On Sat, Sep 26, 2015 at 01:17:04PM -0500, Rob Herring 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. > > Your branch is based on -next. Is there any dependence on something in > -next? I want to get this into -next soon, but need a branch not based > on -next. Please send me a pull request with the collected acks and > minor comments I have addressed. Let me review this on Monday and I'll let you know... thanks, greg k-h -- 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
