From mboxrd@z Thu Jan 1 00:00:00 1970 From: zonque@gmail.com (Daniel Mack) Date: Tue, 19 Feb 2013 18:32:09 +0100 Subject: Question about fixed-clock In-Reply-To: <20130219172246.11471.14635@quantum> References: <5122BF88.1050007@gmail.com> <51234B8E.2000504@gmail.com> <20130219172246.11471.14635@quantum> Message-ID: <5123B719.2080300@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 19.02.2013 18:22, Mike Turquette wrote: > Quoting Daniel Mack (2013-02-19 01:53:18) >> Hi Fabio, >> Hi Afzal, >> >> On 19.02.2013 02:33, Fabio Estevam wrote: >>> On Mon, Feb 18, 2013 at 8:55 PM, Daniel Mack wrote: >>>> Hi, >>>> >>>> This might be a stupid question, but I'm somehow stuck here. I'm using a >>>> driver with the following DTS sub-node: >>>> >>>> ref25: ref25M { >>>> compatible = "fixed-clock"; >>>> #clock-cells = <0>; >>>> clock-frequency = <25000000>; >>>> }; >>>> >>>> clock-generator at 0 { >>>> /* ... */ >>>> #clock-cells = <1>; >>>> clocks = <&ref25>; >>>> } >>>> >>>> The device driver for clock-generator uses something like the following >>>> call to get its clock: >>>> >>>> clk = of_clk_get(np, 0); >>>> >>>> but the return value is ERR_PTR(-ENOENT) and I also can't find this >>>> clock in the clk debugfs tree. >>>> >>>> This is on a OMAP/AM33xx device with kernel 3.8-rc7 plus the -next tips >>>> of arm-soc and omap, but with no other special clock options selected in >>>> the config. Is there anything I'm missing to correctly instantiate the >>>> dummy clock? >>> >>> Have you registered it with clk_register_fixed_rate() ? >>> >>> In imx we use imx_clk_fixed, which in turns call clk_register_fixed_rate(). >>> >>> Take a look at arch/arm/mach-imx/clk-imx51-imx53.c for a reference. >> >> Hmm no, I didn't do anything else than adding it to the DT in the first >> place, hoping that a driver will pick it up and add the clock for me. >> But it turns out that of_clk_init() is not called at all on my platform. >> >> I'm doing this now from omap_generic_init() and it works. If that's an >> appropriate place to call it, I can provide a patch. >> > > You can provide a patch, but your example above is for a dummy clock, > correct? No, it's a real clock with a fixed frequency on the board, which feeds another clock chip. I thought this is what fixed-clock is for, just like what a fixed-regulator does? Or how would you describe such a thing in DT, in order to use it as input to another device? > It would be best to post your patch along with a real-world > use for calling of_clk_init(). Not sure what you mean exactly, but the patch is attached. However, I still think I lack some understanding here - the fact that compatible strings have to be passed explicitly from generic code feels wrong. Thanks, Daniel -------------- next part -------------- A non-text attachment was scrubbed... Name: 0001-ARM-OMAP-generic-add-call-to-of_clk_init.patch Type: text/x-patch Size: 1336 bytes Desc: not available URL: