On Tue, Oct 16, 2018 at 03:20:34PM -0700, Atish Patra wrote:

On 10/16/18 3:04 PM, Thierry Reding wrote:

quoted

On Tue, Oct 16, 2018 at 10:31:42AM -0700, Paul Walmsley wrote:

quoted

On 10/16/18 4:01 AM, Thierry Reding wrote:

quoted

On Mon, Oct 15, 2018 at 03:57:35PM -0700, Atish Patra wrote:

quoted

On 10/10/18 6:49 AM, Thierry Reding wrote:

quoted

On Tue, Oct 09, 2018 at 11:51:22AM -0700, Atish Patra wrote:

quoted

+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

quoted

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