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The device tree standard states that when the status property is not present under a node, the okay value is assumed. There are many reasons for doing the same, the number of strings in the device tree, default power management functionality, etc. are a few of the reasons. In general, after a few rounds of discussions [1] there are few options one could take when dealing with SoC dtsi and board dts a. SoC dtsi provide nodes as a super-set default (aka enabled) state and to prevent messy board files, when more boards are added per SoC, we optimize and disable commonly un-used nodes in board-common.dtsi b. SoC dtsi disables all hardware dependent nodes by default and board dts files enable nodes based on a need basis. c. Subjectively pick and choose which nodes we will disable by default in SoC dtsi and over the years we can optimize things and change default state depending on the need. While there are pros and cons on each of these approaches, the right thing to do will be to stick with device tree default standards and work within those established rules. So, we choose to go with option (a). Lets cleanup defaults of am654 SoC dtsi before this gets more harder to cleanup later on and new SoCs are added. The dtb generated is identical with the patch and it is just cleanup to ensure we have a clean usage model NOTE: There is a known risk of omission that new board dts developers might miss reviewing both the board schematics in addition to all the DT nodes of the SoC when setting appropriate nodes status to disable or reserved in the board dts. This can expose issues in drivers that may not anticipate an incomplete node (example: missing appropriate board properties) being in an "okay" state. These cases are considered bugs and need to be fixed in the drivers as and when identified. [1] https://lore.kernel.org/linux-arm-kernel/20201027130701.GE5639@atomide.com/ Signed-off-by: Nishanth Menon <nm@ti.com> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com> Reviewed-by: Tony Lindgren <tony@atomide.com> Cc: Jyri Sarha <jsarha@ti.com> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com> Cc: Peter Ujfalusi <peter.ujfalusi@ti.com> Cc: Tony Lindgren <tony@atomide.com> Link: https://lore.kernel.org/r/20201113211826.13087-2-nm@ti.com |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.