* Stephen Warren wrote: > Thierry Reding wrote at Saturday, March 03, 2012 3:54 PM: > > I'm confused. If I know exactly that the hardware is Tegra30 (which it > > definitely should be if I include tegra30.dtsi), then why list "tegra20-pwm" > > as compatible? > > > > Or did you mean to list tegra30-pwm as compatible value in the PWM driver? > > Standard practice is to list the exact model of the HW as the first entry > in compatible in the .dts file: > > nvidia,tegra30-pwm > > This is so that the DT always describes exactly which HW model is actually > present, so that if HW-model-specific WARs/... are required in the future, > the DT already lists that information up-front. > > Then additionally list any older HW models that this HW is also compatible > with: > > nvidia,tegra20-pwm > > > This allows the driver to list just nvidia,tegra20-pwm but still bind > to DT nodes that are for later HW. > > So, in other words, you end up with the following in the .dts/.dtsi file: > > compatible = "nvidia,tegra30-pwm", "nvidia,tegra20-pwm"; Okay, that makes sense now. For some reason I thought you were suggesting to put the same into tegra20.dtsi as well. I'll add nvidia,tegra30-pwm to the compatible list in the driver and list both values in the tegra30.dtsi. Thanks for explaining. > > > Could you also write binding documentation, in particular explaining > > > what the two pwm-cells are specifically for Tegra: > > > > > > Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt > > > > > > (although perhaps that'd be part of the previous patch which implements > > > the driver) > > > > Actually for Tegra the values would be those documented in the generic > > binding because Tegra uses of_pwm_simple_xlate(). Does it still make sense to > > add a Tegra-specific binding? > > There should still be a Tegra-specific binding. Without it, there's no > definite way to know whether the "standard" properties actually apply, > or someone simply forgot to document it. Understood. I assume that both the Tegra20 and Tegra30 variants should have explicit bindings then as well, right? Thierry
Attachment:
pgpa6GZmLyk4h.pgp
Description: PGP signature
