>-------- Оригинално писмо --------
>От: Dave Martin
>Относно: Re: [PATCH v2 1/2] ARM: OMAP: Add secure function omap_smc3() which
calling instruction smc #1
>До: Pali Rohár
>Изпратено на: Сряда, 2013, Юли 10 20:45:26 EEST
>
>
>On Wed, Jul 10, 2013 at 02:59:04PM +0200, Pali Rohár wrote:
>> Other secure functions omap_smc1() and omap_smc2() calling instruction smc #0
>> but Nokia RX-51 board needs to call smc #1 for PPA access.
>>
>> Signed-off-by: Ivaylo Dimitrov
>> Signed-off-by: Pali Rohár
>> ---
>> arch/arm/mach-omap2/omap-secure.h | 1 +
>> arch/arm/mach-omap2/omap-smc.S | 22 +++++++++++++++++++++-
>> 2 files changed, 22 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mach-omap2/omap-secure.h b/arch/arm/mach-omap2/omap-secure.h
>> index 0e72917..c4586f4 100644
>> --- a/arch/arm/mach-omap2/omap-secure.h
>> +++ b/arch/arm/mach-omap2/omap-secure.h
>> @@ -51,6 +51,7 @@
>> extern u32 omap_secure_dispatcher(u32 idx, u32 flag, u32 nargs,
>> u32 arg1, u32 arg2, u32 arg3, u32 arg4);
>> extern u32 omap_smc2(u32 id, u32 falg, u32 pargs);
>> +extern u32 omap_smc3(u32 id, u32 process, u32 flag, u32 pargs);
>> extern phys_addr_t omap_secure_ram_mempool_base(void);
>> extern int omap_secure_ram_reserve_memblock(void);
>>
>> diff --git a/arch/arm/mach-omap2/omap-smc.S b/arch/arm/mach-omap2/omap-smc.S
>> index f6441c1..5c02b8d 100644
>> --- a/arch/arm/mach-omap2/omap-smc.S
>> +++ b/arch/arm/mach-omap2/omap-smc.S
>> @@ -1,9 +1,11 @@
>> /*
>> - * OMAP44xx secure APIs file.
>> + * OMAP34xx and OMAP44xx secure APIs file.
>> *
>> * Copyright (C) 2010 Texas Instruments, Inc.
>> * Written by Santosh Shilimkar
>> *
>> + * Copyright (C) 2012 Ivaylo Dimitrov
>> + * Copyright (C) 2013 Pali Rohár
>> *
>> * 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
>> @@ -54,6 +56,24 @@ ENTRY(omap_smc2)
>> ldmfd sp!, {r4-r12, pc}
>> ENDPROC(omap_smc2)
>>
>> +/**
>> + * u32 omap_smc3(u32 service_id, u32 process_id, u32 flag, u32 pargs)
>> + * Low level common routine for secure HAL and PPA APIs via smc #1
>> + * r0 - @service_id: Secure Service ID
>> + * r1 - @process_id: Process ID
>> + * r2 - @flag: Flag to indicate the criticality of operation
>> + * r3 - @pargs: Physical address of parameter list
>> + */
>> +ENTRY(omap_smc3)
>> + stmfd sp!, {r4-r12, lr}
>
>You don't need to save/restore r12. The ABI allows it to be clobbered
>across function calls.
>
>> + mov r12, r0 @ Copy the secure service ID
>> + mov r6, #0xff @ Indicate new Task call
>> + dsb
>> + dmb
>
>dsb synchronises a superset of what dmb synchronises, so the dmb here is
>not useful.
>
>In any case, any code calling this must flush the region addressed by
>r3 beforehand anyway, which will include a dsb as part of its semantics
>-- this is how you call it from rx51_secure_dispatcher().
>
>So I think the dsb may not be needed here (?)
>
>Cheers
>---Dave
>
>
Could be, but I wonder why almost all the kernel code(I am aware of) that uses SMC and is written by TI, is storing r12 and is using both DSB and DMB. See arch/arm/mach-omap2/sleep34xx.S or arch/arm/mach-omap2/omap-smc.S for examples. I'd rather play it safe and leave it that way, unless someone confirms the other code using SMC has extra DSB/DMB instructions too. I wouldn't risk passing invalid/stale data to the Secure Monitor to just save 8 bytes and barriers in a performance non-critical code which will be called only a couple of times during the boot-up process. r12 save/restore is a legacy from omap_smc2 in omap-smc.S, so I guess it can go away without much of a trouble.
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