[U-Boot] [PATCH] arm: re-implement proper ISB instruction for ARMv7-A

[Ziyuan Xu]

Hi,

On 2016年07月28日 19:03, Chen-Yu Tsai wrote:
> Hi,
>
> On Thu, Jul 28, 2016 at 6:13 PM, Ziyuan Xu <xzy.xu at rock-chips.com> wrote:
>> For ARMv7-A architecture, the valid ISB instruction is asm volatile("isb").
>>
>> This patch fixes the U-Boot was stuck in invalidate_dcache_all() before
>> booting linux kernel, which occurred on rk3288-base development board
>> such as evb-rk3288, rock2-rk3288. And something output via console like:
>>
>> => bootz 0x2000000
>> 0x02000000
>>     ramdisk start = 0x00000000, ramdisk end = 0x00000000
>>     Continuing to boot without FDT
>>     Initial value for argc=3
>>     Final value for argc=3
>>     using: ATAGS
>>
>>     Starting kernel ...
>>
>> Linux kernel exactly the same way(see arch/arm/include/asm/barrier.h).
>>
>> Signed-off-by: Ziyuan Xu <xzy.xu at rock-chips.com>
>> ---
>>
>>   arch/arm/include/asm/system.h | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
>> index 2bdc0be..12d4ba0 100644
>> --- a/arch/arm/include/asm/system.h
>> +++ b/arch/arm/include/asm/system.h
>> @@ -227,13 +227,15 @@ void __noreturn psci_system_reset(bool smc);
>>    */
>>   void save_boot_params_ret(void);
>>
>> -#define isb() __asm__ __volatile__ ("" : : : "memory")
>> -
>>   #define nop() __asm__ __volatile__("mov\tr0,r0\t@ nop\n\t");
>>
>>   #ifdef __ARM_ARCH_7A__
>> +#define isb() __asm__ __volatile__ ("isb" : : : "memory")
>> +
>>   #define wfi() __asm__ __volatile__ ("wfi" : : : "memory")
>>   #else
>> +#define isb() __asm__ __volatile__ ("" : : : "memory")
>> +
>>   #define wfi()
>>   #endif
>>
> arch/arm/include/asm/barriers.h already has a proper set of
> ISB/DSB macros. Please consider using those instead.
I know just what you mean.
arch/arm/include/asm/barriers.h defined ISB macro.  If I only want to 
fix the issue which I hit on rk3288 board, I just use ISB in 
arch/arm/include/asm/system.h::set_cr() instead of isb(). But isb() had 
been invoked in some places, IMHO, this patch is more apposite.:-)
>
> You'll see they also support ARMv6's CP15 ISB/DSB.
>
> Regards
> ChenYu
>
>
>