xtensa: rework noMMU cache attributes initialization

Marking default memory region as cached is not always sufficient and is
not flexible. Allow specifying cache attributes for the whole memory
address space with new config entry MEMMAP_CACHEATTR. Apply it after
cache initialization.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/Kconfig

@@ -249,6 +249,23 @@ config INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
 
 	  If in doubt, say Y.
 
+config MEMMAP_CACHEATTR
+	hex "Cache attributes for the memory address space"
+	depends on !MMU
+	default 0x22222222
+	help
+	  These cache attributes are set up for noMMU systems. Each hex digit
+	  specifies cache attributes for the corresponding 512MB memory
+	  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).
+
 config KSEG_PADDR
 	hex "Physical address of the KSEG mapping"
 	depends on INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX && MMU

arch/xtensa/configs/nommu_kc705_defconfig

@@ -33,6 +33,7 @@ CONFIG_XTENSA_VARIANT_CUSTOM_NAME="de212"
 # CONFIG_XTENSA_VARIANT_MMU is not set
 CONFIG_XTENSA_UNALIGNED_USER=y
 CONFIG_PREEMPT=y
+CONFIG_MEMMAP_CACHEATTR=0xfff2442f
 # CONFIG_PCI is not set
 CONFIG_XTENSA_PLATFORM_XTFPGA=y
 CONFIG_CMDLINE_BOOL=y

arch/xtensa/include/asm/initialize_mmu.h

@@ -177,36 +177,36 @@
 #endif /* defined(CONFIG_MMU) && XCHAL_HAVE_PTP_MMU &&
 	  XCHAL_HAVE_SPANNING_WAY */
 
-#if !defined(CONFIG_MMU) && XCHAL_HAVE_TLBS && \
-		(XCHAL_DCACHE_SIZE || XCHAL_ICACHE_SIZE)
-	/* Enable data and instruction cache in the DEFAULT_MEMORY region
-	 * if the processor has DTLB and ITLB.
-	 */
+	.endm
+
+	.macro	initialize_cacheattr
 
-	movi	a5, PLATFORM_DEFAULT_MEM_START | XCHAL_SPANNING_WAY
+#if !defined(CONFIG_MMU) && XCHAL_HAVE_TLBS
+#if CONFIG_MEMMAP_CACHEATTR == 0x22222222 && XCHAL_HAVE_PTP_MMU
+#error Default MEMMAP_CACHEATTR of 0x22222222 does not work with full MMU.
+#endif
+
+	movi	a5, XCHAL_SPANNING_WAY
 	movi	a6, ~_PAGE_ATTRIB_MASK
-	movi	a7, CA_WRITEBACK
+	movi	a4, CONFIG_MEMMAP_CACHEATTR
 	movi	a8, 0x20000000
-	movi	a9, PLATFORM_DEFAULT_MEM_SIZE
-	j	2f
 1:
-	sub	a9, a9, a8
-2:
-#if XCHAL_DCACHE_SIZE
 	rdtlb1	a3, a5
+	xor	a3, a3, a4
 	and	a3, a3, a6
-	or	a3, a3, a7
+	xor	a3, a3, a4
 	wdtlb	a3, a5
-#endif
-#if XCHAL_ICACHE_SIZE
-	ritlb1	a4, a5
-	and	a4, a4, a6
-	or	a4, a4, a7
-	witlb	a4, a5
-#endif
+	ritlb1	a3, a5
+	xor	a3, a3, a4
+	and	a3, a3, a6
+	xor	a3, a3, a4
+	witlb	a3, a5
+
 	add	a5, a5, a8
-	bltu	a8, a9, 1b
+	srli	a4, a4, 4
+	bgeu	a5, a8, 1b
 
+	isync
 #endif
 
 	.endm

arch/xtensa/kernel/head.S

@@ -181,6 +181,8 @@ ENTRY(_startup)
 
 	isync
 
+	initialize_cacheattr
+
 #ifdef CONFIG_HAVE_SMP
 	movi	a2, CCON	# MX External Register to Configure Cache
 	movi	a3, 1