Am Montag, 13. Juni 2016, 16:04:30 schrieb Douglas Anderson:

Some SD/eMMC PHYs (like the PHY from Arasan that is designed to work
with arasan,sdhci-5.1) need to know the card clock frequency in order to
function properly.  Physically in a SoC this clock is exported from the
SDHCI IP block to the PHY IP block and the PHY needs to know the speed.
Let's export the SDHCI card clock using a standard device tree mechanism
so that the PHY can get access to it and query the card clock frequency.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>

Doug and me talked about how to solve this beforehand, so obviously I'm in 
favour of doing it like this :-)

Reviewed-by: Heiko Stuebner <heiko@sntech.de>