bcm53xx: switch back to standalone ASM entry flushing cache

Over a year ago in a commit ac96a1665ac7 ("bcm53xx: update Disable MMU
and Dcache during decompression") we switched to Florian's patch for
workarounding CFE bug. The main difference was using a part of existing
__armv7_mmu_cache_flush instead of implementing flushing separately.

This worked well for Northstar devices but doesn't work for BCM53573 as
these devices simply don't start booting with Florian's patch. It's
because of the ldmfd ASM instruction in the __armv7_mmu_cache_flush.

So this commit switches back to using standalone implementation. This
time instead of copying Broadcom's copy of cache-v7.S, we just make a
copy of the original file on our own. Unfortunately we can't cross-dir
compile cache-v7.S from ../../mm/ as that one also adds __INITDATA with
define_cache_functions v7 which would just trigger
> Error: unrecognized/unsupported machine ID (r1 = 0x0000007f).

The only real change Broadcom did in copied .S file was modifying mcr
instruction to use c6 instead of c14. It isn't clear to me if we really
need it, but let's use it for now.

By the way we also update commit message of the
[PATCH] ARM: BCM5301X: Disable MMU and Dcache during decompression

This makes kernel booting on BCM53573 successfully.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

2 files changed, 100 insertions, 86 deletions

diff --git a/target/linux/bcm53xx/patches-4.4/300-ARM-BCM5301X-Disable-MMU-and-Dcache-during-decompres.patch b/target/linux/bcm53xx/patches-4.4/300-ARM-BCM5301X-Disable-MMU-and-Dcache-during-decompres.patch
new file mode 100644
index 0000000000..5dba027725
--- /dev/null
+++ b/target/linux/bcm53xx/patches-4.4/300-ARM-BCM5301X-Disable-MMU-and-Dcache-during-decompres.patch
@@ -0,0 +1,100 @@
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
+Date: Wed, 24 Sep 2014 22:14:07 +0200
+Subject: [PATCH] ARM: BCM5301X: Disable MMU and Dcache during decompression
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Broadcom devices have broken CFE (bootloader) that leaves hardware in an
+invalid state. It causes problems with booting Linux. On Northstar
+devices kernel was randomly hanging in ~25% of tries during early init.
+Hangs used to happen at random places in the start_kernel. On BCM53573
+kernel doesn't even seem to start booting.
+
+To workaround this problem we need to do following very early:
+1) Clear 2 following bits in the SCTLR register:
+#define CR_M    (1 << 0)        /* MMU enable */
+#define CR_C    (1 << 2)        /* Dcache enable */
+2) Flush the whole D-cache
+3) Disable L2 cache
+
+Unfortunately this patch is not upstreamable as it does above things
+unconditionally. We can't check if we are running on Broadcom platform
+in any safe way and doing such hacks with ARCH_MULTI_V7 is unacceptable
+as it could break other devices support.
+
+Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
+---
+
+--- a/arch/arm/boot/compressed/Makefile
++++ b/arch/arm/boot/compressed/Makefile
+@@ -31,6 +31,11 @@ ifeq ($(CONFIG_ARCH_ACORN),y)
+ OBJS		+= ll_char_wr.o font.o
+ endif
+ 
++ifeq ($(CONFIG_ARCH_BCM_5301X),y)
++OBJS		+= head-bcm_5301x-mpcore.o
++OBJS		+= cache-v7-min.o
++endif
++
+ ifeq ($(CONFIG_ARCH_SA1100),y)
+ OBJS		+= head-sa1100.o
+ endif
+--- /dev/null
++++ b/arch/arm/boot/compressed/head-bcm_5301x-mpcore.S
+@@ -0,0 +1,37 @@
++/*
++ *
++ * Platform specific tweaks.  This is merged into head.S by the linker.
++ *
++ */
++
++#include <linux/linkage.h>
++#include <asm/assembler.h>
++#include <asm/cp15.h>
++
++		.section        ".start", "ax"
++
++/*
++ * This code section is spliced into the head code by the linker
++ */
++
++__plat_uncompress_start:
++
++	@ Preserve r8/r7 i.e. kernel entry values
++	mov	r12, r8
++
++	@ Clear MMU enable and Dcache enable bits
