From e1e2f6e4c5759aab3a8cfb1a0c19017ea770dfd2 Mon Sep 17 00:00:00 2001 From: Florian Fainelli Date: Fri, 9 Jan 2015 19:34:43 +0100 Subject: [PATCH] ARM: 8276/1: Make CPU_DCACHE_DISABLE depend on !SMP Enabling CPU_DCACHE_DISABLE on a SMP capable system will prevent the kernel from booting because of the following ldrex instruction in arch_spin_lock: (gdb) x/10i $pc => 0xc053cfa8 <_raw_spin_lock+4>: ldrex r3, [r0] 0xc053cfac <_raw_spin_lock+8>: add r2, r3, #65536 ; 0x10000 which is taken by the very first printk call: at /home/fainelli/work/linux/arch/arm/include/asm/spinlock.h:65 fmt=0xc0637650 " 01 66Booting Linux on physical CPU 0x%xn", args=) at kernel/printk/printk.c:1525 fmt=0xc05370f4 " 24320215342 04340235344 20320215342 36377/341 17") at kernel/printk/printk.c:1688 ldrex requires exclusive monitor(s) (local or global) which are no longer working when the Data cache is disabled in CP15 and will just hang the CPU there. Acked-by: Arnd Bergmann Signed-off-by: Florian Fainelli Signed-off-by: Russell King --- arch/arm/mm/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index 9b4f29e595a4..133ecff6664e 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -738,7 +738,7 @@ config CPU_ICACHE_DISABLE config CPU_DCACHE_DISABLE bool "Disable D-Cache (C-bit)" - depends on CPU_CP15 + depends on CPU_CP15 && !SMP help Say Y here to disable the processor data cache. Unless you have a reason not to or are unsure, say N.