Am 2014-10-13 12:32, schrieb Mark Rutland: > On Sun, Oct 12, 2014 at 07:13:58PM +0100, Stefan Agner wrote: >> This adds an initial device tree to run Linux on the Cortex-M4 on >> Vybrid. >> >> HACK: Because we include armv7-m.dtsi, the soc node happens to >> be before the clock node. This is a problem for vf610-clk.c, which >> tries to optain the fixed clocks defined in the clock nodes. But >> because clock drivers are initialized sequencially, and we do not >> have support for deferred probing, the clock initialization fails >> horrible. >> Move the armv7-m.dtsi include to the bottom to temporarily work >> work around this... >> >> Signed-off-by: Stefan Agner <stefan@xxxxxxxx> >> --- >> Maybe a dummy soc entry in armv7-m.dtsi also helps here. But a >> hack as well. Is it common acceptable that the kernel depends >> on DTS order? > > The kernel should not depend on DTS ordering. We should sort out > deferred probing if there is an issue with it. > > [...] Yes I guess to make this working independent of device tree order, we need to defer probing of vf610-clk when the fixed clocks are not initialized yet. Clock initialization (using CLK_OF_DECLARE) doesn't support EPROBE_DEFER currently. We seem to have already a work around merged because of this. http://thread.gmane.org/gmane.linux.kernel/1635576 Anybody tried to reverse device tree parsing to unveil how many such assumptions are still slumbering? >> + clocks { >> + #address-cells = <1>; >> + #size-cells = <0>; >> + >> + sxosc { >> + compatible = "fixed-clock"; >> + #clock-cells = <0>; >> + clock-frequency = <32768>; >> + }; >> + >> + fxosc { >> + compatible = "fixed-clock"; >> + #clock-cells = <0>; >> + clock-frequency = <24000000>; >> + }; >> + }; > > Please get rid of the clocks node and put these under the root node. > There is nothing special about clocks, and the kernel in no way handles > a clocks node specially. > >> + >> + soc { >> + aips0: aips-bus@40000000 { >> + compatible = "fsl,aips-bus", "simple-bus"; >> + #address-cells = <1>; >> + #size-cells = <1>; >> + reg = <0x40000000 0x70000>; > > Out of curiosity, given that this can be driven as a simple-bus, what do > the aips bus registers allow to be configured? > There is a chapter about the AIPS lite bus in the RM, but according to this the AIPS lite bus itself has no registers by itself. -- Stefan -- 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
