[U-Boot] [PATCH] serial: 16550: Add JZ47xx support

[Simon Glass]

Hi Marek,

On 26 May 2016 at 10:53, Marek Vasut <marex at denx.de> wrote:
> On 05/26/2016 06:48 PM, Simon Glass wrote:
>> Hi Marek,
>>
>> On 26 May 2016 at 10:47, Marek Vasut <marex at denx.de> wrote:
>>> On 05/26/2016 06:44 PM, Simon Glass wrote:
>>>> Hi Marek,
>>>>
>>>> On 26 May 2016 at 10:34, Marek Vasut <marex at denx.de> wrote:
>>>>> On 05/26/2016 03:29 PM, Simon Glass wrote:
>>>>>> Hi Marek,
>>>>>>
>>>>>> On 25 May 2016 at 16:35, Marek Vasut <marex at denx.de> wrote:
>>>>>>> On 05/26/2016 12:31 AM, Daniel Schwierzeck wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> Am 26.05.2016 um 00:21 schrieb Marek Vasut:
>>>>>>>>> On 05/26/2016 12:17 AM, Daniel Schwierzeck wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Am 25.05.2016 um 02:19 schrieb Marek Vasut:
>>>>>>>>>>> The Ingenic JZ47xx requires special bit (UART_EN) set in FCR register
>>>>>>>>>>> in order to work at all. Add this special case handling into the driver.
>>>>>>>>>>>
>>>>>>>>>>> Signed-off-by: Marek Vasut <marex at denx.de>
>>>>>>>>>>> Cc: Tom Rini <trini at konsulko.com>
>>>>>>>>>>> Cc: Simon Glass <sjg at chromium.org>
>>>>>>>>>>> Cc: Daniel Schwierzeck <daniel.schwierzeck at gmail.com>
>>>>>>>>>>> Cc: Paul Burton <paul.burton at imgtec.com>
>>>>>>>>>>> ---
>>>>>>>>>>>  drivers/serial/ns16550.c | 8 ++++++++
>>>>>>>>>>>  1 file changed, 8 insertions(+)
>>>>>>>>>>>
>>>>>>>>>>> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
>>>>>>>>>>> index 30ba0aa..1323881 100644
>>>>>>>>>>> --- a/drivers/serial/ns16550.c
>>>>>>>>>>> +++ b/drivers/serial/ns16550.c
>>>>>>>>>>> @@ -50,6 +50,14 @@ DECLARE_GLOBAL_DATA_PTR;
>>>>>>>>>>>  #endif
>>>>>>>>>>>  #endif
>>>>>>>>>>>
>>>>>>>>>>> +#ifdef CONFIG_ARCH_JZ47XX
>>>>>>>>>>> +#undef UART_FCRVAL
>>>>>>>>>>> +/* Ingenic JZ47xx SoCs require that a 'UART Module Enable' bit be set */
>>>>>>>>>>> +#define UART_FCR_UME              0x10
>>>>>>>>>>> +#define UART_FCRVAL (UART_FCR_FIFO_EN | UART_FCR_RXSR |   \
>>>>>>>>>>> +               UART_FCR_TXSR | UART_FCR_UME)
>>>>>>>>>>> +#endif
>>>>>>>>>>
>>>>>>>>>> I think this could be added as DT property
>>>>>>>>>
>>>>>>>>> Not for SPL, which has 14 kiB size limit and it is itching to overflow.
>>>>>>>>> I am literally counting bytes in the SPL and removing slop from
>>>>>>>>> structures to make it fit, just barely. With the USB loader, I can
>>>>>>>>> brutalize the SPL into having extremely rudimentary UART support now
>>>>>>>>> (like printch() being the most advanced output mechanism, but you can
>>>>>>>>> only use it three times, otherwise the code won't fit and the board is
>>>>>>>>> eaten by demons) and this is where this patch comes into play.
>>>>>>>>>
>>>>>>>>> So yes, for full u-boot, this _should_ be part of DT. For SPL, please apply.
>>>>>>>>>
>>>>>>>>
>>>>>>>> ok, but wouldn't it be better to introduce an option like
>>>>>>>> CONFIG_SYS_NS16550_UME instead of using the SoC-specific
>>>>>>>> CONFIG_ARCH_JZ47XX. This driver is messed up enough ;)
>>>>>>>
>>>>>>> I was undecided between this (like the IER) and adding new ifdef (like
>>>>>>> SOC_KEYSTONE). Whichever way is fine with me. Yeah, the driver is
>>>>>>> repugnant for sure.
>>>>>>>
>>>>>>>>>>> +
>>>>>>>>>>>  #ifndef CONFIG_SYS_NS16550_IER
>>>>>>>>>>>  #define CONFIG_SYS_NS16550_IER  0x00
>>>>>>>>>>>  #endif /* CONFIG_SYS_NS16550_IER */
>>>>>>>>>>>
>>>>>>
>>>>>> That way seems better to me. You should be able to add your UME flag
>>>>>> as a Kconfig for this driver, in drivers/serial/Kconfig, which
>>>>>> defaults to 0. It would be good to keep out board-specific stuff from
>>>>>> this file, as you did with OMAP1510.
>>>>>
>>>>> I'm not really sure I want to expose the CONFIG_SYS_NS16550_FCR override
>>>>> via Kconfig. The extra bits should be set via DT props
>>>>> unless there is some really good reason why that cannot be done
>>>>> (like size limitation in SPL or DT not available).
>>>>>
>>>>> I tried these approaches:
>>>>> 1) Add Kconfig option for CONFIG_SYS_NS16550_FCR , where you
>>>>>    set specific byte value. This makes it hard to figure out
>>>>>    which bits are set in the FCR just by looking at the value.
>>>>> 2) Add Kconfig option selected if ARCH_JZ47XX is selected and
>>>>>    use that in the driver to add the extra UME bit.
>>>>> 3) Define CONFIG_SYS_NS16550_FCR in include/configs/board.h
>>>>>    using the macros from ns16550.h . This makes it obvious
>>>>>    which bits are set.
>>>>>
>>>>> I am undecided between 2 and 3, but inclined to go with 3.
>>>>> What do you think ?
>>>>
>>>> How about making your feature an option, like CONFIG_SYS_NS16550_UEN,
>>>> which defaults to 0, but in your case is 0x10. You can OR it into the
>>>> value.
>>>
>>> That's quite close to 1) , but then what if someone comes and wants to
>>> remove some bits from the FCR instead of adding some?
>>
>> Seems like speculative complexity to me - let's worry about it when it happens!
>
> Heh, ok. But if we add Kconfig stuff, we can as well go with option 2) ,
> which would only show up if JZ47XX is selected. Since this bits is
> specific to this lineup of SoCs , that makes sense in my head. What do
> you think ?

SGTM.

- Simon