Re: [PATCH v4 1/3] bus: mhi: host: add mhi_power_down_keep_dev()

Baochen Qiang <quic_bqiang@xxxxxxxxxxx> · Thu, 29 Feb 2024 18:33:43 +0800

On 2/29/2024 6:12 PM, Manivannan Sadhasivam wrote:
On Wed, Feb 28, 2024 at 10:22:41AM +0800, Baochen Qiang wrote:
ath11k fails to resume:

ath11k_pci 0000:06:00.0: timeout while waiting for restart complete

This happens because when calling mhi_sync_power_up() the MHI subsystem
eventually calls device_add() from mhi_create_devices() but the device
creation is deferred:

mhi mhi0_IPCR: Driver qcom_mhi_qrtr force probe deferral

The reason for deferring device creation is explained in dpm_prepare():

         /*
          * It is unsafe if probing of devices will happen during suspend or
          * hibernation and system behavior will be unpredictable in this case.
          * So, let's prohibit device's probing here and defer their probes
          * instead. The normal behavior will be restored in dpm_complete().
          */

Because the device probe is deferred, the qcom_mhi_qrtr_probe() is not
called and thus MHI channels are not prepared:

So what this means that QRTR is not delivering messages and the QMI connection
is not working between ath11k and the firmware, resulting a failure in firmware
initialization.

To fix this add new function mhi_power_down_keep_dev() which doesn't destroy
the devices for channels during power down. This way we avoid probe defer issue
and finally can get ath11k hibernation working with the following patches.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.30

Signed-off-by: Kalle Valo <quic_kvalo@xxxxxxxxxxx>

Did Kalle co-author this patch? If so, his Co-developed-by tag should be
added.
Hmm, I'm not sure...  I would like Kalle's thoughts on this.


Signed-off-by: Baochen Qiang <quic_bqiang@xxxxxxxxxxx>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>

- Mani

---
  drivers/bus/mhi/host/internal.h |  4 +++-
  drivers/bus/mhi/host/pm.c       | 42 ++++++++++++++++++++++++++++-----
  include/linux/mhi.h             | 18 +++++++++++++-
  3 files changed, 56 insertions(+), 8 deletions(-)

diff --git a/drivers/bus/mhi/host/internal.h b/drivers/bus/mhi/host/internal.h
index 5fe49311b8eb..aaad40a07f69 100644
--- a/drivers/bus/mhi/host/internal.h
+++ b/drivers/bus/mhi/host/internal.h
@@ -80,6 +80,7 @@ enum dev_st_transition {
  	DEV_ST_TRANSITION_FP,
  	DEV_ST_TRANSITION_SYS_ERR,
  	DEV_ST_TRANSITION_DISABLE,
+	DEV_ST_TRANSITION_DISABLE_DESTROY_DEVICE,
  	DEV_ST_TRANSITION_MAX,
  };
  
@@ -90,7 +91,8 @@ enum dev_st_transition {
  	dev_st_trans(MISSION_MODE,	"MISSION MODE")		\
  	dev_st_trans(FP,		"FLASH PROGRAMMER")	\
  	dev_st_trans(SYS_ERR,		"SYS ERROR")		\
-	dev_st_trans_end(DISABLE,	"DISABLE")
+	dev_st_trans(DISABLE,		"DISABLE")		\
+	dev_st_trans_end(DISABLE_DESTROY_DEVICE, "DISABLE (DESTROY DEVICE)")
  
  extern const char * const dev_state_tran_str[DEV_ST_TRANSITION_MAX];
  #define TO_DEV_STATE_TRANS_STR(state) (((state) >= DEV_ST_TRANSITION_MAX) ? \
diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
index 8b40d3f01acc..11c0e751f223 100644
--- a/drivers/bus/mhi/host/pm.c
+++ b/drivers/bus/mhi/host/pm.c
@@ -468,7 +468,8 @@ static int mhi_pm_mission_mode_transition(struct mhi_controller *mhi_cntrl)
  }
  
  /* Handle shutdown transitions */
-static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
+static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl,
+				      bool destroy_device)
  {
  	enum mhi_pm_state cur_state;
  	struct mhi_event *mhi_event;
@@ -530,8 +531,16 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
  	dev_dbg(dev, "Waiting for all pending threads to complete\n");
  	wake_up_all(&mhi_cntrl->state_event);
  
