Re: [Xen-devel] [PATCH v1 4/4] xen/arm: Reuse R-Car Gen2 platform code for Stout board

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

On Thu, Aug 9, 2018 at 7:10 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
> Hi Oleksandr,
Hi Julien.

>
>
> On 08/07/2018 08:13 PM, Oleksandr Tyshchenko wrote:
>>
>> On Tue, Aug 7, 2018 at 8:21 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
>>>
>>> On 07/08/18 18:12, Oleksandr Tyshchenko wrote:
>>>>
>>>>
>>>> Hi, Julien
>>>
>>>
>>>
>>> Hi Oleksandr,
>>
>> Hi Julien
>>
>>>
>>>
>>>>
>>>> On Tue, Aug 7, 2018 at 6:18 PM, Julien Grall <julien.grall@xxxxxxx>
>>>> wrote:
>>>>>
>>>>>
>>>>> Hi,
>>>>>
>>>>> On 06/08/18 19:35, Oleksandr Tyshchenko wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>>>>>>
>>>>>> Renesas "Stout" development board (with different expansion boards)
>>>>>> is also based on R-Car Gen2 SoC. So extend compat array with
>>>>>> board's compatible strings.
>>>>>>
>>>>>> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>>>>>> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>>>>>> CC: Julien Grall <julien.grall@xxxxxxx>
>>>>>> ---
>>>>>>     xen/arch/arm/platforms/rcar2.c | 4 ++++
>>>>>>     1 file changed, 4 insertions(+)
>>>>>>
>>>>>> diff --git a/xen/arch/arm/platforms/rcar2.c
>>>>>> b/xen/arch/arm/platforms/rcar2.c
>>>>>> index df0ac84..ee2ded0 100644
>>>>>> --- a/xen/arch/arm/platforms/rcar2.c
>>>>>> +++ b/xen/arch/arm/platforms/rcar2.c
>>>>>> @@ -49,6 +49,10 @@ static int __init rcar2_smp_init(void)
>>>>>>     static const char *const rcar2_dt_compat[] __initconst =
>>>>>>     {
>>>>>>         "renesas,lager",
>>>>>> +    "renesas,r8a7790stout",
>>>>>> +    "renesas,r8a7790stout-view",
>>>>>> +    "renesas,r8a7790stout-had",
>>>>>> +    "renesas,r8a7790stout-full",
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> I am quite reluctant to add compatible that are not present in upstream
>>>>> Linux. Looking at the DT upstreamed in Linux, the compatible for
>>>>> r8a7790
>>>>> SoC
>>>>> seem to be "renesas,r8a7790". Wouldn't it be sufficient to cover all
>>>>> the
>>>>> boards? But ...
>>>>
>>>>
>>>>
>>>> This compatible came from official BSP for this board...
>>>> https://elinux.org/R-Car/Boards/Yocto#Running
>>>>
>>>> I have just checked "renesas,r8a7790" and you was right, it covers
>>>> these modifications. So, I will change.
>>>> Moreover, we can just have only single compatible, which will cover (I
>>>> hope) all boards based on R-Car H2 SoC, including Lager board
>>>> (compatible = "renesas,lager", "renesas,r8a7790")
>>>>
>>>>    static const char *const rcar2_dt_compat[] __initconst =
>>>>    {
>>>> -    "renesas,lager",
>>>> +    "renesas,r8a7790",
>>>>        NULL
>>>>    };
>>>>
>>>> What do you think?
>>>
>>>
>>>
>>> That would be the best.
>>>
>>>>
>>>>>
>>>>> ... don't you have PSCI support on those platforms?
>>>>
>>>>
>>>>
>>>> AFAIK, no.
>>>> This code is definitely needed for Stout board as well, since the SoC
>>>> is the same (R-Car Gen2).
>>>
>>>
>>>
>>> When I looked at the device-tree upstreamed for R-Car Gen2 (I think
>>> r8a7790), PSCI is supported. So I am a bit surprised that the Stout (or
>>> even
>>> lager) does not support it. Are you sure you are not using an old
>>> firmware?
>>
>>
>> This is the topic I am not quite familiar with, so may mistake...
>>
>> Yes, the BSP I use is quite old, but I managed to run it on top of Xen...
>> Just to clarify, saying firmware you mean something running in Secure
>> World, like ARM TF, for example
>> and providing PSCI services? If yes, the BSP for R-Car Gen2 seems
>> doesn't contain it. Only U-Boot is available.
>> But U-Boot was modified to be able to switch A15 cores to HYP mode.
>> Here [1] you can see how it was done for Lager board,
>> something similar I did for Stout board.
>>
>> So, in a nutshell, SMP bring-up under Xen is done in following way:
>> - U-Boot switches all cores to HYP mode and jumps to Xen on a boot
>> core, while non-boot cores are waiting in U-Boot.
>> - Platform SMP init code (rcar2.c) brings each non-boot core to Xen.
>>
>>>
>>> If not, can you please point me to the code in Linux (upstream or BSP)
>>> doing
>>> the SMP bring-up for the R-Car?
>>
>>
>> BSP is based on + additional patches in Yocto layers:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/horms/renesas-backport.git/tree/arch/arm/boot/dts/r8a7790.dtsi?h=bsp/v3.10.31-ltsi/rcar-gen2-1.9.8
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/horms/renesas-backport.git/tree/arch/arm/mach-shmobile/platsmp-apmu.c?h=bsp/v3.10.31-ltsi/rcar-gen2-1.9.8
>>
>> Upstream code:
>>
>> https://github.com/torvalds/linux/blob/master/arch/arm/boot/dts/r8a7790.dtsi
>>
>> https://github.com/torvalds/linux/blob/master/arch/arm/mach-shmobile/platsmp-apmu.c
>>
>> Could you point me a link to device-tree where PSCI is supported?
>
>
> Somehow I thought the platform was 64-bit and found a SOC name very similar
> to it. Sorry for the confusion. PSCI seems indeed not supported for that
> platform.
R-Car Gen3 is ARM64 (H2 SoC -> r8a7790) and does support PSCI.
But R-Car Gen2 is ARM32 (H2 SoC -> r8a7790)

>
> However, the code looks fairly different than what we have in Xen. For
> instance secondary CPU seems to require to initialize CNTVOFF, the function
> to power on a CPU also looks different.
Sorry, which code you are taking about, U-Boot or Linux?

>
> Could you explain why such differences?
>
> Cheers,
>
> --
> Julien Grall



-- 
Regards,

Oleksandr Tyshchenko

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