[U-Boot] [PATCH] mx6: mx6qsabrelite/nitrogen6x: Fix use of gpio number in SF chip select

[Gabbasov, Andrew]

Hi Dirk,
________________________________________
> From: Behme, Dirk - Bosch
> Sent: Thursday, May 30, 2013 14:50
> To: Gabbasov, Andrew
> Cc: u-boot at lists.denx.de
> Subject: Re: [U-Boot] [PATCH] mx6: mx6qsabrelite/nitrogen6x: Fix use of gpio number in SF chip select

[skipped]

> To my understanding, above change is correct, but not complete ;)
> 
> The question is "why has it worked with the wrong setting and nobody
> ever noticed that its wrong?"
> 
> To my understanding the answer is "because the SPI driver does it
> correctly":
> 
> http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=blob;f=drivers/spi/mxc_spi.c;h=5bed858787f610a9c9a46bb2214665a51d60a9e9;hb=refs/heads/master#l376
> 
> So IMHO the gpio_direction_output() above can be removed completely.
> 
> Best regards
> 
> Dirk

Yes, the SPI driver correctly activates and deactivates the CS signal.
But before the first activation it relies on what signal state was set before that.
Setting it early at startup just adds some confidence that we have correct
(inactive) chip select state before the first activation by SPI driver.
Otherwise we have to rely on particular pad configuration (e.g. EIM_D19).
I understand, that we set its configuration to "pull-up" (and this is also
the reset default), and if we do nothing here, it will be recognized as "high".
But in order to make sure, it's more safe to explicitly set the signal to 1.

Thanks.

Best regards,
Andrew