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From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
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Date: Wed, 24 Sep 2014 22:14:07 +0200
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Subject: [PATCH] ARM: BCM5301X: Disable MMU and Dcache during decompression
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Broadcom devices have broken CFE (bootloader) that leaves hardware in an
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invalid state. It causes problems with booting Linux. On Northstar
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devices kernel was randomly hanging in ~25% of tries during early init.
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Hangs used to happen at random places in the start_kernel. On BCM53573
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kernel doesn't even seem to start booting.
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To workaround this problem we need to do following very early:
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1) Clear 2 following bits in the SCTLR register:
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#define CR_M (1 << 0) /* MMU enable */
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#define CR_C (1 << 2) /* Dcache enable */
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2) Flush the whole D-cache
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3) Disable L2 cache
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Unfortunately this patch is not upstreamable as it does above things
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unconditionally. We can't check if we are running on Broadcom platform
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in any safe way and doing such hacks with ARCH_MULTI_V7 is unacceptable
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as it could break other devices support.
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Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
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---
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--- a/arch/arm/boot/compressed/Makefile
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+++ b/arch/arm/boot/compressed/Makefile
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@@ -31,6 +31,11 @@ ifeq ($(CONFIG_ARCH_ACORN),y)
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OBJS += ll_char_wr.o font.o
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endif
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+ifeq ($(CONFIG_ARCH_BCM_5301X),y)
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+OBJS += head-bcm_5301x-mpcore.o
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+OBJS += cache-v7-min.o
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+endif
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+
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ifeq ($(CONFIG_ARCH_SA1100),y)
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OBJS += head-sa1100.o
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endif
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--- /dev/null
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+++ b/arch/arm/boot/compressed/head-bcm_5301x-mpcore.S
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@@ -0,0 +1,37 @@
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+/*
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+ *
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+ * Platform specific tweaks. This is merged into head.S by the linker.
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+ *
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+ */
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+
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+#include <linux/linkage.h>
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+#include <asm/assembler.h>
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+#include <asm/cp15.h>
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+
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+ .section ".start", "ax"
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+
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+/*
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+ * This code section is spliced into the head code by the linker
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+ */
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+
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+__plat_uncompress_start:
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+
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+ @ Preserve r8/r7 i.e. kernel entry values
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+ mov r12, r8
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+
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+ @ Clear MMU enable and Dcache enable bits
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+ mrc p15, 0, r0, c1, c0, 0 @ Read SCTLR
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+ bic r0, #CR_C|CR_M
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+ mcr p15, 0, r0, c1, c0, 0 @ Write SCTLR
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+ nop
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+
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+ @ Call the cache invalidation routine
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+ bl v7_flush_dcache_all
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+ nop
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+ mov r0,#0
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+ ldr r3, =0x19022000 @ L2 cache controller, control reg
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+ str r0, [r3, #0x100] @ Disable L2 cache
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+ nop
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+
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+ @ Restore
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+ mov r8, r12
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--- a/arch/arm/boot/compressed/cache-v7-min.S
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+++ b/arch/arm/boot/compressed/cache-v7-min.S
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@@ -12,6 +12,7 @@
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#include <linux/linkage.h>
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#include <linux/init.h>
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+#include <asm/assembler.h>
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__INIT
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@@ -63,7 +64,7 @@ loop2:
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ARM( orr r11, r11, r9, lsl r2 ) @ factor index number into r11
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THUMB( lsl r6, r9, r2 )
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THUMB( orr r11, r11, r6 ) @ factor index number into r11
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- mcr p15, 0, r11, c7, c14, 2 @ clean & invalidate by set/way
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+ mcr p15, 0, r11, c7, c6, 2 @ clean & invalidate by set/way
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subs r9, r9, #1 @ decrement the index
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bge loop2
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subs r4, r4, #1 @ decrement the way
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