DT/OF On-Demand Device Probing Appears Ready, Likely For Linux 4.4
Written by Michael Larabel in Hardware on 15 October 2015 at 09:15 AM EDT. Add A Comment
A pull request has just been sent in that in turn will target Linux 4.4 for offering on-demand device probing for helping platforms using Device Tree / OpenFirmware.

For the past several months Tomeu Vizoso at Collabora has been working toward on-demand device probing for speeding up the boot process of ARM devices like the NVIDIA Tegra Chromebook.

Tomeu explained the work with an earlier patch series, "I have a problem with the panel on my Tegra Chromebook taking longer than expected to be ready during boot (St├ęphane Marchesin reported what is basically the same issue), 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."

He implemented on-demand device probing for OF/DT and will do probing on demand for GPIO, Pinctrl, Regulator, DRM, i2c, PWM, Backlight, USB PHY, CLK, DMA, Power-Supply, and core drivers. He explains in the patches from the aforelinked Git link, "The goal is to reduce deferred probes to a minimum, as it makes it very cumbersome to find out why a device failed to probe, and can introduce very big delays in when a critical device is probed."

It appears that this on-demand device probing is ready as a pull request has been sent in that would queue it up for integration during the Linux 4.4 merge window.
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