On Tue, Oct 3, 2017 at 7:09 PM, Doug Berger <open...@gmail.com> wrote: > On 10/03/2017 06:55 PM, Gregory Fong wrote: >> Hi Doug, >> >> On Fri, Sep 29, 2017 at 8:40 PM, Doug Berger <open...@gmail.com> wrote: >>> The basic memory-mapped GPIO controller lock must be released >>> before calling the registered GPIO interrupt handlers to allow >>> the interrupt handlers to access the hardware. Otherwise, the >>> hardware accesses will deadlock when they attempt to grab the >>> lock. >> >> I was having some trouble understanding exactly what the problem was >> here, but I think I see it now. Since this locks the entire bank, >> where some GPIOs might be set as inputs and some as inputs (and >> interrupt sources), then an interrupt on a GPIO that is supposed to >> set another GPIO in the bank would result in deadlock. Is that >> correct? If so, please update the commit message to make that clear, >> and nice fix. If not that, it would be nice to know what scenario can >> cause a problem. > > That is an example, but there are really many possibilities. > > Basically, if a registered interrupt handler wants to access its GPIO > you are likely to run into trouble. Another example might be an > interrupt that is configured to trigger on either edge transition and > the handler wants to know whether the input is currently high or low. > > I can submit a V2 with a change in the description if you would like, > but I'm not sure what the clearest example would be.
If you could just mention both of these possible cases, that would be great! With that change, Acked-by: Gregory Fong <gregory.0...@gmail.com>
