[U-Boot] [PATCH 03/13 v3] serial: atmel_usart: Use fixed clock value in SPL version with DM_SERIAL

[Stefan Roese]

Hi Eugen,

On 02.04.19 12:12, Eugen.Hristev at microchip.com wrote:
> 
> 
> On 02.04.2019 11:57, 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>
>> Reviewed-by: Heiko Schocher <hs at denx.de>
>> Tested on the taurus board:
>> Tested-by: Heiko Schocher <hs at denx.de>
>> ---
>> 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       |  9 +++++++++
>>    drivers/serial/atmel_usart.c | 12 ++++++++++++
>>    2 files changed, 21 insertions(+)
>>
>> diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
>> index 887cd687c0..d6bf8309d3 100644
>> --- a/drivers/serial/Kconfig
>> +++ b/drivers/serial/Kconfig
>> @@ -508,6 +508,15 @@ 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
>> +	default 132096000 if ARCH_AT91
> 
> Hi Stefan,
> 
> This doesn't look good. This has to be unset for the platforms that do
> not specifically set it.
> 
> For example, when I build the sama5d2_xplained_mmc_defconfig, I look in
> .config and :
> 
> CONFIG_SPL_UART_CLOCK=132096000
> 
> This may be unused, but it's confusing

Okay, I agree.
  
> Can you make this default unset and then specifically set it in the
> boards that need it ? ( the specific defconfig )
> 
> And if you have a mutual exclusion with CONFIG_SPL_CLK can we make it
> somehow ? (in a menu or choice..., either old behavior or fixed uart clock)

How about this version?

config SPL_UART_CLOCK
	int "SPL fixed UART input clock"
	depends on SPL && !SPL_CLK
	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 restirctions.

Thanks,
Stefan