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

From: [email-masked] (Dave Martin)
Date: Tue, 25 Jun 2013 15:32:11 +0100

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?

> 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.

Cheers
---Dave