On 17/02/15 16:06, Robert Abel wrote: > Hi Roger, > > On Tue, Feb 17, 2015 at 2:52 PM, Roger Quadros <rogerq@xxxxxx> wrote: >> nobody stops the DT binding from specifying a large enough "gpmc,wait-monitoring-ns" value. >> The driver must use that to scale the GPMC_CLK if it doesn't fit in the GPMC_FCLK. >> This feature can come separately though. So for now I was suggesting to set the divisor to 1. >> [...] >> AFAIK "gpmc,sync-clk-ps" is not specified for asynchronous devices so it defaults to 0 >> in the driver. > > As you have rightly pointed out, sync-clk-ps defaults to 0, i.e. > divider 1. My solution would work for people /now/ with different > gpmc,wait-monitoring-ns requirements. Of course, in general you're > right, the driver could compute that on its own. However, this > influences sampling behavior of the GPMC, which is somewhat strange > anyway. Since I lack a proper test setup and time to experiment with > the GPMC, I'd compromise on leaving sync-clk-ps default to 0, divider > defaults to 1. If somebody feels up to implementing driver-side > GPMC_CLK scaling, they might as well nix the dependency at that point > in time. Right now, keeping the dependency seems more useful to users > than killing it right away. one more thing to note is that just specifying sync-clk-ps in DT is not enough for asynchronous devices. The driver doesn't set gpmc_t->sync_clk if "gpmc,sync-read" or "gpmc,sync-write" was not set in the DT, which would be the case for asynchronous devices. > >> What I'm stressing on is that there shouldn't be any dependency on "gpmc,sync-clk-ps" for >> asynchronous devices. It also becomes easier to specify the wait-monitoring-ns as we don't need >> to cross reference with "sync-clk-ps". > > As an aside: There shouldn't be a dependency on the FCLK for > synchronous accesses either. The GPMC driver is in a somewhat terrible > state that synchronous protocols have to specify in ns, which get > scaled by the startup FCLK period... So this wrongful dependency > doesn't make my top ten, especially since it right now would fit a use > case. What is your proposal to make things better? And what is your use case that doesn't work with existing setup? cheers, -roger -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