-	dev_dbg(dev, "Reset all active channels and remove MHI devices\n");
-	device_for_each_child(&mhi_cntrl->mhi_dev->dev, NULL, mhi_destroy_device);
+	/*
+	 * Only destroy the 'struct device' for channels if indicated by the
+	 * 'destroy_device' flag. Because, during system suspend or hibernation
+	 * state, there is no need to destroy the 'struct device' as the endpoint
+	 * device would still be physically attached to the machine.
+	 */
+	if (destroy_device) {
+		dev_dbg(dev, "Reset all active channels and remove MHI devices\n");
+		device_for_each_child(&mhi_cntrl->mhi_dev->dev, NULL, mhi_destroy_device);
+	}
  
  	mutex_lock(&mhi_cntrl->pm_mutex);
  
@@ -821,7 +830,10 @@ void mhi_pm_st_worker(struct work_struct *work)
  			mhi_pm_sys_error_transition(mhi_cntrl);
  			break;
  		case DEV_ST_TRANSITION_DISABLE:
-			mhi_pm_disable_transition(mhi_cntrl);
+			mhi_pm_disable_transition(mhi_cntrl, false);
+			break;
+		case DEV_ST_TRANSITION_DISABLE_DESTROY_DEVICE:
+			mhi_pm_disable_transition(mhi_cntrl, true);
  			break;
  		default:
  			break;
@@ -1175,7 +1187,8 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
  }
  EXPORT_SYMBOL_GPL(mhi_async_power_up);
  
-void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
+static void __mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful,
+			     bool destroy_device)
  {
  	enum mhi_pm_state cur_state, transition_state;
  	struct device *dev = &mhi_cntrl->mhi_dev->dev;
@@ -1211,15 +1224,32 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
  	write_unlock_irq(&mhi_cntrl->pm_lock);
  	mutex_unlock(&mhi_cntrl->pm_mutex);
  
-	mhi_queue_state_transition(mhi_cntrl, DEV_ST_TRANSITION_DISABLE);
+	if (destroy_device)
+		mhi_queue_state_transition(mhi_cntrl,
+					   DEV_ST_TRANSITION_DISABLE_DESTROY_DEVICE);
+	else
+		mhi_queue_state_transition(mhi_cntrl,
+					   DEV_ST_TRANSITION_DISABLE);
  
  	/* Wait for shutdown to complete */
  	flush_work(&mhi_cntrl->st_worker);
  
  	disable_irq(mhi_cntrl->irq[0]);
  }
+
+void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
+{
+	__mhi_power_down(mhi_cntrl, graceful, true);
+}
  EXPORT_SYMBOL_GPL(mhi_power_down);
  
+void mhi_power_down_keep_dev(struct mhi_controller *mhi_cntrl,
+			       bool graceful)
+{
+	__mhi_power_down(mhi_cntrl, graceful, false);
+}
+EXPORT_SYMBOL_GPL(mhi_power_down_keep_dev);
+
  int mhi_sync_power_up(struct mhi_controller *mhi_cntrl)
  {
  	int ret = mhi_async_power_up(mhi_cntrl);
diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index 77b8c0a26674..cde01e133a1b 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -630,12 +630,28 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl);
  int mhi_sync_power_up(struct mhi_controller *mhi_cntrl);
  
  /**
- * mhi_power_down - Start MHI power down sequence
+ * mhi_power_down - Power down the MHI device and also destroy the
+ *                  'struct device' for the channels associated with it.
+ *                  See also mhi_power_down_keep_dev() which is a variant
+ *                  of this API that keeps the 'struct device' for channels
+ *                  (useful during suspend/hibernation).
   * @mhi_cntrl: MHI controller
   * @graceful: Link is still accessible, so do a graceful shutdown process
   */
  void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful);
  
+/**
+ * mhi_power_down_keep_dev - Power down the MHI device but keep the 'struct
+ *                           device' for the channels associated with it.
+ *                           This is a variant of 'mhi_power_down()' and
+ *                           useful in scenarios such as suspend/hibernation
+ *                           where destroying of the 'struct device' is not
+ *                           needed.
+ * @mhi_cntrl: MHI controller
+ * @graceful: Link is still accessible, so do a graceful shutdown process
+ */
+void mhi_power_down_keep_dev(struct mhi_controller *mhi_cntrl, bool graceful);
+
  /**
   * mhi_unprepare_after_power_down - Free any allocated memory after power down
   * @mhi_cntrl: MHI controller
--
2.25.1









