On Tue, Oct 16, 2018 at 10:31:42AM -0700, Paul Walmsley wrote: > > On 10/16/18 4:01 AM, Thierry Reding wrote: > > On Mon, Oct 15, 2018 at 03:57:35PM -0700, Atish Patra wrote: > > > On 10/10/18 6:49 AM, Thierry Reding wrote: > > > > On Tue, Oct 09, 2018 at 11:51:22AM -0700, Atish Patra wrote: > > > > > +Required properties: > > > > > +- compatible: should be one of > > > > > + "sifive,fu540-c000-pwm0","sifive,pwm0". > > > > What's the '0' in here? A version number? > > > > > > > I think yes. Since fu540 is the first Linux capable RISC-V core, SiFive Guys > > > decided mark it as version 0. > > > > > > @Wesly: Please correct me if I am wrong. > > It seems fairly superfluous to me to have a version number in additon to > > the fu540-c000, which already seems to be the core plus some sort of > > part number. Do you really expect there to be any changes in the SoC > > that would require a different compatible string at this point? If the > > SoC has taped out, how will you ever get a different version of the PWM > > IP in it? > > > > I would expect any improvements or changes to the PWM IP to show up in a > > different SoC generation, at which point it would be something like > > "sifive,fu640-c000" maybe, or perhaps "sifive,fu540-d000", or whatever > > the numbering is. > > > The "0" suffix refers to a revision number for the underlying PWM IP block. > > It's certainly important to keep that version number on the "sifive,pwm0" > compatible string that doesn't have the chip name associated with it. Isn't the hardware identified by "sifive,pwm0" and "sifive,fu540-c000" effectively identical? Is there a need to have two compatible strings that refer to the exact same hardware? > As to whether there could ever be a FU540-C000 part with different IP block > versions on it: FU540-C000 is ultimately a marketing name. While > theoretically we shouldn't have another "FU540-C000" chip with different > peripheral IP block versions on it, I don't think any engineer can guarantee > that it won't happen. I would argue that if at some point there was indeed a chip with the same name but a different IP block version in it, we can figure out what to call it. Sure there are no guarantees, but it's still fairly unlikely in my opinion, so I personally wouldn't worry about this up front. Anyway, I don't feel strongly either way, I'm just pointing out that this is somewhat unusual. If you want to keep it, feel free to. Thierry
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