI_STATE_SYS_ERR) {
 		mhi_set_mhi_state(mhi_cntrl, MHI_STATE_RESET);
-		ret = wait_event_timeout(mhi_cntrl->state_event,
-				MHI_PM_IN_FATAL_STATE(mhi_cntrl->pm_state) ||
-					mhi_read_reg_field(mhi_cntrl,
-							   mhi_cntrl->regs,
-							   MHICTRL,
-							   MHICTRL_RESET_MASK,
-							   MHICTRL_RESET_SHIFT,
-							   &val) ||
-					!val,
-				msecs_to_jiffies(mhi_cntrl->timeout_ms));
-		if (!ret) {
-			ret = -EIO;
+		ret = mhi_poll_reg_field(mhi_cntrl, mhi_cntrl->regs, MHICTRL,
+				 MHICTRL_RESET_MASK, MHICTRL_RESET_SHIFT, 0,
+				 interval_us);
+		if (ret) {
 			dev_info(dev, "Failed to reset MHI due to syserr state\n");
-			goto error_async_power_up;
+			goto error_setup_irq;
 		}
 
 		/*
@@ -1104,6 +1090,13 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
 		mhi_write_reg(mhi_cntrl, mhi_cntrl->bhi, BHI_INTVEC, 0);
 	}
 
+	ret = mhi_init_irq_setup(mhi_cntrl);
+	if (ret)
+		goto error_setup_irq;
+
+	/* Setup BHI INTVEC */
+	mhi_write_reg(mhi_cntrl, mhi_cntrl->bhi, BHI_INTVEC, 0);
+
 	/* Transition to next state */
 	next_state = MHI_IN_PBL(current_ee) ?
 		DEV_ST_TRANSITION_PBL : DEV_ST_TRANSITION_READY;
@@ -1116,9 +1109,6 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
 
 	return 0;
 
-error_async_power_up:
-	mhi_deinit_free_irq(mhi_cntrl);
-
 error_setup_irq:
 	mhi_cntrl->pm_state = MHI_PM_DISABLE;
 	mutex_unlock(&mhi_cntrl->pm_mutex);
-- 
2.25.1