On Mon, Jul 23, 2007 at 10:33:31AM -0700, David Brownell wrote: > On Monday 23 July 2007, Anton Vorontsov wrote: > > On Thu, Jul 19, 2007 at 01:28:17PM -0700, David Brownell wrote: > > > > I notice that driver disregards the cs_change instructions in the > > > messages ... I could imagine how that could make a big difference. > > For example, the extra flapping on the chipselect changes timings... > > > > > If that hardware were doing the right thing, then it would work > > > reliably! Since it's not reliable, it's doing something wrong. > > > You seem to think it's not a hardware issue; that may be true. > > > > > > Recall that the first dozen or so commands worked just fine. The > > > issue was that some byte that should have been all-ones or 0xfe > > > reported instead an 0xf8. That's not the kind of error that can > > > be explained by clock skew; it covers at least two bits. > > > > Yup, I've either noticed that 0xf8 and 0xfe differs by only two > > bits (and by three if comparing to 0xff). But I can't really > > explain it yet. > > See if fixing the cs_change handling -- so that chipselect never > goes inactive except between MMC requests -- helps.
Okay.. I've looked into cs_change for spi_mpc83xx, and it seems bitbang framework (which is used by spi_mpc83xx driver) handle cs_change by itself. At least bitbang_work() doing very similar things done by other drivers not using bitbang library. > Minimally, > you'll notice that mode 0 adds extra delays (albeit only 1/2 clock) > before the clock starts toggling; and that deslecting cards > except between requests or while the card issues BUSY, falls into > the "undefined behavior" category. So while that might not be > able to trigger certain perversions, dropping a few clocks in > some odd cases would not seem to violate the spec... > > - Dave Thanks, -- Anton Vorontsov email: [EMAIL PROTECTED] backup email: [EMAIL PROTECTED] irc://irc.freenode.net/bd2 ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ spi-devel-general mailing list spi-devel-general@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/spi-devel-general
