[PATCH 23/27] clocksource: sh_cmt: Add DT support

Hi Josh,

On Friday 14 February 2014 09:59:51 Josh Cartwright wrote:

On Fri, Feb 14, 2014 at 04:53:08PM +0100, Laurent Pinchart wrote:

quoted

On Friday 14 February 2014 10:58:22 Mark Rutland wrote:

quoted

On Fri, Feb 14, 2014 at 01:00:01AM +0000, Laurent Pinchart wrote:

quoted

+Channels Optional Properties:
+
+  - clock-source-rating: rating of the timer as a clock source
device.
+  - clock-event-rating: rating of the timer as a clock event device.

This feels like a leak of Linux internals. Why do you need this?

You're right, it is. The clock source and clock event ratings are
currently configured through platform data, I'll need to find a way to
compute them in the driver instead.

There's still one piece of Linux-specific data I need though, as I need to
specify for each channel whether to use it as a clock source device, a
clock event device, both of them or none. That's configuration
information that needs to be provided somehow.

Are all the channels equally capable?  We had this problem for the
cadence_ttc timer used on Zynq, and decided to just statically allocate
the first timer to be the clocksource, and the second to be the
clockevent.

No, they're not. The channels can be implemented with different counter 
widths, different available prescalers and source clocks and different power 
management features (not all of them are capable to run in all sleep states).

Also, should the rating really be user configurable?

Probably not. I suppose the rating should be computed by the driver based on 
the source clock frequency, prescaler and counter width. Any help there would 
be very appreciated, I'm pretty new to clock source and clock event devices.

-- 
Regards,

Laurent Pinchart