[U-Boot] [PATCH 3/13 v4] serial: atmel_usart: Use fixed clock value in SPL version with DM_SERIAL

[Eugen.Hristev at microchip.com]

On 03.04.2019 13:58, Stefan Roese wrote:

> Hi Eugen,
> 
> On 03.04.19 12:52, Eugen.Hristev at microchip.com wrote:
>>
>>
>> On 02.04.2019 14:21, Stefan Roese wrote:
>>
>>> This patch adds an alterative SPL version of atmel_serial_enable_clk().
>>> This enables the usage of this driver without full clock support (in
>>> drivers and DT nodes). This saves some space in the SPL image.
>>>
>>> Please note that this fixed clock support is only added to the SPL code
>>> in the DM_SERIAL part of this file. All boards not using SPL & DM_SERIAL
>>> should not be affected.
>>>
>>> This patch also introduces CONFIG_SPL_UART_CLOCK for the fixed UART
>>> input clock. It defaults to 132096000 for ARCH_AT91 but can be set to
>>> a different value if needed.
>>>
>>> Signed-off-by: Stefan Roese <sr at denx.de>
>>> Cc: Heiko Schocher <hs at denx.de>
>>> Cc: Andreas Bießmann <andreas at biessmann.org>
>>> Cc: Eugen Hristev <eugen.hristev at microchip.com>
>>> ---
>>> v4:
>>> - Restrict SPL_UART_CLOCK on SPL && !SPL_CLK
>>> - Provide default value for non AT91 platforms to not break the
>>>     build
>>> - Fix typo in Kconfig text
>>>
>>> v3:
>>> - Depend fixed clock atmel_serial_enable_clk() function also on
>>>     !CONFIG_SPL_CLK so that board with full clocj support in SPL
>>>     can still use the normal function here
>>> - Introcude CONFIG_SPL_UART_CLOCK and use this Kconfig option instead
>>>     of the hardcoded value
>>>
>>> v2:
>>> - Reword patch subject and commit text to make it more clear, that
>>>     this change only affects ports with SPL and DM_SERIAL enabled
>>>    drivers/serial/Kconfig       | 10 ++++++++++
>>>    drivers/serial/atmel_usart.c | 12 ++++++++++++
>>>    2 files changed, 22 insertions(+)
>>>
>>> diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
>>> index 887cd687c0..79fb397cf9 100644
>>> --- a/drivers/serial/Kconfig
>>> +++ b/drivers/serial/Kconfig
>>> @@ -508,6 +508,16 @@ config ATMEL_USART
>>>          configured in the device tree, and input clock frequency can
>>>          be got from the clk node.
>>> +config SPL_UART_CLOCK
>>> +    int "SPL fixed UART input clock"
>>> +    depends on SPL && !SPL_CLK
>>> +    default 132096000 if ARCH_AT91
>>> +    default 0
>>> +    help
>>> +      Provide a fixed clock value as input to the UART controller. This
>>> +      might be needed on platforms which can't enable CONFIG_SPL_CLK
>>> +      because of SPL image size restrictions.
>>> +
>> Hi Stefan,
>>
>> Looking again over this, the Kconfig you added is useless and has no
>> effect unless ATMEL_USART driver...
>> Can you make it to depend on atmel usart or be named
>> ATMEL_SPL_UART_CLOCK if this is not needed for anything else whatsoever
>> (no other platforms/drivers)
>> This way nobody gets confused that by enabling this Kconfig on their
>> platform, something changes (like a fixed clock for their serial in SPL,
>> which will not happen).
> 
> My first intention was to add this Kconfig option as a generic one,
> which can be used by other (non-AT91) platforms as well. This is
> the reasoning for its name and the non-exclusive availability.
> 
> But I have no hard feelings here. If nobody sees any use of this
> Kconfig option on other platforms (hard for us to guess), then I can
> definitely make your suggested changes from above.
> 

Makes sense, but as it is now, it has no effect on other platforms. So I 
think it's best to make it a generic name indeed, but dependent on 
ATMEL_USART then... and other platforms can add their dependency once 
and if they implement it.

Sounds good to you ?

> Thanks,
> Stefan