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

[Marek Vasut]

On 05/26/2016 07:07 PM, Simon Glass wrote:
> 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.

No, whichever I slice it as I plumb in this, I just don't like adding
this complexity only because I might sometimes use UART on this platform
in SPL. I can hack that support in, but in general let's just not do it
afterall to make the driver a little simple(r).

I just added DM/DT support into the JZ4780 and it supports serial too
with minor tweaks to the ns16550 driver and it looks much less
convoluted, so I will just opt for that.


-- 
Best regards,
Marek Vasut