Re: [Xen-devel] [PATCH v1 3/4] xen/arm: Add SCIFA UART support for early printk

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

On Tue, Aug 7, 2018 at 6:22 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
>
>
> On 07/08/18 15:28, Oleksandr Tyshchenko wrote:
>>
>> On Tue, Aug 7, 2018 at 4:48 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
>>>
>>> Hi,

Hi, Julien

>>
>>
>> Hi, Julien
>>
>>>
>>> On 06/08/18 19:35, Oleksandr Tyshchenko wrote:
>>>>
>>>>
>>>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>>>>
>>>> Add support for Renesas "Stout" development board based on
>>>> R-Car H2 SoC which has SCIFA compatible UART.
>>>>
>>>> Actually existing SCIF UART support (debug-scif.inc) and
>>>> newly added SCIFA UART support (debug-scifa.inc) differ only
>>>> in registers offsets.
>>>
>>>
>>> In that case, could we just extend debug-scif.inc?
>>
>> I was thinking about that, but couldn't find suitable solution without
>> adding extra config option.
>
>
> I had the config option in my mind. But it may not be worth it.
So, if you or anyone else don't mind I leave this patch creating
debug-scifa.inc file.

>
>
>> As I understand, we need to recognize in run-time somehow which
>> interface is present to use proper register offsets,
>> so in UART driver it is easy to recognize using device-tree compatible
>> string, but what to do here in such an early code.
>>
>>>
>>>>
>>>> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>>>> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>>>> CC: Julien Grall <julien.grall@xxxxxxx>
>>>> ---
>>>>    docs/misc/arm/early-printk.txt     |  3 ++-
>>>>    xen/arch/arm/Rules.mk              |  1 +
>>>>    xen/arch/arm/arm32/debug-scifa.inc | 51
>>>> ++++++++++++++++++++++++++++++++++++++
>>>>    3 files changed, 54 insertions(+), 1 deletion(-)
>>>>    create mode 100644 xen/arch/arm/arm32/debug-scifa.inc
>>>>
>>>> diff --git a/docs/misc/arm/early-printk.txt
>>>> b/docs/misc/arm/early-printk.txt
>>>> index f765f59..f1b55d3 100644
>>>> --- a/docs/misc/arm/early-printk.txt
>>>> +++ b/docs/misc/arm/early-printk.txt
>>>> @@ -39,12 +39,13 @@ the name of the machine:
>>>>      - fastmodel: printk on ARM Fastmodel software emulators
>>>>      - hikey960: printk with pl011 with Hikey 960
>>>>      - juno: printk with pl011 on Juno platform
>>>> -  - lager: printk with SCIF0 on Renesas R-Car H2 processors
>>>> +  - lager: printk with SCIF0 on Renesas Lager board (R-Car H2
>>>> processor)
>>>
>>>
>>>
>>> Why this change?
>>
>> This sentence was not entirely correct. Since SCIF0 interface is
>> applicable for Lager
>> board, but is not applicable for Stout board which also based on R-Car
>> H2 processor.
>> Shall I create a separate patch for this small correction?
>
>
> Yes please.
>
>>
>>>
>>>>      - midway: printk with the pl011 on Calxeda Midway processors
>>>>      - mvebu: printk with the MVEBU for Marvell Armada 3700 SoCs
>>>>      - omap5432: printk with UART3 on TI OMAP5432 processors
>>>>      - rcar3: printk with SCIF2 on Renesas R-Car Gen3 processors
>>>>      - seattle: printk with pl011 for AMD Seattle processor
>>>> +  - stout: printk with SCIFA0 on Renesas Stout board (R-Car H2
>>>> processor)
>>>
>>>
>>>
>>> I have started to look at porting that to Kconfig ealyprintk and it is a
>>> massive pain. So I would tend to prefer if we avoid adding more
>>> convenience
>>> alias and instead document on the wiki page how to use earlyprintk for
>>> that.
>>
>> I will update a wiki page. Shall I drop this string in early-printk.txt?
>
>
> Yes please.
>
> Cheers,
>
> --
> Julien Grall



-- 
Regards,

Oleksandr Tyshchenko

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