On Tue, Jun 07, 2016 at 03:44:36PM -0700, Douglas Anderson wrote: > 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 <diand...@chromium.org> > --- > .../devicetree/bindings/mmc/arasan,sdhci.txt | 27 > ++++++++++++++++++++-- > 1 file changed, 25 insertions(+), 2 deletions(-)
Acked-by: Rob Herring <r...@kernel.org>
