sfc: fix ef100 design-param checking

The handling of the RXQ/TXQ size granularity design-params had two
 problems: it had a 64-bit divide that didn't build on 32-bit platforms,
 and it could divide by zero if the NIC supplied 0 as the value of the
 design-param.  Fix both by checking for 0 and for a granularity bigger
 than our min-size; if the granularity <= EFX_MIN_DMAQ_SIZE then it fits
 in 32 bits, so we can cast it to u32 for the divide.

Reported-by: kernel test robot <[email protected]>
Signed-off-by: Edward Cree <[email protected]>
Reviewed-by: Guenter Roeck <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: ecree-solarflare

drivers/net/ethernet/sfc/ef100_nic.c

@@ -979,7 +979,8 @@ static int ef100_process_design_param(struct efx_nic *efx,
 		 * EFX_MIN_DMAQ_SIZE is divisible by GRANULARITY.
 		 * This is very unlikely to fail.
 		 */
-		if (EFX_MIN_DMAQ_SIZE % reader->value) {
+		if (!reader->value || reader->value > EFX_MIN_DMAQ_SIZE ||
+		    EFX_MIN_DMAQ_SIZE % (u32)reader->value) {
 			netif_err(efx, probe, efx->net_dev,
 				  "%s size granularity is %llu, can't guarantee safety\n",
 				  reader->type == ESE_EF100_DP_GZ_RXQ_SIZE_GRANULARITY ? "RXQ" : "TXQ",