microblaze: Extend cpuinfo for support write-back caches

There is missing checking agains PVR but this is not important
for now. There are some missing checking too.
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/include/asm/cpuinfo.h

@@ -53,6 +53,7 @@ struct cpuinfo {
 	u32 dcache_write;
 	u32 dcache_line_length;
 	u32 dcache_size;
+	u32 dcache_wb;
 	unsigned long dcache_base;
 	unsigned long dcache_high;
 

arch/microblaze/kernel/cpu/cpuinfo-static.c

@@ -96,6 +96,7 @@ void __init set_cpuinfo_static(struct cpuinfo *ci, struct device_node *cpu)
 	ci->dcache_size = fcpu(cpu, "d-cache-size");
 	ci->dcache_base = fcpu(cpu, "d-cache-baseaddr");
 	ci->dcache_high = fcpu(cpu, "d-cache-highaddr");
+	ci->dcache_wb = fcpu(cpu, "xlnx,dcache-use-writeback");
 
 	ci->use_dopb = fcpu(cpu, "xlnx,d-opb");
 	ci->use_iopb = fcpu(cpu, "xlnx,i-opb");

arch/microblaze/kernel/cpu/mb.c

@@ -103,11 +103,15 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 	else
 		count += seq_printf(m, "Icache:\t\tno\n");
 
-	if (cpuinfo.use_dcache)
+	if (cpuinfo.use_dcache) {
 		count += seq_printf(m,
 				"Dcache:\t\t%ukB\n",
 				cpuinfo.dcache_size >> 10);
-	else
+		if (cpuinfo.dcache_wb)
+			count += seq_printf(m, "\t\twrite-back\n");
+		else
+			count += seq_printf(m, "\t\twrite-through\n");
+	} else
 		count += seq_printf(m, "Dcache:\t\tno\n");
 
 	count += seq_printf(m,