[PATCH] ARM: avoid mis-detecting some V7 cores in the decompressor

Stephen Boyd
2013-05-08T21:48:00Z

From: Brian Swetland <swetland@google.com>

Currently v7 CPUs with an MIDR that has no bits set in the range
[16:12] will be detected as old ARM CPUs with no caches and so
the cache will never be turned on during decompression. ARM's
Cortex chips have an 0xC in the range [16:12] so they never match
this entry, but Qualcomm's Scorpion and Krait processors never
set these bits to anything besides 0 so they always match.

Skip this entry if we've compiled in support for v7 CPUs. This
allows kernel decompression to happen nearly instantly instead of
taking over 20 seconds.

Signed-off-by: Brian Swetland <swetland@google.com>
[sboyd: Clarified and extended commit text]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---
arch/arm/boot/compressed/head.S | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index fe4d9c3..a236190 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -805,6 +805,8 @@ call_cache_fn: adr r12, proc_types
.align 2
.type proc_types,#object
proc_types:
+#if !defined(CONFIG_CPU_V7)
+ /* This collides with some V7 IDs, preventing correct detection */
.word 0x00000000 @ old ARM ID
.word 0x0000f000
mov pc, lr
@@ -813,6 +815,7 @@ proc_types:
THUMB( nop )
mov pc, lr
THUMB( nop )
+#endif

.word 0x41007000 @ ARM7/710
.word 0xfff8fe00
--
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