[PATCH V2 01/12] spi/mxs: Always set LOCK_CS
Marek Vasut
marex at denx.de
Sun Apr 14 14:01:52 EDT 2013
Hello Trent,
> There are two bits which control the CS line in the CTRL0 register:
> LOCK_CS and IGNORE_CRC. The latter would be better named DEASSERT_CS
> in SPI mode.
>
> LOCK_CS keeps CS asserted though the entire transfer. This should
> always be set. The DMA code will always set it, explicitly on the
> first segment of the first transfer, and then implicitly on all the
> rest by never clearing the bit from the value read from the ctrl0
> register.
>
> The only reason to not set LOCK_CS would be to attempt an altered
> protocol where CS pulses between each word. Though don't get your
> hopes up if you want to do this, as the hardware doesn't appear to do
> this in any sane manner.
>
> The code can be simplified by just setting LOCK_CS once and then not
> needing to deal with it in the PIO and DMA transfer functions.
>
> Signed-off-by: Trent Piepho <tpiepho at gmail.com>
> Cc: Marek Vasut <marex at denx.de>
> Cc: Fabio Estevam <fabio.estevam at freescale.com>
> Cc: Shawn Guo <shawn.guo at linaro.org>
Will we see a V3 of this stuff? I don't want to see this lost.
Best regards,
Marek Vasut
More information about the linux-arm-kernel
mailing list