On Sat, Aug 17, 2013 at 02:29:28PM +0200, Sebastian Hesselbarth wrote: > On 08/17/2013 02:09 PM, Tomasz Figa wrote: > > On Friday 16 of August 2013 17:29:00 Stephen Warren wrote: > >> On 08/15/2013 10:27 AM, Ezequiel Garcia wrote: > >> ... > >> > >>> Armada XP > >>> --------- > >>> > >>> Two clock sources are available for timer and watchdog counters: > >>> > >>> Just as explained for the Armada 370, the timer and watchdog counters > >>> decrement rate is a configurable ratio of the L2/coherency fabric > >>> clock. The current clocksource driver implementation chooses an > >>> abritrary ratio. > >>> > >>> In addition to this, both timer and watchdog counter rate can be > >>> configured to use an (internal) 25 MHz fixed clock. > >> > >> So there are clearly two clocks fed into the HW block here. The DT > >> should reflect that. > > > > I fully agree. DT should list all the input clocks that are fed into the > > IP block being described. > > I don't object to the above, but strictly speaking the consequence > would be, that all nodes require a clocks property. For A370/XP timer > the fabric clock is configurable and needs to be passed among core > clocks and timer, the 25MHz clock is not and _could_ be seen as an extra > feature of the core. > 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? -- 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
