ARCv2: IOC: Use actual memory size to setup aperture size

vs. fixed 512M before.

But this still assumes that all of memory is under IOC which may not be
true for the SoC. Improve that later when this becomes a real issue, by
specifying this from DT.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/mm/cache.c

@@ -995,6 +995,8 @@ SYSCALL_DEFINE3(cacheflush, uint32_t, start, uint32_t, sz, uint32_t, flags)
  */
 noinline void arc_ioc_setup(void)
 {
+	unsigned int ap_sz;
+
 	/* Flush + invalidate + disable L1 dcache */
 	__dc_disable();
 
@@ -1005,8 +1007,14 @@ noinline void arc_ioc_setup(void)
 	/* IOC Aperture start: TDB: handle non default CONFIG_LINUX_LINK_BASE */
 	write_aux_reg(ARC_REG_IO_COH_AP0_BASE, 0x80000);
 
-	/* IOC Aperture size: TBD: handle different mem sizes, PAE... */
-	write_aux_reg(ARC_REG_IO_COH_AP0_SIZE, 0x11);
+	/*
+	 * IOC Aperture size:
+	 *   decoded as 2 ^ (SIZE + 2) KB: so setting 0x11 implies 512M
+	 * TBD: fix for PGU + 1GB of low mem
+	 * TBD: fix for PAE
+	 */
+	ap_sz = order_base_2(arc_get_mem_sz()/1024) - 2;
+	write_aux_reg(ARC_REG_IO_COH_AP0_SIZE, ap_sz);
 
 	write_aux_reg(ARC_REG_IO_COH_PARTIAL, 1);
 	write_aux_reg(ARC_REG_IO_COH_ENABLE, 1);