Rob,

On Wed, Jun 8, 2016 at 1:19 PM, Rob Herring [off-list ref] wrote:

On Tue, Jun 07, 2016 at 03:44:39PM -0700, Douglas Anderson wrote:

quoted

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 in order to function
properly.  Let's expose this clock using a standard device tree
mechanism so that the PHY can get access to and query the card clock.

Need to know the clock freq or need the clock? The former doesn't need
to be in DT.

The PHY needs to know the card clock frequency.  This clock clock
frequency is known nowhere else in the system except the SDHCI driver
since the SDHCI component takes its input clock and applies some
dividers to get the card clock.  In silicon, the SDHCI component and
the PHY are separate and there is a physical clock signal going from
the SDHCI component to the PHY component, so modeling this as a clock
in in the device tree seems sane, doesn't it?

-Doug
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