On 2016-11-11 13:18, Peter Rosin wrote: > On 2016-11-11 13:04, Peter Rosin wrote: >> On 2016-11-11 12:47, MikeB wrote: >>> On Thu, Nov 10, 2016 at 8:01 AM, Peter Rosin <peda@xxxxxxxxxx> wrote: >>>>> There is however one requirement, the CPLD-mux must be "mux-locked" >>>>> as explained in Documentation/i2c/i2c-topology. Otherwise accesses >>>>> to devices behind that mux will lock the PCA9547 mux for the full >>>>> duration of the transaction and thus lock out any attempts to update >>>>> the CPLD mux as part of the transaction. >>> >>> Thank you for the informative reply. I was unfamiliar with the new >>> mux and parent locking schemes. They do make the solution for this >>> problem much easier to deal with. I'm working with release 4.4 >>> (Ubuntu Xenial), so the mux/parent locking hadn't shown up on my radar >>> yet. Unfortunately, the target release for my work is and will remain >>> 4.4 for a while. >> >> Lucky you :-) >> >> Anyway, you might be able to backport the changes? >> >> Start with: >> >> a7ab72390b77062420fb50e4451f71c9321aae05 >> "i2c: mux: add common data for every i2c-mux instance" >> >> through to >> >> 23fe440c59b9f08afe108e7ec7b6714cb2a3b955 >> "i2c: mux: drop old unused i2c-mux api" >> >> And then: >> >> 785d32c7a9638a96730686663564d1842f7c2f03 >> "i2c: allow adapter drivers to override the adapter locking" >> >> through to >> >> f76b724ee915415c52068c622ca48c652c1bd10c >> "i2c-mux: document i2c muxes and elaborate on parent-/mux-locked muxes" > > Correction, those two commits became > 8320f495cf441d593f7cd4f30e6b63455be71a2c and > 2254d24aff3ab472dca287aef0123e8f0e06a14a when they got upstream. > >> There are a handful of commits right after that that are also >> related, but they should be irrelevant to you... >> >> Haven't tried it though, YMMV, and I might have forgotten a patch >> or two that came in later, but I don't remember any serious fallout... For the archives, this is a bugfix for one of the commits mentioned: ad092de60f865c1ad94221bd06d381ecea446cc8 "i2c: i2c-mux-pca954x: fix deselect enabling for device-tree" Cheers, Peter -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
