[U-Boot] [PATCH v1 08/16] arm: socfpga: stratix10: Add mailbox support for Stratix10 SoC

[Marek Vasut]

On 05/11/2018 11:25 AM, Ley Foon Tan wrote:
> On Fri, May 11, 2018 at 4:44 PM, Marek Vasut <marex at denx.de> wrote:
>> On 05/11/2018 07:45 AM, Ley Foon Tan wrote:
>>> On Thu, May 10, 2018 at 6:09 PM, Marek Vasut <marex at denx.de> wrote:
>>>> On 05/10/2018 10:45 AM, Ley Foon Tan wrote:
>>>>> On Tue, May 8, 2018 at 5:21 PM, Marek Vasut <marex at denx.de> wrote:
>>>>>> On 05/08/2018 08:49 AM, Ley Foon Tan wrote:
>>>>>>> On Thu, Apr 19, 2018 at 10:53 AM, Marek Vasut <marex at denx.de> wrote:
>>>>>>>> On 04/19/2018 11:50 AM, Ley Foon Tan wrote:
>>>>>>>>> Add mailbox support for Stratix SoC
>>>>>>>>>
>>>>>>>>> Signed-off-by: Ley Foon Tan <ley.foon.tan at intel.com>
>>>>>>>>> Signed-off-by: Chin Liang See <chin.liang.see at intel.com>
>>>>>>>>> ---
>>>>>>
>>>>>> [...]
>>>>>>
>>>>>>>>> +static __always_inline int mbox_polling_resp(u32 rout)
>>>>>>>>> +{
>>>>>>>>> +     static const struct socfpga_mailbox *mbox_base =
>>>>>>>>> +                                     (void *)SOCFPGA_MAILBOX_ADDRESS;
>>>>>>>>> +     u32 rin;
>>>>>>>>> +     unsigned long i = ~0;
>>>>>>>>> +
>>>>>>>>> +     while (i) {
>>>>>>>>> +             rin = readl(&mbox_base->rin);
>>>>>>>>> +             if (rout != rin)
>>>>>>>>> +                     return 0;
>>>>>>>>
>>>>>>>> This looks like include/wait_bit.h reimplementation
>>>>>>> The reason we use this method instead of using wait_bit because this
>>>>>>> function will use in Secure Monitor Call (SMC) call as well.
>>>>>>> When run in secure section, timer is not available.  So, we can't use
>>>>>>> wait_for_bit.
>>>>>>
>>>>>> Can't you just do timer_init() then ?
>>>>> We can't use timer in secure region. This SMC code is resident in
>>>>> onchip memory (secure region) while Linux is running.
>>>>> So, timer might be used by Linux.
>>>>
>>>> So pieces of U-Boot remain in memory and get called by Linux, right ?
>>> Normal U-boot (in DDR) is destroyed after Linux is running, only SMC
>>> code Onchip memory will remain.
>>> The existing U-boot have support this SMC feature, platform just need
>>> to configure the CONFIG_ARMV8_SECURE_BASE for the secure section.
>>> Of course, we need to enable CONFIG_ARMV8_PSCI too.
>>
>> So piece of U-Boot then becomes the part which handles PSCI calls from
>> Linux, do I understand it correctly ?
> Yes, and we put this piece of code in onchip memory in our platform so
> it doesn't corrupted by Linux.
> 
> You can see detail in
> http://git.denx.de/?p=u-boot.git;a=blob;f=arch/arm/cpu/armv8/u-boot.lds
> All code related to PSCI/SMC will put in secure section.

I see, nice, I didnt know about that. Thanks

-- 
Best regards,
Marek Vasut