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Subject[RFC PATCH 1/1] usb: dwc3: of-simple: Add extcon support
Date
Add optional extcon notifier support to enable the hotplug / unplug of
the underlying PHY layer devices.

If supported, the Device Tree (DT) node for the device should include an
"extcon" property which is a phandle to an extcon DT node.

This patch is an effort to incorporate the equivalent support from the
Rockchip dwc3 driver implementation from Chrome OS [1] to the mainline.

[1] : https://chromium.googlesource.com/chromiumos/third_party/kernel/
+/refs/heads/chromeos-4.4/drivers/usb/dwc3/dwc3-rockchip.c

Cc: Benson Leung <bleung@chromium.org>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Prashant Malani <pmalani@chromium.org>
---
drivers/usb/dwc3/dwc3-of-simple.c | 149 +++++++++++++++++++++++++++++-
1 file changed, 146 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/dwc3/dwc3-of-simple.c b/drivers/usb/dwc3/dwc3-of-simple.c
index e64754be47b4..28bde27cd1f9 100644
--- a/drivers/usb/dwc3/dwc3-of-simple.c
+++ b/drivers/usb/dwc3/dwc3-of-simple.c
@@ -11,6 +11,7 @@
* by Subbaraya Sundeep Bhatta <subbaraya.sundeep.bhatta@xilinx.com>
*/

+#include <linux/extcon.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
@@ -29,8 +30,117 @@ struct dwc3_of_simple {
struct reset_control *resets;
bool pulse_resets;
bool need_reset;
+ struct extcon_dev *edev;
+ struct notifier_block nb;
+ struct work_struct work;
+ /* Denotes whether child devices have been populated. */
+ bool populated;
+ bool suspended;
+ spinlock_t suspend_lock;
};

+static int dwc3_of_simple_populate(struct dwc3_of_simple *simple)
+{
+ struct device *dev = simple->dev;
+ struct device_node *np = dev->of_node;
+ int ret;
+
+ ret = of_platform_populate(np, NULL, NULL, dev);
+ if (ret) {
+ dev_err(dev, "Failed to populate dwc3 devices.\n");
+ return ret;
+ }
+ simple->populated = true;
+ return 0;
+}
+
+static void dwc3_of_simple_depopulate(struct dwc3_of_simple *simple)
+{
+ if (simple->populated) {
+ of_platform_depopulate(simple->dev);
+ simple->populated = false;
+ }
+}
+
+static void dwc3_of_simple_work(struct work_struct *work)
+{
+ struct dwc3_of_simple *simple = container_of(work,
+ struct dwc3_of_simple, work);
+ struct extcon_dev *edev = simple->edev;
+
+ if (extcon_get_state(edev, EXTCON_USB_HOST) > 0) {
+ if (simple->populated)
+ return;
+
+ dwc3_of_simple_populate(simple);
+ } else {
+ if (!simple->populated)
+ return;
+
+ dwc3_of_simple_depopulate(simple);
+ }
+}
+
+static int dwc3_of_simple_notifier(struct notifier_block *nb,
+ unsigned long event, void *ptr)
+{
+ struct dwc3_of_simple *simple = container_of(nb, struct dwc3_of_simple,
+ nb);
+ unsigned long flags;
+
+ spin_lock_irqsave(&simple->suspend_lock, flags);
+ if (!simple->suspended)
+ schedule_work(&simple->work);
+ spin_unlock_irqrestore(&simple->suspend_lock, flags);
+
+ return NOTIFY_OK;
+}
+
+static int dwc3_of_simple_extcon_register(struct dwc3_of_simple *simple)
+{
+ struct device *dev = simple->dev;
+ struct extcon_dev *edev;
+ int ret;
+
+ edev = extcon_get_edev_by_phandle(dev, 0);
+ if (IS_ERR(edev)) {
+ /* The extcon property is optional. */
+ if (PTR_ERR(edev) == -ENODEV)
+ return 0;
+ if (PTR_ERR(edev) != -EPROBE_DEFER)
+ dev_err(dev, "Couldn't get extcon device.\n");
+ return PTR_ERR(edev);
+ }
+
+ INIT_WORK(&simple->work, dwc3_of_simple_work);
+
+ simple->nb.notifier_call = dwc3_of_simple_notifier;
+ ret = devm_extcon_register_notifier(dev, edev, EXTCON_USB_HOST,
+ &simple->nb);
+ if (ret < 0) {
+ dev_err(dev, "Failed to register notifier.\n");
+ return ret;
+ }
+
+ simple->edev = edev;
+
+ return 0;
+}
+
+static void dwc3_of_simple_extcon_unregister(struct dwc3_of_simple *simple)
+{
+ if (!simple->edev)
+ return;
+
+ /*
+ * We explicitly unregister the notifier to prevent races with
+ * the of_depopulate() call in remove().
+ */
+ devm_extcon_unregister_notifier(simple->dev, simple->edev,
+ EXTCON_USB_HOST, &simple->nb);
+ cancel_work_sync(&simple->work);
+}
+
static int dwc3_of_simple_probe(struct platform_device *pdev)
{
struct dwc3_of_simple *simple;
@@ -47,6 +157,8 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)
platform_set_drvdata(pdev, simple);
simple->dev = dev;

