On Tue, Oct 13, 2015 at 2:57 PM, Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx> wrote: > On 26 September 2015 at 20:17, Rob Herring <robh@xxxxxxxxxx> wrote: >> On 09/21/2015 09:02 AM, Tomeu Vizoso 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][6][7] with these patches on top of today's >>> linux-next (20150921) to kernelci.org and I don't see any issues that >>> could be caused by them. >>> >>> With this series I get the kernel to output to the panel in 0.5s, >>> instead of 2.8s. >> >> I think we're pretty close other than some minor comments. I would like >> to see ack's from Greg and some reviewed-bys from others. The subsystem >> changes are minor and there has been plenty of chance to comment, so I >> don't think acks from all subsystems are needed. > > Hi Rob, > > I'm not sure we are going to get much more feedback by just waiting or > resending what has been sent so many times. Agreed. > Did you have in mind specific people you wanted to see reviewed-bys from? Mainly Greg. Please send me a pull req. I want to get this into -next and can always drop it if there is further review. 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
