[PATCH 06/11] Documentation: mmc: sdhci-of-arasan: Add ability to export card clock
robh at kernel.org
Fri Jun 10 06:10:52 PDT 2016
On Wed, Jun 08, 2016 at 01:52:20PM -0700, Doug Anderson wrote:
> On Wed, Jun 8, 2016 at 1:19 PM, Rob Herring <robh at kernel.org> wrote:
> > On Tue, Jun 07, 2016 at 03:44:39PM -0700, Douglas Anderson wrote:
> >> 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?
Yes, please just re-word it to make it clear there is a connection. With
Acked-by: Rob Herring <robh at kernel.org>
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