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

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Message-ID: <519E57D2.3050000@codeaurora.org>
Date:	Thu, 23 May 2013 10:54:26 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Russell King <linux@....linux.org.uk>
CC:	Brian Swetland <swetland@...gle.com>, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: avoid mis-detecting some V7 cores in the decompressor

On 05/15/13 12:38, Stephen Boyd wrote:
> On 05/08/13 14:47, Stephen Boyd wrote:
>> From: Brian Swetland <swetland@...gle.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@...gle.com>
>> [sboyd: Clarified and extended commit text]
>> Signed-off-by: Stephen Boyd <sboyd@...eaurora.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
>


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