[PATCH v2] mhi: pci_generic: Ensure device readiness before starting MHI

[PATCH v2] mhi: pci_generic: Ensure device readiness before starting MHI

[Loic Poulain]

The PCI device may have not been bound from cold boot and be in
undefined state, or simply not yet ready for MHI operations. This
change ensures that the MHI layer is reset to initial state and
ready for MHI initialization and power up.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
---
 v2: reset only if necessary

 drivers/bus/mhi/pci_generic.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/bus/mhi/pci_generic.c b/drivers/bus/mhi/pci_generic.c
index c20f59e..ea68c9d 100644
--- a/drivers/bus/mhi/pci_generic.c
+++ b/drivers/bus/mhi/pci_generic.c
@@ -17,6 +17,8 @@
 #include <linux/timer.h>
 #include <linux/workqueue.h>
 
+#include "core/internal.h"
+
 #define MHI_PCI_DEFAULT_BAR_NUM 0
 
 #define MHI_POST_RESET_DELAY_MS 500
@@ -391,6 +393,27 @@ static void health_check(struct timer_list *t)
 	mod_timer(&mhi_pdev->health_check_timer, jiffies + HEALTH_CHECK_PERIOD);
 }
 
+static void __mhi_sw_reset(struct mhi_controller *mhi_cntrl)
+{
+	unsigned int max_wait_ready = 100;
+
+	if (mhi_get_mhi_state(mhi_cntrl) >= MHI_STATE_M0) {
+		dev_warn(mhi_cntrl->cntrl_dev, "Need reset\n");
+		/* try to reset */
+		writel(MHICTRL_RESET_MASK, mhi_cntrl->regs + MHICTRL);
+		msleep(10);
+	}
+
+	while (mhi_get_mhi_state(mhi_cntrl) != MHI_STATE_READY) {
+		if (!max_wait_ready--) {
+			dev_warn(mhi_cntrl->cntrl_dev, "Not ready (state %u)\n",
+				 mhi_get_mhi_state(mhi_cntrl));
+			break;
+		}
+		msleep(50);
+	}
+}
+
 static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 {
 	const struct mhi_pci_dev_info *info = (struct mhi_pci_dev_info *) id->driver_data;
@@ -451,6 +474,9 @@ static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 		goto err_unregister;
 	}
 
+	/* Before starting MHI, ensure device is in good initial state */
+	__mhi_sw_reset(mhi_cntrl);
+
 	err = mhi_sync_power_up(mhi_cntrl);
 	if (err) {
 		dev_err(&pdev->dev, "failed to power up MHI controller\n");
@@ -532,6 +558,8 @@ static void mhi_pci_reset_done(struct pci_dev *pdev)
 		return;
 	}
 
+	__mhi_sw_reset(mhi_cntrl);
+
 	err = mhi_sync_power_up(mhi_cntrl);
 	if (err) {
 		dev_err(&pdev->dev, "failed to power up MHI controller\n");
-- 
2.7.4