[U-Boot] [PATCH v4 03/10] Exynos542x: Add workaround for ARM errata 798870

[Akshay Saraswat]

>On 13:27-20150220, Akshay Saraswat wrote:
>> This patch adds workaround for ARM errata 798870 which says
>> "If back-to-back speculative cache line fills (fill A and fill B) are
>> issued from the L1 data cache of a CPU to the L2 cache, the second
>> request (fill B) is then cancelled, and the second request would have
>> detected a hazard against a recent write or eviction (write B) to the
>> same cache line as fill B then the L2 logic might deadlock."
>> 
>> Signed-off-by: Kimoon Kim <kimoon.kim at samsung.com>
>> Signed-off-by: Akshay Saraswat <akshay.s at samsung.com>
>> Reviewed-by: Simon Glass <sjg at chromium.org>
>> Tested-by: Simon Glass <sjg at chromium.org>
>> ---
>> Changes since v3:
>> 	- Added errata number in comment.
>> 	- Moved changes to arm generic armv7.h
>> 
>> Changes since v2:
>> 	- No change.
>> 
>> Changes since v1:
>> 	- Added Reviewed-by & Tested-by.
>> 	- Added space before */ on line # 40.
>> 
>>  arch/arm/include/asm/armv7.h | 16 ++++++++++++++++
>>  1 file changed, 16 insertions(+)
>> 
>> diff --git a/arch/arm/include/asm/armv7.h b/arch/arm/include/asm/armv7.h
>> index a13da23..a2040b7 100644
>> --- a/arch/arm/include/asm/armv7.h
>> +++ b/arch/arm/include/asm/armv7.h
>> @@ -69,6 +69,22 @@
>>  #define CP15DSB	asm volatile ("mcr     p15, 0, %0, c7, c10, 4" : : "r" (0))
>>  #define CP15DMB	asm volatile ("mcr     p15, 0, %0, c7, c10, 5" : : "r" (0))
>>  
>> +/*
>> + * Workaround for ARM errata # 798870
>> + * Set L2ACTLR[7] to reissue any memory transaction in the L2 that has been
>> + * stalled for 1024 cycles to verify that its hazard condition still exists.
>> + */
>> +static inline void v7_enable_l2_hazard_detect(void)
>> +{
>> +	uint32_t val;
>> +
>> +	/* L2ACTLR[7]: Enable hazard detect timeout */
>> +	asm volatile ("mrc     p15, 1, %0, c15, c0, 0\n\t" : "=r"(val));
>> +	val |= (1 << 7);
>> +	asm volatile ("mcr     p15, 1, %0, c15, c0, 0\n\t" : : "r"(val));
>
>This wont work for us in DRA7/OMAP5 L2ACTLR cannot be modified by
>u-boot. has to go to secure world using smc call.
>

If you dont want to execute it, don't call it. As simple as that. :)
If you want to execute it from secure world, then call it from your SMC handler.
Does it make sense?

>> +}
>> +
>> +void v7_en_l2_hazard_detect(void);
>>  void v7_outer_cache_enable(void);
>>  void v7_outer_cache_disable(void);
>>  void v7_outer_cache_flush_all(void);
>
>How about this - using the series:
>https://patchwork.ozlabs.org/patch/443261/                
>https://patchwork.ozlabs.org/patch/443264/                
>https://patchwork.ozlabs.org/patch/443268/                
>https://patchwork.ozlabs.org/patch/443265/                
>https://patchwork.ozlabs.org/patch/443263/                
>https://patchwork.ozlabs.org/patch/443262/                
>https://patchwork.ozlabs.org/patch/443267/                
>https://patchwork.ozlabs.org/patch/443266/                
>https://patchwork.ozlabs.org/patch/443260/                
>-- 
>Regards,
>Nishanth Menon


Regards,
Akshay Saraswat