bus: mhi: core: Add support for forced PM resume

For whatever reason, some devices like QCA6390, WCN6855 using ath11k
are not in M3 state during PM resume, but still functional. The
mhi_pm_resume should then not fail in those cases, and let the higher
level device specific stack continue resuming process.

Add an API mhi_pm_resume_force(), to force resuming irrespective of the
current MHI state. This fixes a regression with non functional ath11k WiFi
after suspend/resume cycle on some machines.

Bug report: https://bugzilla.kernel.org/show_bug.cgi?id=214179

Link: https://lore.kernel.org/regressions/[e-mail]/
Fixes: 020d3b26c07a ("bus: mhi: Early MHI resume failure in non M3 state")
Cc: [e-mail] #5.13
Reported-by: Kalle Valo <[e-mail]>
Reported-by: Pengyu Ma <[e-mail]>
Tested-by: Kalle Valo <[e-mail]>
Acked-by: Kalle Valo <[e-mail]>
Signed-off-by: Loic Poulain <[e-mail]>
[mani: Switched to API, added bug report, reported-by tags and CCed stable]
Signed-off-by: Manivannan Sadhasivam <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/bus/mhi/core/pm.c

···
 }
 EXPORT_SYMBOL_GPL(mhi_pm_suspend);
 
-int mhi_pm_resume(struct mhi_controller *mhi_cntrl)
+static int __mhi_pm_resume(struct mhi_controller *mhi_cntrl, bool force)
 {
 	struct mhi_chan *itr, *tmp;
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
···
 	if (MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state))
 		return -EIO;
 
-	if (mhi_get_mhi_state(mhi_cntrl) != MHI_STATE_M3)
-		return -EINVAL;
+	if (mhi_get_mhi_state(mhi_cntrl) != MHI_STATE_M3) {
+		dev_warn(dev, "Resuming from non M3 state (%s)\n",
+			 TO_MHI_STATE_STR(mhi_get_mhi_state(mhi_cntrl)));
+		if (!force)
+			return -EINVAL;
+	}
 
 	/* Notify clients about exiting LPM */
 	list_for_each_entry_safe(itr, tmp, &mhi_cntrl->lpm_chans, node) {
···
 
 	return 0;
 }
+
+int mhi_pm_resume(struct mhi_controller *mhi_cntrl)
+{
+	return __mhi_pm_resume(mhi_cntrl, false);
+}
 EXPORT_SYMBOL_GPL(mhi_pm_resume);
+
+int mhi_pm_resume_force(struct mhi_controller *mhi_cntrl)
+{
+	return __mhi_pm_resume(mhi_cntrl, true);
+}
+EXPORT_SYMBOL_GPL(mhi_pm_resume_force);
 
 int __mhi_device_get_sync(struct mhi_controller *mhi_cntrl)
 {

drivers/net/wireless/ath/ath11k/mhi.c

···
 		ret = mhi_pm_suspend(ab_pci->mhi_ctrl);
 		break;
 	case ATH11K_MHI_RESUME:
-		ret = mhi_pm_resume(ab_pci->mhi_ctrl);
+		/* Do force MHI resume as some devices like QCA6390, WCN6855
+		 * are not in M3 state but they are functional. So just ignore
+		 * the MHI state while resuming.
+		 */
+		ret = mhi_pm_resume_force(ab_pci->mhi_ctrl);
 		break;
 	case ATH11K_MHI_TRIGGER_RDDM:
 		ret = mhi_force_rddm_mode(ab_pci->mhi_ctrl);

include/linux/mhi.h

···
 int mhi_pm_resume(struct mhi_controller *mhi_cntrl);
 
 /**
+ * mhi_pm_resume_force - Force resume MHI from suspended state
+ * @mhi_cntrl: MHI controller
+ *
+ * Resume the device irrespective of its MHI state. As per the MHI spec, devices
+ * has to be in M3 state during resume. But some devices seem to be in a
+ * different MHI state other than M3 but they continue working fine if allowed.
+ * This API is intented to be used for such devices.
+ *
+ * Return: 0 if the resume succeeds, a negative error code otherwise
+ */
+int mhi_pm_resume_force(struct mhi_controller *mhi_cntrl);
+
+/**
  * mhi_download_rddm_image - Download ramdump image from device for
  *                           debugging purpose.
  * @mhi_cntrl: MHI controller