Messages in this thread | | | From | David Brownell <> | Subject | Re: [PATCH 2.6-git] SPI: add set_clock() to bitbang | Date | Thu, 22 Dec 2005 16:37:07 -0800 |
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> 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.
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.
So it's like I said earlier. And going to a new message will normally involve a new chipselect, yes ... but maybe not, there's that hint available to avoid the switching.
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