On Mon, Aug 19, 2013 at 01:33:18AM +0200, Sebastian Hesselbarth wrote: > On 08/17/2013 06:43 PM, Ezequiel Garcia wrote: > > On Sat, Aug 17, 2013 at 02:29:28PM +0200, Sebastian Hesselbarth wrote: > > > > In fact: I'm not sure. I'm slightly inclined towards considering both > > clocks as clock sources, just as Stephen and Tomasz are proposing. > > > >> But in the end, passing it by DT should be the way to go. I cannot look > >> into the XP datasheet, but I would guess that the exact feature of the > >> ip is not to use _the_ fixed 25MHz clock but XTAL as reference. Maybe > >> one of the free-electrons guys can look it up? > >> > > > > No, the documentation has a register bit for "25Mhz frequency enable", > > for each timer/watchdog. > > > > --- > > > > Anyway, I (almost) agree that the 25Mhz fixed clock must be somehow represented > > in the device-tree, but I'm not exactly sure how. Gregory: maybe you can help > > in this? > > > > In armada-370-xp.dtsi add a 25MHz ref clock node and modify timer node > to reference it: > > cpus { ... }; > > clocks { > ref25M: timer-clock { > compatible = "fixed-clock"; > clock-frequency = <25000000>; > }; > } > > ... > > internal-regs { > timer@20300 { > compatible = "marvell,armada-370-xp-timer"; > reg = <0x20300 0x30>, <0x21040 0x30>; > interrupts = <37>, <38>, <39>, <40>, <5>, <6>; > clocks = <&coreclk 2>, <&ref25M>; > clock-names = "fabric", "fixed"; > }; > }; > > Then use of_clk_get_by_name(np, "fabric") and of_clk_get_by_name(np, > "fixed") respectively. Clock select strategy should be, (a) fail if > no clock, (b) use fabric/fixed if just one clock, (c) use fixed if > both clocks. > > Does that answer your questions? :) > Indeed this looks nice :-) However, I still have a few concerns. I thought we would describe the clock selection in the DT. With the above we return to the single compatible string "armada-370-xp-timer" for both SoCs. I'm not entirely convinced. Isn't it better to distinguish them? -- Ezequiel García, Free Electrons Embedded Linux, Kernel and Android Engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html