Re: [RFC][PATCH 1/2] ARM: OMAP4: clock: Add device tree support forAUXCLKs
From: Nishanth Menon
Date: Tue Apr 09 2013 - 17:54:40 EST
On 15:49-20130409, Nishanth Menon wrote:
> On 10:43-20130409, Tony Lindgren wrote:
> > * Tony Lindgren <tony@xxxxxxxxxxx> [130409 09:54]:
> > > * Roger Quadros <rogerq@xxxxxx> [130409 03:00]:
> > > > On 04/05/2013 06:58 PM, Tony Lindgren wrote:
> > > > >
> > > > > Can't you just use the clock name there to get it?
> > > >
> > > > In device tree we don't pass around clock names. You can either get
> > > > a phandle or an index to the clock.
> > > >
> > > > e.g. Documentation/devicetree/bindings/clock/imx31-clock.txt
> > >
> > > Yes I understand that. But the driver/clock/omap driver can just
> > > remap the DT device initially so the board specific clock is
> > > found from the clock alias table. Basically initially a passthrough
> > > driver that can be enhanced to parse DT clock bindings and load
> > > data from /lib/firmware.
> > Actually probably the driver/clock/omap can even do even less
> > initially. There probably even no need to remap clocks there.
> > As long as the DT clock driver understands that a board specific
> > auxclk is specified in the DT it can just call clk_add_alias() so
> > the driver will get the right auxclk from cclock44xx_data.c.
> > Then other features can be added later on like to allocate a
> > clock entirely based on the binding etc.
> I did try to have an implementation for cpufreq using clock nodes.
> unfortunately, device tree wont let me have arguments of strings :(
> So, I am unable to do clock = <&clk mpu_dpll>;
> instead, I am forced to do clock = <&clk 249>;
> Here is an attempt on beagleXM - adds every clock node to the list.
> Tons of un-necessary prints added to give an idea - see log:
> Would an cleaned up version be good enough as a step #1 of transition?
Here is yet another revision -> here I am trying to avoid the risk of
folks messing up indexing. for example: using an older DTB with newer
kernel, clocks being inserted into existing list etc. to prevent these,
we add an "DT_ID" for omap clock nodes, and use it to uniquely identify
the clock node. We try to minimize(not avoidable with integer indexing)
mistakes during development/productization.