Return-path: Received: from perceval.ideasonboard.com ([95.142.166.194]:36377 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752606Ab3GQX5c (ORCPT ); Wed, 17 Jul 2013 19:57:32 -0400 From: Laurent Pinchart To: Luciano Coelho Cc: mturquette@linaro.org, Mark Rutland , balbi@ti.com, "grant.likely@linaro.org" , "rob.herring@calxeda.com" , "devicetree-discuss@lists.ozlabs.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-omap@vger.kernel.org" , "linux-wireless@vger.kernel.org" , "linux-arm@vger.kernel.org" Subject: Re: [PATCH] Documentation: dt: bindings: TI WiLink modules Date: Thu, 18 Jul 2013 01:58:17 +0200 Message-ID: <1698879.DLaB5pbe5M@avalon> (sfid-20130718_015750_547135_7D17C261) In-Reply-To: <1372682370.21065.68.camel@cumari.coelho.fi> References: <1372149330-24335-1-git-send-email-coelho@ti.com> <1372425670.21065.61.camel@cumari.coelho.fi> <1372682370.21065.68.camel@cumari.coelho.fi> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi Luciano, On Monday 01 July 2013 15:39:30 Luciano Coelho wrote: > On Fri, 2013-06-28 at 16:21 +0300, Luciano Coelho wrote: > > On Fri, 2013-06-28 at 15:18 +0300, Felipe Balbi wrote: > > > On Fri, Jun 28, 2013 at 03:13:52PM +0300, Luciano Coelho wrote: > > > > On Fri, 2013-06-28 at 14:41 +0300, Felipe Balbi wrote: > > > > > On Fri, Jun 28, 2013 at 02:22:11PM +0300, Luciano Coelho wrote: > > > > > > On Fri, 2013-06-28 at 13:31 +0300, Luciano Coelho wrote: > > > > > > > (fixed Mike's address) > > > > > > > > > > > > > > On Fri, 2013-06-28 at 11:21 +0100, Mark Rutland wrote: > > > > > > > > On Fri, Jun 28, 2013 at 10:53:35AM +0100, Luciano Coelho wrote: > > > > > > > > > On Fri, 2013-06-28 at 10:38 +0100, Mark Rutland wrote: > > > > > > > > > > On Tue, Jun 25, 2013 at 09:35:30AM +0100, Luciano Coelho wrote: > > > > > > > > > > > +Optional properties: > > > > > > > > > > > +-------------------- > > > > > > > > > > > + > > > > > > > > > > > +- refclock: the internal WLAN reference clock frequency > > > > > > > > > > > (required for > > > > > > > > > > > + WiLink6 and WiLink7; not used for WiLink8). Must be > > > > > > > > > > > one of the > > > > > > > > > > > + following: > > > > > > > > > > > + 0 = 19.2 MHz > > > > > > > > > > > + 1 = 26.0 MHz > > > > > > > > > > > + 2 = 38.4 MHz > > > > > > > > > > > + 3 = 52.0 MHz > > > > > > > > > > > + 4 = 38.4 MHz, XTAL > > > > > > > > > > > + 5 = 26.0 MHz, XTAL > > > > > > > > > > > + > > > > > > > > > > > +- tcxoclock: the internal WLAN TCXO clock frequency > > > > > > > > > > > (required for > > > > > > > > > > > + WiLink7 not used for WiLink6 and WiLink8). Must be > > > > > > > > > > > one of the > > > > > > > > > > > + following: > > > > > > > > > > > + 0 = 19.200 MHz > > > > > > > > > > > + 1 = 26.000 MHz > > > > > > > > > > > + 2 = 38.400 MHz > > > > > > > > > > > + 3 = 52.000 MHz > > > > > > > > > > > + 4 = 16.368 MHz > > > > > > > > > > > + 5 = 32.736 MHz > > > > > > > > > > > + 6 = 16.800 MHz > > > > > > > > > > > + 7 = 33.600 MHz > > > > > > > > > > > > > > > > > > > > This looks suspiciously like what we have the common clock > > > > > > > > > > bindings for: > > > > > > > > > > > > > > > > > > > > refclk { > > > > > > > > > > > > > > > > > > > > compatible = "fixed-clock"; > > > > > > > > > > #clock-cells = <0>; > > > > > > > > > > clock-frequency = <19200000>; > > > > > > > > > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > wilink { > > > > > > > > > > > > > > > > > > > > compatible = "ti,wilink7"; > > > > > > > > > > interrupt-parent = <&some_interrupt_controller>; > > > > > > > > > > interrupts = <0 1 1>; > > > > > > > > > > clocks = <&refclk>, <&refclk>; > > > > > > > > > > clock-names = "refclk", "txoclk"; > > > > > > > > > > > > > > > > > > > > }; > > > > > > > > > > > > > > > > > > > > Could you not use them? > > > > > > > > > > > > > > > > > > Hmmm... this