++	mrc	p15, 0, r0, c1, c0, 0		@ Read SCTLR
++	bic	r0, #CR_C|CR_M
++	mcr	p15, 0, r0, c1, c0, 0		@ Write SCTLR
++	nop
++
++	@ Call the cache invalidation routine
++	bl	v7_flush_dcache_all
++	nop
++	mov	r0,#0
++	ldr	r3, =0x19022000			@ L2 cache controller, control reg
++	str	r0, [r3, #0x100]		@ Disable L2 cache
++	nop
++
++	@ Restore
++	mov	r8, r12
+--- a/arch/arm/boot/compressed/cache-v7-min.S
++++ b/arch/arm/boot/compressed/cache-v7-min.S
+@@ -51,7 +51,7 @@ loop2:
+ loop3:
+ 	orr	r11, r10, r9, lsl r5		@ factor way and cache number into r11
+ 	orr	r11, r11, r7, lsl r2		@ factor index number into r11
+-	mcr	p15, 0, r11, c7, c14, 2		@ clean & invalidate by set/way
++	mcr     p15, 0, r11, c7, c6, 2		@ Invalidate line
+ 	subs	r9, r9, #1			@ decrement the way
+ 	bge	loop3
+ 	subs	r7, r7, #1			@ decrement the index
+@@ -63,5 +63,6 @@ skip:
+ finished:
+ 	mov	r10, #0				@ swith back to cache level 0
+ 	mcr	p15, 2, r10, c0, c0, 0		@ select current cache level in cssr
++	dsb
+ 	isb
+ 	mov	pc, lr
diff --git a/target/linux/bcm53xx/patches-4.4/300-ARM-BCM5301X-Disable-MMU-and-Dcache-for-decompression.patch b/target/linux/bcm53xx/patches-4.4/300-ARM-BCM5301X-Disable-MMU-and-Dcache-for-decompression.patch
deleted file mode 100644
index 62bda2e830..0000000000
--- a/target/linux/bcm53xx/patches-4.4/300-ARM-BCM5301X-Disable-MMU-and-Dcache-for-decompression.patch
+++ /dev/null
@@ -1,86 +0,0 @@
-From: Florian Fainelli <f.fainelli@gmail.com>
-Subject: [PATCH] ARM: BCM5301x: Disable MMU and Dcache during decompression
-Date: Tue, 14 Jul 2015 16:12:08 -0700
-
-Use the existing __armv7_mmu_cache_flush() to perform the cache flush
-since this does what we are after.
-
-Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
----
- arch/arm/boot/compressed/Makefile                |  4 +++
- arch/arm/boot/compressed/head-bcm_5301x-mpcore.S | 37 ++++++++++++++++++++++++
- arch/arm/boot/compressed/head.S                  |  2 ++
- 3 files changed, 43 insertions(+)
- create mode 100644 arch/arm/boot/compressed/head-bcm_5301x-mpcore.S
-
---- a/arch/arm/boot/compressed/Makefile
-+++ b/arch/arm/boot/compressed/Makefile
-@@ -31,6 +31,10 @@ ifeq ($(CONFIG_ARCH_ACORN),y)
- OBJS		+= ll_char_wr.o font.o
- endif
- 
-+ifeq ($(CONFIG_ARCH_BCM_5301X),y)
-+OBJS		+= head-bcm_5301x-mpcore.o
-+endif
-+
- ifeq ($(CONFIG_ARCH_SA1100),y)
- OBJS		+= head-sa1100.o
- endif
---- /dev/null
-+++ b/arch/arm/boot/compressed/head-bcm_5301x-mpcore.S
-@@ -0,0 +1,37 @@
-+/*
-+ *
-+ * Platform specific tweaks.  This is merged into head.S by the linker.
-+ *
-+ */
-+
-+#include <linux/linkage.h>
-+#include <asm/assembler.h>
-+#include <asm/cp15.h>
-+
-+		.section        ".start", "ax"
-+
-+/*
-+ * This code section is spliced into the head code by the linker
-+ */
-+
-+__plat_uncompress_start:
-+
-+	@ Preserve r8/r7 i.e. kernel entry values
-+	mov	r12, r8
-+
-+	@ Clear MMU enable and Dcache enable bits
-+	mrc	p15, 0, r0, c1, c0, 0		@ Read SCTLR
-+	bic	r0, #CR_C|CR_M
-+	mcr	p15, 0, r0, c1, c0, 0		@ Write SCTLR
-+	nop
-+
-+	@ Call the cache invalidation routine
-+	bl	__armv7_mmu_cache_flush_fn
-+	nop
-+	mov	r0,#0
-+	ldr	r3, =0x19022000			@ L2 cache controller, control reg
-+	str	r0, [r3, #0x100]		@ Disable L2 cache
-+	nop
-+
-+	@ Restore
-+	mov	r8, r12
---- a/arch/arm/boot/compressed/head.S
-+++ b/arch/arm/boot/compressed/head.S
-@@ -1152,6 +1152,7 @@ __armv7_mmu_cache_flush:
- hierarchical:
- 		mcr	p15, 0, r10, c7, c10, 5	@ DMB
- 		stmfd	sp!, {r0-r7, r9-r11}
-+ENTRY(__armv7_mmu_cache_flush_fn)
- 		mrc	p15, 1, r0, c0, c0, 1	@ read clidr
- 		ands	r3, r0, #0x7000000	@ extract loc from clidr
- 		mov	r3, r3, lsr #23		@ left align loc bit field
-@@ -1201,6 +1202,7 @@ iflush:
- 		mcr	p15, 0, r10, c7, c10, 4	@ DSB
- 		mcr	p15, 0, r10, c7, c5, 4	@ ISB
- 		mov	pc, lr
-+ENDPROC(__armv7_mmu_cache_flush_fn)
- 
- __armv5tej_mmu_cache_flush:
- 		tst	r4, #1