Douglas Anderson 6582019927 Documentation: mmc: sdhci-of-arasan: Add soc-ctl-syscon for corecfg regs ... As can be seen in Arasan's datasheet [1] there are several "corecfg" settings in their SDHCI IP Block that are supposed to be controlled by software. Although the datasheet referenced is a bit vague about how to access corecfg, in Figure 5 you can see that for Arasan's PHY (a separate component than their SDHCI component) they describe the "phyctrl" registers as being "FROM SOC CTL REG", implying that it's up to the licensee of the Arasan IP block to implement these registers. It seems sane to assume that the "corecfg" registers in their SDHCI IP block works in a similar way for all licensees of the IP Block. Device tree has a model that allows a device to get a reference to random registers located elsewhere in the SoC: sysctl. Let's leverage this model and allow adding a sysctl reference to access the control registers for the Arasan SDHCI PHYs. Having a reference to the control registers doesn't do much for us on its own since the Arasan spec doesn't specify how these corecfg values are laid out in memory. In the SDHCI driver we'll need a map detailing where each corecfg can be found in each implementation. This map can be found using the primary compatible string of the SDHCI device. In that spirit, document that existing rk3399 device trees already have a specific compatible string, though up to now they've always been relying on the driver supporting the generic. Note that since existing devices seem to work fairly well as-is, we'll list the syscon reference as "optional", but it's likely that we'll run into much fewer problems if we can actually set the proper values in the syscon, so it is strongly suggested that any SoCs where we have a map to set the corecfg also include a reference to the syscon. [1]: https://arasan.com/wp-content/media/eMMC-5-1-Total-Solution_Rev-1-3.pdf Signed-off-by: Douglas Anderson <dianders@chromium.org> Acked-by: Rob Herring <robh@kernel.org> Reviewed-by: Heiko Stuebner <heiko@sntech.de> Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>		2016-07-25 10:34:17 +02:00
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bindings	Documentation: mmc: sdhci-of-arasan: Add soc-ctl-syscon for corecfg regs	2016-07-25 10:34:17 +02:00
00-INDEX
booting-without-of.txt	sh: add device tree support and generic board using device tree	2016-03-17 19:46:11 +00:00
changesets.txt
dynamic-resolution-notes.txt
of_unittest.txt
overlay-notes.txt
todo.txt
usage-model.txt