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Subject[PATCH] usb: dwc3: gadget: don't rely on jiffies while holding spinlock
Date
__dwc3_gadget_wakeup() is called while holding a spinlock, then depends on
jiffies in order to timeout while polling the USB core for a link state
update. In the case the wakeup failed, the timeout will never happen and
will also cause the cpu to stall until rcu_preempt kicks in.

This switches to a "decrement variable and wait" timeout scheme.

Signed-off-by: Nicolas Saenz Julienne <nicolassaenzj@gmail.com>
---
drivers/usb/dwc3/gadget.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 8f8c215..d0c711f 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1433,7 +1433,7 @@ static int dwc3_gadget_get_frame(struct usb_gadget *g)

static int __dwc3_gadget_wakeup(struct dwc3 *dwc)
{
- unsigned long timeout;
+ int retries;

int ret;
u32 reg;
@@ -1484,14 +1484,16 @@ static int __dwc3_gadget_wakeup(struct dwc3 *dwc)
}

/* poll until Link State changes to ON */
- timeout = jiffies + msecs_to_jiffies(100);
+ retries = 20000;

- while (!time_after(jiffies, timeout)) {
+ while (retries--) {
reg = dwc3_readl(dwc->regs, DWC3_DSTS);

/* in HS, means ON */
if (DWC3_DSTS_USBLNKST(reg) == DWC3_LINK_STATE_U0)
break;
+
+ udelay(5);
}

if (DWC3_DSTS_USBLNKST(reg) != DWC3_LINK_STATE_U0) {
--
2.7.4
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