[linux-dvb] Re: Busy waiting in i2c_busy_rise_and_fall (was: Re: Re: full featured card without signal and required video memory investigation)

[Oliver Endriss <o.endriss@gmx.de>]

On Tuesday 15 July 2003 16:23, Matthew Davis wrote:
> On Tuesday 15 July 2003 06:23 am, Oliver Endriss wrote:
> > Hm, I tested this and could *not* verify this problem:
> > Reading IICSTA always returns a valid value (busy flag set).
> > Really strange. Anyway, to be on the safe side, a dummy read
> > should be added.
>
> Sorry to jump in so late on this discussion.  I played with the I2C
> bus awhile back, and found that with the system I was working on it
> *was* a timing problem.  Two reads just gave the I2C bus enough time
> to settle.
>
> This combination worked every time: udelay(2) and then loop until
> (status shows not busy && the upload bits for MC2 == 0).  Maybe I'm
> way off and missed something reading the spec, but this has worked
> without any problems for a while... though I have not tested to see
> at what speed I can load data with this.

Well, the way it is done now should always work. We do one dummy read 
and wait 20us, before valid data in IICSTA is expected.

Oliver


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