Subject: [PATCH] ARM: keystone: remove hand-coded smc instruction

From: [email-masked] (Santosh Shilimkar)
Date: Tue, 25 Jun 2013 10:40:57 -0400

On Tuesday 25 June 2013 10:32 AM, Dave Martin wrote:
> On Tue, Jun 25, 2013 at 10:27:11AM -0400, Santosh Shilimkar wrote:
>> On Tuesday 25 June 2013 10:13 AM, Dave Martin wrote:
>>> On Fri, Jun 21, 2013 at 06:54:47PM -0400, Santosh Shilimkar wrote:
>>>> On Friday 21 June 2013 05:41 PM, Arnd Bergmann wrote:
>>>>> On Friday 21 June 2013, Santosh Shilimkar wrote:
>>>>>>>
>>>>>> I was curious how you will fix that for a c file.
>>>>>> Just to be clear, I was planning to do that in 3.11-rcx/3.12
>>>>>> time. Let me know if it needs to be done earlier than that.
>>>>>
>>>>> It breaks randconfig builds on arm-soc at the moment, so I'd
>>>>> like the fix as early as possible for 3.11.
>>>>>
>>>> Ok, fix is at end of the email. Let me know if it makes
>>>> to pass both the builds now. I have build and boot tested
>>>> both ARM and THUMB2 builds on Keystone board.
>>>>
>>>> Regards,
>>>> Santosh
>>>>
>>>> From 05d6a5b6cad624fb3791e8c1f8eb7c774f0790d9 Mon Sep 17 00:00:00 2001
>>>> From: Santosh Shilimkar <[email-masked]>
>>>> Date: Fri, 21 Jun 2013 18:35:32 -0400
>>>> Subject: [PATCH] ARM: keystone: Move CPU bringup code to dedicated asm file
>>>>
>>>> Because of inline asm usage in platsmp.c, smc instruction
>>>> creates build failure for ARM V6+V7 build where as using instruction
>>>> encoding for smc breaks the thumb2 build.
>>>>
>>>> So move the code snippet to separate asm file and mark
>>>> it with 'armv7-a$(plus_sec)' to avoid any build issues.
>>>>
>>>> Cc: Arnd Bergmann <[email-masked]>
>>>>
>>>> Signed-off-by: Santosh Shilimkar <[email-masked]>
>>>> ---
>>
>> [..]
>>
>>>> diff --git a/arch/arm/mach-keystone/smc.S b/arch/arm/mach-keystone/smc.S
>>>> new file mode 100644
>>>> index 0000000..9b9e4f7
>>>> --- /dev/null
>>>> +++ b/arch/arm/mach-keystone/smc.S
>>>> @@ -0,0 +1,29 @@
>>>> +/*
>>>> + * Keystone Secure APIs
>>>> + *
>>>> + * Copyright (C) 2013 Texas Instruments, Inc.
>>>> + * 	Santosh Shilimkar <[email-masked]>
>>>> + *
>>>> + * This program is free software,you can redistribute it and/or modify
>>>> + * it under the terms of the GNU General Public License version 2 as
>>>> + * published by the Free Software Foundation.
>>>> + */
>>>> +
>>>> +#include <linux/linkage.h>
>>>> +
>>>> +/**
>>>> + * u32 keystone_cpu_smc(u32 command, u32 cpu, u32 addr)
>>>> + *
>>>> + * Low level CPU monitor API
>>>> + * @command:	Monitor command.
>>>> + * @cpu:	CPU Number
>>>> + * @addr:	Kernel jump address for boot CPU
>>>> + *
>>>> + * Return: Non zero value on failure
>>>> + */
>>>
>>> Oops, looks like I missed the final mail on this thread.  Ignore my
>>> previous mail.
>>>
>>> I still think it would be a good idea to try to consolidate all these
>>> trivial SMC wrappers, but this remains debatable.
>>>
>>>
>>>
>>> Anyway, this looks like it should work, except:
>>>
>>>> +ENTRY(keystone_cpu_smc)
>>>> +	stmfd   sp!, {r4-r12, lr}
>>>> +	smc	#0
>>>> +	dsb
>>>
>>> What's this DSB for?  (You didn't have it in the inline asm version)
>>>
>> Just to drain the write buffer before resuming on non-secure side.
> 
> Why do you need to do that?
> 
To commit any secure side pending writes. I don't remember exactly the
issues but I remember facing issues in power management sequencing with
SMC calls in between. That time a dsb did the trick. In fact I use to
keep 1 before SMC and 1 after. 

>> I actually added it while moving it to asm file.
>>  
>>>> +	ldmfd   sp!, {r4-r12, pc}
>>>> +ENDPROC(keystone_cpu_smc)
>>>
>>> r12 is caller-save btw; you don't need to preserve it.
>>>
>> Indeed. Will update it while adding some more SMC APIs.
>> Its not harmful as such for now.
> 
> If you could change that as soon as you make another modification to
> this file, that would be appreciated.  These code snippets get
> cut and pasted recklessly.
> 
Yep. Thats what I mean.

Regards,
Santosh