Re: [PATCH v2 10/10] usb: dwc2/gadget: rework suspend/resume code to correctly restore gadget state

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Hello,

On 2014-10-25 03:16, Paul Zimmerman wrote:
From: Marek Szyprowski [mailto:m.szyprowski@xxxxxxxxxxx]
Sent: Monday, October 20, 2014 3:46 AM

Suspend/resume code assumed that the gadget was always enabled and
connected to usb bus. This means that the actual state of the gadget
(soft-enabled/disabled or connected/disconnected) was not correctly
preserved on suspend/resume cycle. This patch fixes this issue.

Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
  drivers/usb/dwc2/core.h   |  4 +++-
  drivers/usb/dwc2/gadget.c | 43 +++++++++++++++++++++++++++----------------
  2 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h
index bf015ab3b44c..3648b76a18b4 100644
--- a/drivers/usb/dwc2/core.h
+++ b/drivers/usb/dwc2/core.h
@@ -210,7 +210,9 @@ struct s3c_hsotg {
  	u8                      ctrl_buff[8];

  	struct usb_gadget       gadget;
-	unsigned int            setup;
+	unsigned int            setup:1;
+	unsigned int		connected:1;
+	unsigned int		enabled:1;
  	unsigned long           last_rst;
  	struct s3c_hsotg_ep     *eps;
  };
diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
index 0d34cfc71bfb..c6c6cf982c90 100644
--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -2925,6 +2925,8 @@ static int s3c_hsotg_udc_start(struct usb_gadget *gadget,
  	spin_lock_irqsave(&hsotg->lock, flags);
  	s3c_hsotg_init(hsotg);
  	s3c_hsotg_core_init_disconnected(hsotg);
+	hsotg->enabled = 1;
+	hsotg->connected = 0;
  	spin_unlock_irqrestore(&hsotg->lock, flags);

  	dev_info(hsotg->dev, "bound driver %s\n", driver->driver.name);
@@ -2961,6 +2963,8 @@ static int s3c_hsotg_udc_stop(struct usb_gadget *gadget,

  	hsotg->driver = NULL;
  	hsotg->gadget.speed = USB_SPEED_UNKNOWN;
+	hsotg->enabled = 0;
+	hsotg->connected = 0;

  	spin_unlock_irqrestore(&hsotg->lock, flags);

@@ -2999,11 +3003,14 @@ static int s3c_hsotg_pullup(struct usb_gadget *gadget, int is_on)
  	dev_dbg(hsotg->dev, "%s: is_on: %d\n", __func__, is_on);

  	spin_lock_irqsave(&hsotg->lock, flags);
+
  	if (is_on) {
  		clk_enable(hsotg->clk);
+		hsotg->connected = 1;
  		s3c_hsotg_core_connect(hsotg);
  	} else {
  		s3c_hsotg_core_disconnect(hsotg);
+		hsotg->connected = 0;
  		clk_disable(hsotg->clk);
  	}

@@ -3652,16 +3659,18 @@ static int s3c_hsotg_suspend(struct platform_device *pdev, pm_message_t state)
  		dev_info(hsotg->dev, "suspending usb gadget %s\n",
  			 hsotg->driver->driver.name);

-	spin_lock_irqsave(&hsotg->lock, flags);
-	s3c_hsotg_core_disconnect(hsotg);
-	s3c_hsotg_disconnect(hsotg);
-	hsotg->gadget.speed = USB_SPEED_UNKNOWN;
-	spin_unlock_irqrestore(&hsotg->lock, flags);
+	if (hsotg->enabled) {
Hmm. Are you sure it's safe to check ->enabled outside of the spinlock?
What happens if s3c_hsotg_udc_stop() runs right after this, before the
spinlock is taken, and disables stuff? Sure, it's a tiny window, but
still...

This code is called only in system suspend path, when userspace has been already frozen. udc_stop() can be called only as a result of userspace action, so it is imho safe to
assume that the above code doesn't need additional locking.

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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