[PATCH v2 2/2] PCI/pwrctl: put the bus rescan on a different thread

[Bartosz Golaszewski <brgl@bgdev.pl>]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

If we trigger the bus rescan from sysfs, we'll try to lock the PCI
rescan mutex recursively and deadlock - the platform device will be
populated and probed on the same thread that handles the sysfs write.

Add a workqueue to the pwrctl code on which we schedule the rescan for
controlled PCI devices. While at it: add a new interface for
initializing the pwrctl context where we'd now assign the parent device
address and initialize the workqueue.

Fixes: 4565d2652a37 ("PCI/pwrctl: Add PCI power control core code")
Reported-by: Konrad Dybcio <konradybcio@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/pci/pwrctl/core.c              | 26 +++++++++++++++++++++++---
 drivers/pci/pwrctl/pci-pwrctl-pwrseq.c |  2 +-
 include/linux/pci-pwrctl.h             |  3 +++
 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/pwrctl/core.c b/drivers/pci/pwrctl/core.c
index feca26ad2f6a..01d913b60316 100644
--- a/drivers/pci/pwrctl/core.c
+++ b/drivers/pci/pwrctl/core.c
@@ -48,6 +48,28 @@ static int pci_pwrctl_notify(struct notifier_block *nb, unsigned long action,
 	return NOTIFY_DONE;
 }
 
+static void rescan_work_func(struct work_struct *work)
+{
+	struct pci_pwrctl *pwrctl = container_of(work, struct pci_pwrctl, work);
+
+	pci_lock_rescan_remove();
+	pci_rescan_bus(to_pci_dev(pwrctl->dev->parent)->bus);
+	pci_unlock_rescan_remove();
+}
+
+/**
+ * pci_pwrctl_init() - Initialize the PCI power control context struct
+ *
+ * @pwrctl: PCI power control data
+ * @dev: Parent device
+ */
+void pci_pwrctl_init(struct pci_pwrctl *pwrctl, struct device *dev)
+{
+	pwrctl->dev = dev;
+	INIT_WORK(&pwrctl->work, rescan_work_func);
+}
+EXPORT_SYMBOL_GPL(pci_pwrctl_init);
+
 /**
  * pci_pwrctl_device_set_ready() - Notify the pwrctl subsystem that the PCI
  * device is powered-up and ready to be detected.
@@ -74,9 +96,7 @@ int pci_pwrctl_device_set_ready(struct pci_pwrctl *pwrctl)
 	if (ret)
 		return ret;
 
-	pci_lock_rescan_remove();
-	pci_rescan_bus(to_pci_dev(pwrctl->dev->parent)->bus);
-	pci_unlock_rescan_remove();
+	schedule_work(&pwrctl->work);
 
 	return 0;
 }
diff --git a/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c b/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c
index c7a113a76c0c..f07758c9edad 100644
--- a/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c
+++ b/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c
@@ -50,7 +50,7 @@ static int pci_pwrctl_pwrseq_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	data->ctx.dev = dev;
+	pci_pwrctl_init(&data->ctx, dev);
 
 	ret = devm_pci_pwrctl_device_set_ready(dev, &data->ctx);
 	if (ret)
diff --git a/include/linux/pci-pwrctl.h b/include/linux/pci-pwrctl.h
index 45e9cfe740e4..0d23dddf59ec 100644
--- a/include/linux/pci-pwrctl.h
+++ b/include/linux/pci-pwrctl.h
@@ -7,6 +7,7 @@
 #define __PCI_PWRCTL_H__
 
 #include <linux/notifier.h>
+#include <linux/workqueue.h>
 
 struct device;
 struct device_link;
@@ -41,8 +42,10 @@ struct pci_pwrctl {
 	/* Private: don't use. */
 	struct notifier_block nb;
 	struct device_link *link;
+	struct work_struct work;
 };
 
+void pci_pwrctl_init(struct pci_pwrctl *pwrctl, struct device *dev);
 int pci_pwrctl_device_set_ready(struct pci_pwrctl *pwrctl);
 void pci_pwrctl_device_unset_ready(struct pci_pwrctl *pwrctl);
 int devm_pci_pwrctl_device_set_ready(struct device *dev,
-- 
2.43.0