+ spin_lock_init(&simple->suspend_lock);
+
/*
* Some controllers need to toggle the usb3-otg reset before trying to
* initialize the PHY, otherwise the PHY times out.
@@ -87,9 +199,24 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)
if (ret)
goto err_resetc_assert;

- ret = of_platform_populate(np, NULL, NULL, dev);
- if (ret)
+ ret = dwc3_of_simple_extcon_register(simple);
+ if (ret < 0) {
+ dev_warn(dev, "No extcon device found, err: %d\n", ret);
goto err_clk_put;
+ }
+
+ if (!simple->edev) {
+ ret = dwc3_of_simple_populate(simple);
+ if (ret)
+ goto err_clk_put;
+ } else {
+ /*
+ * Populate through worker to avoid race conditions against
+ * action scheduled through notifier.
+ */
+ if (extcon_get_state(simple->edev, EXTCON_USB_HOST) > 0)
+ schedule_work(&simple->work);
+ }

pm_runtime_set_active(dev);
pm_runtime_enable(dev);
@@ -112,7 +239,8 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)

static void __dwc3_of_simple_teardown(struct dwc3_of_simple *simple)
{
- of_platform_depopulate(simple->dev);
+ dwc3_of_simple_extcon_unregister(simple);
+ dwc3_of_simple_depopulate(simple);

clk_bulk_disable_unprepare(simple->num_clocks, simple->clks);
clk_bulk_put_all(simple->num_clocks, simple->clks);
@@ -163,6 +291,13 @@ static int __maybe_unused dwc3_of_simple_runtime_resume(struct device *dev)
static int __maybe_unused dwc3_of_simple_suspend(struct device *dev)
{
struct dwc3_of_simple *simple = dev_get_drvdata(dev);
+ unsigned long flags;
+
+ spin_lock_irqsave(&simple->suspend_lock, flags);
+ simple->suspended = true;
+ spin_unlock_irqrestore(&simple->suspend_lock, flags);
+
+ cancel_work_sync(&simple->work);

if (simple->need_reset)
reset_control_assert(simple->resets);
@@ -173,10 +308,18 @@ static int __maybe_unused dwc3_of_simple_suspend(struct device *dev)
static int __maybe_unused dwc3_of_simple_resume(struct device *dev)
{
struct dwc3_of_simple *simple = dev_get_drvdata(dev);
+ unsigned long flags;

if (simple->need_reset)
reset_control_deassert(simple->resets);

+ spin_lock_irqsave(&simple->suspend_lock, flags);
+ simple->suspended = false;
+ spin_unlock_irqrestore(&simple->suspend_lock, flags);
+
+ if (simple->edev)
+ schedule_work(&simple->work);
+
return 0;
}

--
2.27.0.rc0.183.gde8f92d652-goog
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