linux-kernel - [PATCH 27/29] bus: mhi: core: Fix device hierarchy

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Date:   Wed,  2 Dec 2020 15:11:57 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     gregkh@...uxfoundation.org
Cc:     hemantk@...eaurora.org, bbhatt@...eaurora.org,
        linux-arm-msm@...r.kernel.org, jhugo@...eaurora.org,
        linux-kernel@...r.kernel.org, loic.poulain@...aro.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH 27/29] bus: mhi: core: Fix device hierarchy

From: Loic Poulain <loic.poulain@...aro.org>

This patch fixes the hierarchical structure of MHI devices. Indeed,
MHI client devices are directly 'enumerated' from the mhi controller
and therefore must be direct descendants/children of their mhi
controller device, in accordance with the Linux Device Model.

Today both MHI clients and controller devices are at the same level,
this patch ensures that MHI controller is parent of its client devices.

The hierarchy is especially important for power management (safe
suspend/resume order). It is also useful for userspace to determine
relationship between MHI client devices and controllers.

Signed-off-by: Loic Poulain <loic.poulain@...aro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Reviewed-by: Hemant Kumar <hemantk@...eaurora.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/bus/mhi/core/debugfs.c |  4 +++-
 drivers/bus/mhi/core/init.c    | 10 +++++++++-
 drivers/bus/mhi/core/pm.c      |  4 ++--
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/bus/mhi/core/debugfs.c b/drivers/bus/mhi/core/debugfs.c
index 3a48801e01f4..7d43138ce66d 100644
--- a/drivers/bus/mhi/core/debugfs.c
+++ b/drivers/bus/mhi/core/debugfs.c
@@ -159,7 +159,9 @@ static int mhi_debugfs_devices_show(struct seq_file *m, void *d)
 		return -ENODEV;
 	}
 
-	device_for_each_child(mhi_cntrl->cntrl_dev, m, mhi_device_info_show);
+	/* Show controller and client(s) info */
+	mhi_device_info_show(&mhi_cntrl->mhi_dev->dev, m);
+	device_for_each_child(&mhi_cntrl->mhi_dev->dev, m, mhi_device_info_show);
 
 	return 0;
 }
diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index 1d6f7b6c1fcd..96cde9c0034c 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -1144,7 +1144,15 @@ struct mhi_device *mhi_alloc_device(struct mhi_controller *mhi_cntrl)
 	device_initialize(dev);
 	dev->bus = &mhi_bus_type;
 	dev->release = mhi_release_device;
-	dev->parent = mhi_cntrl->cntrl_dev;
+
+	if (mhi_cntrl->mhi_dev) {
+		/* for MHI client devices, parent is the MHI controller device */
+		dev->parent = &mhi_cntrl->mhi_dev->dev;
+	} else {
+		/* for MHI controller device, parent is the bus device (e.g. pci device) */
+		dev->parent = mhi_cntrl->cntrl_dev;
+	}
+
 	mhi_dev->mhi_cntrl = mhi_cntrl;
 	mhi_dev->dev_wake = 0;
 
diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
index a671f585ce35..681960c72d2a 100644
--- a/drivers/bus/mhi/core/pm.c
+++ b/drivers/bus/mhi/core/pm.c
@@ -504,7 +504,7 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
 	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->cntrl_dev, NULL, mhi_destroy_device);
+	device_for_each_child(&mhi_cntrl->mhi_dev->dev, NULL, mhi_destroy_device);
 
 	mutex_lock(&mhi_cntrl->pm_mutex);
 
@@ -637,7 +637,7 @@ static void mhi_pm_sys_error_transition(struct mhi_controller *mhi_cntrl)
 	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->cntrl_dev, NULL, mhi_destroy_device);
+	device_for_each_child(&mhi_cntrl->mhi_dev->dev, NULL, mhi_destroy_device);
 
 	mutex_lock(&mhi_cntrl->pm_mutex);
 
-- 
2.25.1