On Thu, Aug 13, 2009 at 08:52:49AM +1000, Benjamin Herrenschmidt wrote: > On Wed, 2009-08-12 at 23:28 +0100, Russell King wrote: > > > On Thu, Aug 13, 2009 at 07:56:32AM +1000, Benjamin Herrenschmidt wrote: > > > Maybe we can make clock-names non-optional though in the DT as an > > > incentive not to use the simple 1-clock "NULL" path. > > > > We used to pass names. Everyone got the idea that they could ignore > > the struct device argument, and chaos ensued in drivers - people wanted > > to name each of their individual clk structures uniquely, and pass > > clock names, or even struct clk pointers into drivers via platform data. > > Some drivers conditionalized the clock name depending on the SoC they > > were built for in the driver code. > > Hi Russell ! Thanks a lot for your feedback. > > Ok. So I may have misunderstood what names were for. In my mind, those > were the name of the clock input on the HW device :-)
Oh, I do hope I didn't say that was wrong, because that is quite correct. What the idea with passing a NULL 'name' with drivers which only had one input was to force people to avoid using 'name' as the sole way to match. When I originally wrote the AMBA primecell drivers, I did use things like 'UARTCLK' and 'AACICLK' for the clk_get() name - since these were the name on the device, and that really only provided people with a bad example to follow. Especially if you consider that the hardware I had was FPGA based development boards where the clocking layout lent itself well to ignoring the 'dev' argument. > Right. I didn't intend to name the clock sources. I intended to name the > clock -inputs- of a given device. IE. clk_get(dev, name) in my mind > meant "give me the clock provider that feeds my "name" input). That's absolutely the right way to look at it! > Allright but passing a NULL doesn't help for drivers with multiple clock > inputs. IE. How do you want to deal with that ? Do you want to deprecate > the named API and instead provide a new clk_get_for_input(dev, > clk_input) (clk_input could be name or numerical ... tbd) ? NULL certainly doesn't help for drivers with multiple clock inputs. For those, you have to explicitly name the input. To take the example commits I pointed at (the OMAP watchdog driver) OMAP blocks generally have two clock inputs - a functional clock and an interface clock. Originally, the driver was effectively setup to match by clock source name (wdt2_fck, wdt2_ick) which was SoC specific. What the commits did was convert things to looking using the names of the inputs (aka consumer name) - so dev + "fck" and dev + "ick". That results in clkdev looking up the clocks for device "omap_wdt" for inputs "fck" and "ick" respectively. On OMAP1 platforms, there isn't an "ick" as such, so there's a match-any-device dummy "ick" entry. On OMAP2 and OMAP3 (the later revs) there are specific clocks for these, and so the dummy entry is missing. So, the approach I took was: where it is well defined that a device has only one clock input, we pass a NULL name. If it has more than one clock input, we pass the specific consumer name required. > Or am I missing a piece of the puzzle ? Maybe - and since you're just starting to look at clkdev, I'll point out that it's actually not intuitive which way around the "wildcard" matching works in clkdev. The clk_get() arguments aren't the wildcards, they're in the clk_lookup structure. Yes, it seems odd, but if you consider it from the point of view of the platform code wanting to match clocks to a specific set of devices and clock inputs, it's actually the way around that you want. -- Russell King _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
