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The General Register Files are an area of registers containing a lot of single-bit settings for numerous components as well full components like usbphy control. Therefore all used components are accessed via the syscon provided by the grf nodes or from the sub-devices created through the simple-mfd created from the grf node. Some settings are not used by anything but will need to be set up according to expectations on the kernel side. Best example is the force_jtag setting, which defaults to on and results in the soc switching the pin-outputs between jtag and sdmmc automatically depending on the card-detect status. This conflicts heavily with how the dw_mmc driver expects to do its work and also with the clock-controller, which has most likely deactivated the jtag clock due to it being unused. So far the handling of this setting was living in the mach-rockchip code for the arm32-based rk3288 but that of course doesn't work for arm64 socs and would also look ugly for further arm32 socs. Also always disabling this setting is quite specific to linux and its subsystems, other operating systems might prefer other settings, so that the bootloader cannot really set a sane default for all. So introduce a top-level driver for the grf that handles these settings that need to be a certain way but nobody cares about. Other needed settings might surface in the future and can then be added here, but only as a last option. Ideally general GRF settings should be handled in the driver needing them. Signed-off-by: Heiko Stuebner <heiko@sntech.de> Reviewed-by: Douglas Anderson <dianders@chromium.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.