[PATCH v2] usb: dwc3: core: Fix timeout check

[Varadarajan Narayanan]

dwc3_core_init loops 'timeout' times to check if the IP block is out
of reset using 'while (timeout--)'. If there is some issue and
the block doesn't come out of reset, the loop will run till
'timeout' becomes zero and the post decrement operator would set
timeout to 0xffffffff. Though the IP block is not out reset, the
subsequent if check 'if !timeout' would fail as timeout is not
equal to zero and the function proceeds with the initialization.

Use poll API instead to resolve this.

Tested-By: Varadarajan Narayanan <quic_varada at quicinc.com>
Signed-off-by: Varadarajan Narayanan <quic_varada at quicinc.com>
---
v2: * Use poll API and remove the timeout variable based loop as
      suggested by 'Marek Vasut'
    * Drop 'Reviewed-by: Neil Armstrong' as the patch has taken
      a very different shape
---
 drivers/usb/dwc3/core.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index a35b8c2f64..847fa1f82c 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -23,6 +23,7 @@
 #include <linux/delay.h>
 #include <linux/dma-mapping.h>
 #include <linux/err.h>
+#include <linux/iopoll.h>
 #include <linux/ioport.h>
 #include <dm.h>
 #include <generic-phy.h>
@@ -587,7 +588,6 @@ static void dwc3_set_incr_burst_type(struct dwc3 *dwc)
  */
 static int dwc3_core_init(struct dwc3 *dwc)
 {
-	unsigned long		timeout;
 	u32			hwparams4 = dwc->hwparams.hwparams4;
 	u32			reg;
 	int			ret;
@@ -610,15 +610,11 @@ static int dwc3_core_init(struct dwc3 *dwc)
 	}
 
 	/* issue device SoftReset too */
-	timeout = 5000;
 	dwc3_writel(dwc->regs, DWC3_DCTL, DWC3_DCTL_CSFTRST);
-	while (timeout--) {
-		reg = dwc3_readl(dwc->regs, DWC3_DCTL);
-		if (!(reg & DWC3_DCTL_CSFTRST))
-			break;
-	};
-
-	if (!timeout) {
+	ret = read_poll_timeout(dwc3_readl, reg,
+				!(reg & DWC3_DCTL_CSFTRST),
+				1, 5000, dwc->regs, DWC3_DCTL);
+	if (ret) {
 		dev_err(dwc->dev, "Reset Timed Out\n");
 		ret = -ETIMEDOUT;
 		goto err0;
-- 
2.34.1