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 7:18 PM, Oleksandr Tyshchenko
<olekstysh@xxxxxxxxx> wrote:
> On Thu, Aug 9, 2018 at 7:10 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
>> Hi Oleksandr,
> Hi Julien.
Hi.

>
>>
>>
>> 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.
Sorry for the typo, should be:
R-Car Gen3 is ARM64 (H3 SoC -> r8a7795) 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



-- 
Regards,

Oleksandr Tyshchenko

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