xtensa: implement initialize_cacheattr for MPU cores

Use CONFIG_MEMMAP_CACHEATTR to initialize MPU as described in the Xtensa
LSP RM document. Coalesce adjacent regions with the same cacheattr.
Update Kconfig help text.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/Kconfig

@@ -256,12 +256,26 @@ config MEMMAP_CACHEATTR
 	  region: bits 0..3 -- for addresses 0x00000000..0x1fffffff,
 	  bits 4..7 -- for addresses 0x20000000..0x3fffffff, and so on.
 
-	  Cache attribute values are specific for the MMU type, so e.g.
-	  for region protection MMUs: 2 is cache bypass, 4 is WB cached,
-	  1 is WT cached, f is illegal. For ful MMU: bit 0 makes it executable,
-	  bit 1 makes it writable, bits 2..3 meaning is 0: cache bypass,
-	  1: WB cache, 2: WT cache, 3: special (c and e are illegal, f is
-	  reserved).
+	  Cache attribute values are specific for the MMU type.
+	  For region protection MMUs:
+	    1: WT cached,
+	    2: cache bypass,
+	    4: WB cached,
+	    f: illegal.
+	  For ful MMU:
+	    bit 0: executable,
+	    bit 1: writable,
+	    bits 2..3:
+	      0: cache bypass,
+	      1: WB cache,
+	      2: WT cache,
+	      3: special (c and e are illegal, f is reserved).
+	  For MPU:
+	    0: illegal,
+	    1: WB cache,
+	    2: WB, no-write-allocate cache,
+	    3: WT cache,
+	    4: cache bypass.
 
 config KSEG_PADDR
 	hex "Physical address of the KSEG mapping"

arch/xtensa/include/asm/core.h

@@ -10,6 +10,10 @@
 #define XCHAL_HAVE_EXCLUSIVE 0
 #endif
 
+#ifndef XCHAL_HAVE_MPU
+#define XCHAL_HAVE_MPU 0
+#endif
+
 #ifndef XCHAL_SPANNING_WAY
 #define XCHAL_SPANNING_WAY 0
 #endif

arch/xtensa/include/asm/initialize_mmu.h

@@ -177,11 +177,42 @@
 
 	.macro	initialize_cacheattr
 
-#if !defined(CONFIG_MMU) && XCHAL_HAVE_TLBS
+#if !defined(CONFIG_MMU) && (XCHAL_HAVE_TLBS || XCHAL_HAVE_MPU)
 #if CONFIG_MEMMAP_CACHEATTR == 0x22222222 && XCHAL_HAVE_PTP_MMU
 #error Default MEMMAP_CACHEATTR of 0x22222222 does not work with full MMU.
 #endif
 
+#if XCHAL_HAVE_MPU
+	.data
+	.align	4
+.Lattribute_table:
+	.long 0x000000, 0x1fff00, 0x1ddf00, 0x1eef00
+	.long 0x006600, 0x000000, 0x000000, 0x000000
+	.long 0x000000, 0x000000, 0x000000, 0x000000
+	.long 0x000000, 0x000000, 0x000000, 0x000000
+	.previous
+
+	movi	a3, .Lattribute_table
+	movi	a4, CONFIG_MEMMAP_CACHEATTR
+	movi	a5, 1
+	movi	a6, XCHAL_MPU_ENTRIES
+	movi	a10, 0x20000000
+	movi	a11, -1
+1:
+	sub	a5, a5, a10
+	extui	a8, a4, 28, 4
+	beq	a8, a11, 2f
+	addi	a6, a6, -1
+	mov	a11, a8
+2:
+	addx4	a9, a8, a3
+	l32i	a9, a9, 0
+	or	a9, a9, a6
+	wptlb	a9, a5
+	slli	a4, a4, 4
+	bgeu	a5, a10, 1b
+
+#else
 	movi	a5, XCHAL_SPANNING_WAY
 	movi	a6, ~_PAGE_ATTRIB_MASK
 	movi	a4, CONFIG_MEMMAP_CACHEATTR
@@ -203,6 +234,7 @@
 	bgeu	a5, a8, 1b
 
 	isync
+#endif
 #endif
 
 	.endm