Re: [PATCH 2.6-git] SPI: add set_clock() to bitbang

[Vitaly Wool]

David Brownell wrote:

> > No, suppose there're two devices behind the same SPI bus that have 
> > different clock constraints. As active SPI device change may well happen 
> > when each new message is processed, we'll need to set up clocks again 
> > for each message. Right?
> >    
>
> Clock is coupled to chipselect/device.  When the bus controller
> switches to the other device, it updates the clock accordingly.
>  
Yeah, but chipselect is called on per-transfer basis what is likely to 
be redundant for clock setting.
Per-message clock configuration is enough AFAIS.

> How exactly that's done is system-specific.  Many controllers
> just have a register per chipselect, listing stuff like SPI mode,
> clock divisor, and word size.  So switching to that chipselect
> kicks those in automatically ... devices ignore the clock unless
> they've been selected.
>  
Hmm, usually clocks are configured for the bus not device.
So, summarizing, you haven't convinced me yet. :)

Vitaly
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