On 30 July 2015 at 05:06, Rob Herring <robherring2@xxxxxxxxx> wrote: > On Tue, Jul 28, 2015 at 8:19 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 >> 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. > > Seems like a minor change to me. > >> 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. > > Generally, I think this looks pretty good. It is simple and the error > path is simply falling back to deferred probe. > > One overall comment is I'm not so sure if fwnode_ensure_device > shouldn't just be of_ensure_device. At least currently, it looks like > all the calling locations are DT specific functions anyway. There's > very little logic within the function to really benefit sharing with > ACPI. It is basically just a call to of_platform_device_find and then > bus_probe_device. I expect the get functions will always call into > DT/ACPI specific functions which can then call the firmware specific > device find function. That's fine with me. I just went that way because I assumed the plan was for subsystems to move to consume fw data through fwnode and drop as much fw-specific code as possible. But I have just looked at fwnode_get_named_gpiod and the OF and ACPI code paths are so dissimilar that I guess that's not so and would be better to do as you say. Thanks, Tomeu _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
