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. 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-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
