Since commit a035d552a93b ("Makefile: Globally enable fall-through
warning"), cavium_octeon_defconfig builds fail with

In file included from
arch/mips/cavium-octeon/octeon-usb.c:12:
arch/mips/cavium-octeon/octeon-usb.c: In function 'dwc3_octeon_clocks_start':
include/linux/device.h:1499:2: error: this statement may fall through
  _dev_err(dev, dev_fmt(fmt), ##__VA_ARGS__)
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/mips/cavium-octeon/octeon-usb.c:399:3: note:
			in expansion of macro 'dev_err'
  dev_err(dev, "Invalid ref_clk %u, using 100000000 instead\n",
  ^~~~~~~
arch/mips/cavium-octeon/octeon-usb.c:401:2: note: here
  case 100000000:
  ^~~~~~~

Mark the switch case to expect fall through.

Cc: Gustavo A. R. Silva <redacted>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 arch/mips/cavium-octeon/octeon-usb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/mips/cavium-octeon/octeon-usb.c b/arch/mips/cavium-octeon/octeon-usb.c
index 1f730ded5224..8a16ab37aa11 100644
--- a/arch/mips/cavium-octeon/octeon-usb.c
+++ b/arch/mips/cavium-octeon/octeon-usb.c

@@ -398,6 +398,7 @@ static int dwc3_octeon_clocks_start(struct device *dev, u64 base)
 	default:
 		dev_err(dev, "Invalid ref_clk %u, using 100000000 instead\n",
 			clock_rate);
+		/* Fall through */
 	case 100000000:
 		mpll_mul = 0x19;
 		if (ref_clk_sel < 2)

-- 
2.7.4