On Thu, Dec 26, 2013 at 09:00 +0200, Baruch Siach wrote: > > I have a few more patches in the queue for adding device tree > support, gpio chip selects, and generic spi queue, but I'm > waiting with time until I get a chance to test them properly.
Just some notes on GPIO backed CS lines. When I recently worked with them (not in mainline, but in a "non-existing" :) tree which is why I haven't upstreamed), I learned the following: With cs-gpios you can have an arbitrary number of CS lines, regardless of how many internal hardwired CS lines the controller may have. Make sure to test setups with high CS numbers as well. Make sure to test with low CS numbers, too, because cs-gpios can both extend the number of internally provided CS lines, as well as "shadow" the internal CS lines. Internal and external lines can get mixed in arbitrary ways. The SPI master driver's code appeared to assume that always in internal CS is involved, without it the transfer of data was stuck. So I had to pick an internal CS trigger in dirty ways despite of using a GPIO line for CS control, just to "unfreeze" the data transmission. You may see a similar issue. To summarize you may want to consider the following DT spec ... cs-gpios = <&pio 0>, <0>, <0>, <0>, <&pio 1>; ... and run your tests with SPI slaves on CS0, CS1, and CS4. virtually yours Gerhard Sittig -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr. 5, D-82194 Groebenzell, Germany Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 Email: [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
