lkml.org 
[lkml]   [2005]   [Dec]   [23]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
DateFri, 23 Dec 2005 10:08:44 +0300
FromVitaly Wool <>
SubjectRe: [PATCH 2.6-git] SPI: add set_clock() to bitbang
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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-12-23 08:14    [from the cache]
©2003-2008