actually does look good. But these are > > > > > > > > > internal clocks in the modules, they cannot be accessed from > > > > > > > > > outside. Does it make sense to register them with the clock > > > > > > > > > framework? > > > > > > > > > > > > > > > > Given we already have a common way of describing clocks, I > > > > > > > > think it makes sense to use it -- people already understand > > > > > > > > the common bindings, and it's less code to add add to the > > > > > > > > kernel. I don't think the fact these clocks are internal > > > > > > > > should prevent us from describing them as we would an external > > > > > > > > clock. > > > > > > > > > > > > > > Yes, I agree with you. Thanks for the suggestion! I think it > > > > > > > will look much better. And now that I dug a bit more into the > > > > > > > code, I can see that there are only structs being populated, so > > > > > > > there shouldn't be any other side-effects. > > > > > > > > > > > > Hmmm, one thing that escaped me. Besides the frequency, I also > > > > > > need a boolean that tells if the clock is XTAL or not. I can't > > > > > > figure out how to pass this if I use the generic clock framework. > > > > > > Any suggestions? > > > > > > > > > > Could you use clock-output-names for that ? > > > > > > > > > > XTAL clock: > > > > > > > > > > refclk { > > > > > > > > > > compatible = "fixed-clock"; > > > > > #clock cells = <0>; > > > > > clock-frequency = <19200000>; > > > > > clock-output-names = "xtal"; > > > > > > > > > > }; > > > > > > > > > > non-XTAL clock: > > > > > > > > > > refclk { > > > > > > > > > > compatible = "fixed-clock"; > > > > > #clock cells = <0>; > > > > > clock-frequency = <19200000>; > > > > > clock-output-names = "osc"; /* any better name ? */ > > > > > > > > > > }; > > > > > > > > This starts looking a bit hacky. Using the output name as a flag is > > > > not very pretty. > > > > > > > > I think it would be better to have a separate flag for it in the wlan > > > > node. Like an optional "refclock-xtal" boolean or something. The > > > > downside of this is that we would be adding information about the > > > > clock details in the wilink node. :( > > > > > > > > OTOH, we could add a flag to the generic clock binding? A new optional > > > > boolean that tells whether the clock is XTAL or not: > > > > > > > > refclk { > > > > > > > > compatible = "fixed-clock"; > > > > #clock cells = <0>; > > > > clock-frequency = <19200000>; > > > > clock-xtal; > > > > > > > > }; > > > > > > > > Do you think that would make sense? > > > > > > sure, that looks alright to me. Surely there are other devices out there > > > who want to know if the clock comes from a crystal or not ?!? > > > > Mike, what do you think about this idea? If it sounds okay to you, I can > > cook up a patch adding this flag. > > Hmmm... I started implementing this whole thing, but using these clocks > as "fixed-clock"s is not so straightforward. The problem is that I > would need to register my driver as a clock provider and add the OF > match for "fixed-clock". > > If I do that, all the other "fixed-clock" nodes would be passed to my > driver too, which is wrong. Or, the platform should register the > "fixed-clock" match, but this would be wrong too, since it would find > *my* fixed-clocks. > > The only thing I can come up with is to make a small clock driver (maybe > even inside the WiLink module itself) that registers a new type of > clock, "ti,wilink-clock" or something. But this would really be > overkill, wouldn't it? > > Any other ideas? One possibility would be to just call clk_get_rate() on the clock from the WiLink driver, which would return the fixed frequency specified in DT, and configure the WiLink hardware accordingly. This might be a bit hackish though. -- Regards, Laurent Pinchart