Re: [PATCH v1] usb: dwc3: core: Fix timeout check

[Marek Vasut]

On 1/10/25 8:43 AM, Varadarajan Narayanan wrote:
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.
Make this a pre decrement to address this.

Signed-off-by: Varadarajan Narayanan <quic_var...@quicinc.com>
Does the following patch work too ? It removes all the fragile 
open-coded polling

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index a35b8c2f646..7e7017d4be7 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -29,6 +29,7 @@
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
 #include <linux/bitfield.h>
+#include <linux/iopoll.h>
 #include <linux/math64.h>
 #include <linux/time.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;
@@ -610,17 +610,12 @@ 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;
        }