Re: [PATCH] spi: imx: only do necessary changes to ECSPIx_CONFIGREG

[Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

On Tue, Mar 15, 2016 at 02:24:36PM +0100, Dirk Behme wrote:
> From: Knut Wohlrab <knut.wohlrab-V5te9oGctAVWk0Htik3J/w@public.gmane.org>
> 
> If the SPI chip select (CS) for a dedicated channel is done manually by
> the used higher device driver, the CS may be active while writing to
> ECSPIx_CONFIGREG. To prevent unwanted clock edges when selecting
> the clock mode,  only do the necessary changes to the i.MX SPI
> configuration register and leave not selected channels untouched.
> 
> To prevent unwanted clock edges on first use, an empty dummy
> transmission shall be done by the initialization procedure of the device
> driver of this channel. This will set the clock mode to the correct state.

The patch does the right thing, so:

Acked-by: Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>

Only the above sentence is not clear to me. By device driver you mean
the SPI slave driver (flash, PMIC), right? Isn't this what
bitbang->setup_transfer(spi, NULL), called from spi_bitbang_setup() already
does? spi_bitbang_setup should be called while adding a new SPI slave
device and the setup_transfer with an empty message should setup the
config register correctly without involing the slave device driver.

Sascha


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