[PATCH 4/9] clk: Add clock driver for mb86s7x

Jassi Brar jaswinder.singh at linaro.org
Fri Nov 21 08:36:51 PST 2014

On 21 November 2014 20:04, Arnd Bergmann <arnd at arndb.de> wrote:
> On Friday 21 November 2014 18:52:47 Jassi Brar wrote:
>> On 21 November 2014 18:33, Arnd Bergmann <arnd at arndb.de> wrote:
>> > On Thursday 20 November 2014 20:36:15 Vincent Yang wrote:
>> >> +#define __DTS_MB86S70_CLK_H
>> >> +
>> >> +#define MB86S70_CRG11_ALW      0
>> >> +#define MB86S70_CRG11_DDR3     1
>> >> +#define MB86S70_CRG11_MAIN     2
>> >> +#define MB86S70_CRG11_CA15     3
>> >> +#define MB86S70_CRG11_HDMI     4
>> >> +#define MB86S70_CRG11_DPHY     5
>> >> +
>> >> +#define MB86S70_CRG11_UNGPRT   8
>> >>
>> >
>> > The clock driver doesn't seem to use those macros at all, how does the
>> > driver know which clock you are referring to?
>> >
>> That was just an attempt to make a bit verbose the controller
>> instance. Instead of specifying controller:=4, it reads better
>> controller:=MB86S70_CRG11_HDMI in the clock DT nodes. The clock driver
>> simply fills in controller+domain+port of the given clock into mailbox
>> payload.
> See my other comments on the clock nodes. If these are hardware properties,
> just leave them as numbers in the DT, the header files are only used to
> establish an interface between the binding and the driver in case there
> is no sensible way to express which one you have.
OK, I'll hardcode numbers there.

>> Only MB86S70_CRG11_UNGPRT is marked to mean one special (non-maskable)
>> port on the controller, which the clock driver does make use of.
> Is this the actual port number that is known to be non-maskable?
Yes the clock comes out of the controller and is also the parent of
other 8 independently maskable clock ports of the domain.
 The firmware on remote master, lets say, don't wanna be bothered by
the clock topology. Even for set-rate the onus is on Linux to request
only appropriate rates at appropriate times so that other devices are
not messed up.

> How about adding a property to the clock node to mark the logical
> controller nonmaskable (in case you go for #clock-cells=2)?
> For the #clock-cells=3 case, you should probably just hardcode this
> in the driver based on the compatible string.
The SoC has 6 controllers, each controller has 16domains and each
domain has 8+1 ports. Instead of 864 clocks, we wanted to populate
only clocks that some device actually use (some clocks seem unused in
this patchset but we have users that will be upstreamed later).
The remote f/w can't manage inter-dependencies and expect Linux to
send only appropriate requests on port basis, so we populate ports as
tiny independent clock controllers with single clock output.


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