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

[Stefan Roese]

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.

Thanks,
Stefan