[PATCH] usb: dwc3: dwc3-octeon: Verify clock divider

[Ladislav Michl <oss-lists@triops.cz>]

From: Ladislav Michl <ladis@linux-mips.org>

Although valid USB clock divider will be calculated for all valid
Octeon core frequencies, make code formally correct limiting
divider not to be greater that 7 so it fits into H_CLKDIV_SEL
field.

Signed-off-by: Ladislav Michl <ladis@linux-mips.org>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Closes: https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20230808/testrun/18882876/suite/build/test/gcc-8-cavium_octeon_defconfig/log
---
 Greg, if you want to resent whole serie, just drop me a note.
 Otherwise, this patch is meant to be applied on to of it.
 Thank you.

 drivers/usb/dwc3/dwc3-octeon.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc3/dwc3-octeon.c b/drivers/usb/dwc3/dwc3-octeon.c
index 6f47262a117a..73bdcebf465c 100644
--- a/drivers/usb/dwc3/dwc3-octeon.c
+++ b/drivers/usb/dwc3/dwc3-octeon.c
@@ -251,11 +251,11 @@ static int dwc3_octeon_get_divider(void)
 	while (div < ARRAY_SIZE(clk_div)) {
 		uint64_t rate = octeon_get_io_clock_rate() / clk_div[div];
 		if (rate <= 300000000 && rate >= 150000000)
-			break;
+			return div;
 		div++;
 	}
 
-	return div;
+	return -EINVAL;
 }
 
 static int dwc3_octeon_setup(struct dwc3_octeon *octeon,
@@ -289,6 +289,10 @@ static int dwc3_octeon_setup(struct dwc3_octeon *octeon,
 
 	/* Step 4b: Select controller clock frequency. */
 	div = dwc3_octeon_get_divider();
+	if (div < 0) {
+		dev_err(dev, "clock divider invalid\n");
+		return div;
+	}
 	val = dwc3_octeon_readq(uctl_ctl_reg);
 	val &= ~USBDRD_UCTL_CTL_H_CLKDIV_SEL;
 	val |= FIELD_PREP(USBDRD_UCTL_CTL_H_CLKDIV_SEL, div);
-- 
2.39.2