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. > > 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. Great, I'm going to send one more revision rebased on top of v4.3-rc1, without 21 and with the minor changes you suggested, and once Greg is happy I can send the pull request. Thanks, Tomeu > Rob > >> >> 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-v8 >> >> [6] http://kernelci.org/boot/all/job/collabora/kernel/v4.3-rc2-2587-gf92b0ab33d14/ >> >> [7] http://kernelci.org/boot/all/job/next/kernel/next-20150921 >> >> Changes in v6: >> - Drop bus_type.pre_probe and read the periphid in match() instead as >> suggested by Alan Stern. >> - Merge changes to the regulator subsystem's locking so no references >> are leaked between commits. >> >> Changes in v5: >> - Set the pointer to struct device also for AMBA devices >> - Unset the pointer to struct device when the platform device is about >> to be unregistered >> - Increase the reference count of the device before returning from >> of_find_device_by_node() >> - Move the assignment to device_node->device for AMBA devices to another >> commit. >> - Hold a reference to the struct device while it's in use in >> of_device_probe(). >> - Use regulator_class' klist of devices instead of regulator_list to >> store and lookup regulator devices. >> >> 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. >> - Rename of_platform_probe to of_device_probe >> - Use device_node.device instead of device_node.platform_dev >> - Add Kconfig DELAY_DEVICE_PROBES to allow disabling delayed probing in >> machines with initcalls that depend on devices probing at a given time. >> - Start processing deferred probes in device_initcall_sync >> - Also defer probes of AMBA devices registered from the DT as they can >> also request resources. >> >> Changes in v3: >> - Set and use device_node.platform_dev instead of reversing the logic to >> find the platform device that encloses a device node. >> - Drop the fwnode API to probe firmware nodes and add OF-only API for >> now. I think this same scheme could be used for machines with ACPI, >> but I haven't been able to find one that had to defer its probes because >> of the device probe order. >> >> Tomeu Vizoso (22): >> driver core: handle -EPROBE_DEFER from bus_type.match() >> ARM: amba: Move reading of periphid to amba_match() >> of/platform: Point to struct device from device node >> of: add function to allow probing a device from a OF node >> gpio: Probe GPIO drivers on demand >> gpio: Probe pinctrl devices on demand >> regulator: core: Remove regulator_list >> regulator: core: Probe regulators on demand >> drm: Probe panels on demand >> drm/tegra: Probe dpaux devices on demand >> i2c: core: Probe i2c adapters and devices on demand >> pwm: Probe PWM chip devices on demand >> backlight: Probe backlight devices on demand >> usb: phy: Probe phy devices on demand >> clk: Probe clk providers on demand >> pinctrl: Probe pinctrl devices on demand >> phy: core: Probe phy providers on demand >> dma: of: Probe DMA controllers on demand >> power-supply: Probe power supplies on demand >> driver core: Allow deferring probes until late init >> driver core: Start processing deferred probes earlier >> of/platform: Defer probes of registered devices >> >> drivers/amba/bus.c | 88 ++++++------ >> drivers/base/Kconfig | 18 +++ >> drivers/base/dd.c | 35 ++++- >> drivers/clk/clk.c | 3 + >> drivers/dma/of-dma.c | 3 + >> drivers/gpio/gpiolib-of.c | 5 + >> drivers/gpu/drm/drm_panel.c | 3 + >> drivers/gpu/drm/tegra/dpaux.c | 3 + >> drivers/i2c/i2c-core.c | 4 + >> drivers/of/device.c | 61 +++++++++ >> drivers/of/platform.c | 30 +++-- >> drivers/phy/phy-core.c | 3 + >> drivers/pinctrl/devicetree.c | 3 + >> drivers/power/power_supply_core.c | 3 + >> drivers/pwm/core.c | 3 + >> drivers/regulator/core.c | 257 +++++++++++++++++++++++------------- >> drivers/usb/phy/phy.c | 3 + >> drivers/video/backlight/backlight.c | 3 + >> include/linux/device.h | 4 +- >> include/linux/of.h | 1 + >> include/linux/of_device.h | 3 + >> 21 files changed, 386 insertions(+), 150 deletions(-) >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- 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
