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

Stephen Boyd
2013-05-23T17:54:30Z

On 05/15/13 12:38, Stephen Boyd wrote:
> On 05/08/13 14:47, Stephen Boyd wrote:
>> 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>
>> ---
> Ping?

Russell, shall I add this to the patch tracker?

>
>> 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