On Tuesday, July 28, 2015 03:19:31 PM 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 > fwnode_ensure_device() 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 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). > > With this series I get the kernel to output to the panel in 0.5s, > instead of 2.8s. Can you trim your CC list somewhat, please? I'm definitely going to look at this, but not before then next week. Sorry about that. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
