On 09/08/2015 02:30 AM, Tomeu Vizoso wrote: > On 7 September 2015 at 22:50, Rob Herring <robherring2@xxxxxxxxx> wrote: >> On Mon, Sep 7, 2015 at 7:23 AM, Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx> wrote: >>> Hello, >>> >>> I have a problem with the panel on my Tegra Chromebook taking longer >>> than expected to be ready during boot (Stéphane Marchesin reported what >>> is basically the same issue in [0]), and have looked into ordered >>> probing as a better way of solving this than moving nodes around in the >>> DT or playing with initcall levels and linking order. >>> >>> While reading the thread [1] that Alexander Holler started with his >>> series to make probing order deterministic, it occurred to me that it >>> should be possible to achieve the same by probing devices as they are >>> referenced by other devices. >>> >>> This basically reuses the information that is already implicit in the >>> probe() implementations, saving us from refactoring existing drivers or >>> adding information to DTBs. >>> >>> During review of v1 of this series Linus Walleij suggested that it >>> should be the device driver core to make sure that dependencies are >>> ready before probing a device. I gave this idea a try [2] but Mark Brown >>> pointed out to the logic duplication between the resource acquisition >>> and dependency discovery code paths (though I think it's fairly minor). >>> >>> To address that code duplication I experimented with Arnd's devm_probe >>> [3] concept of having drivers declare their dependencies instead of >>> acquiring them during probe, and while it worked [4], I don't think we >>> end up winning anything when compared to just probing devices on-demand >>> from resource getters. >>> >>> One remaining objection is to the "sprinkling" of calls to >>> of_device_probe() in the resource getters of each subsystem, but I think >>> it's the right thing to do given that the storage of resources is >>> currently subsystem-specific. >>> >>> We could avoid the above by moving resource storage into the core, but I >>> don't think there's a compelling case for that. >>> >>> I have tested this on boards with Tegra, iMX.6, Exynos, Rockchip and >>> OMAP SoCs, and these patches were enough to eliminate all the deferred >>> probes (except one in PandaBoard because omap_dma_system doesn't have a >>> firmware node as of yet). >>> >>> Have submitted a branch [5] with only these patches on top of thursday's >>> linux-next to kernelci.org and I don't see any issues that could be >>> caused by them. For some reason it currently has more passes than the >>> version of -next it's based on! >>> >>> With this series I get the kernel to output to the panel in 0.5s, >>> instead of 2.8s. >>> >>> Regards, >>> >>> Tomeu >>> >>> [0] http://lists.freedesktop.org/archives/dri-devel/2014-August/066527.html >>> >>> [1] https://lkml.org/lkml/2014/5/12/452 >>> >>> [2] https://lkml.org/lkml/2015/6/17/305 >>> >>> [3] http://article.gmane.org/gmane.linux.ports.arm.kernel/277689 >>> >>> [4] https://lkml.org/lkml/2015/7/21/441a >>> >>> [5] https://git.collabora.com/cgit/user/tomeu/linux.git/log/?h=on-demand-probes-v6 >>> >>> [6] http://kernelci.org/boot/all/job/collabora/kernel/v4.2-11902-g25d80c927f8b/ >>> >>> [7] http://kernelci.org/boot/all/job/next/kernel/next-20150903/ >>> >>> Changes in v4: >>> - Added bus.pre_probe callback so the probes of Primecell devices can be >>> deferred if their device IDs cannot be yet read because of the clock >>> driver not having probed when they are registered. Maybe this goes >>> overboard and the matching information should be in the DT if there is >>> one. >> >> Seems overboard to me or at least a separate problem. > > It's a separate problem but this was preventing the series from > working on a few boards. What is the failure? Not booting? Fixing not working would certainly not be overboard. > >> Most clocks have >> to be setup before the driver model simply because timers depend on >> clocks usually. > > Yes, but in this case the apb clocks for the primecell devices are > implemented in a normal platform driver (vexpress_osc_driver), instead > of using CLK_OF_DECLARE. Okay. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
