parisc: Check for valid stride size for cache flushes

Report if the calculated cache stride size is zero, otherwise the cache
flushing routine will never finish and hang the machine.
This can be reproduced with a testcase in qemu, where the firmware reports
wrong cache values.
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/kernel/cache.c

@@ -264,6 +264,10 @@ parisc_cache_init(void)
 	icache_stride = CAFL_STRIDE(cache_info.ic_conf);
 #undef CAFL_STRIDE
 
+	/* stride needs to be non-zero, otherwise cache flushes will not work */
+	WARN_ON(cache_info.dc_size && dcache_stride == 0);
+	WARN_ON(cache_info.ic_size && icache_stride == 0);
+
 	if ((boot_cpu_data.pdc.capabilities & PDC_MODEL_NVA_MASK) ==
 						PDC_MODEL_NVA_UNSUPPORTED) {
 		printk(KERN_WARNING "parisc_cache_init: Only equivalent aliasing supported!\n");