[PATCH 06/11] Documentation: mmc: sdhci-of-arasan: Add ability to export card clock

Doug Anderson dianders at chromium.org
Mon Jun 13 16:05:14 PDT 2016


On Fri, Jun 10, 2016 at 6:10 AM, Rob Herring <robh at kernel.org> wrote:
> On Wed, Jun 08, 2016 at 01:52:20PM -0700, Doug Anderson wrote:
>> Rob,
>> 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
> that,
> Acked-by: Rob Herring <robh at kernel.org>

OK, done.  Thanks for your review!


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