On Tue, Oct 16, 2018 at 03:20:34PM -0700, Atish Patra wrote: > On 10/16/18 3:04 PM, Thierry Reding wrote: > > 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? > > Yes. > > Is there a need to have two compatible strings > > that refer to the exact same hardware? > > > > The DT in the hardware has only sifive,pwm0. I have added > "sifive,fu540-c000" as that was concluded as the correct compatible string > from platform level interrupt controller patch(PLIC) discussion. > > (http://lists.infradead.org/pipermail/linux-riscv/2018-August/001135.html) > > "sifive,pwm0" is required to until all the Unleashed SoC gets an updated > firmware with correct compatible string "sifive,fu540-c000". I agree this is > a mess. But we have to carry it until all every DT(corresponding to each > driver) is finalized. I guess SiFive will release a firmware update that > contains all the updated DT once that is done. We can get rid of all the > redundant compatible strings at that time. I don't want to repeat compatible string discussions on each and every IP block. I already have to do this with some vendors. The RiscV vendors' needs and design flow are a bit different from traditional SoC vendors AIUI for the last discussion. If you need to do something that doesn't follow normal conventions, that's fine. Just please document a convention that works for you. This should explain where the '0' above comes from for example. And I'm not a fan of s/w folks making up version numbers. Rob
