Hi Rob,
On 2019-01-21 3:11 p.m., Rob Herring wrote:
On Tue, Jan 15, 2019 at 04:14:21PM -0800, Scott Branden wrote:
Hi Uwe,
On 2019-01-12 7:05 a.m., Uwe Kleine-König wrote:
Hello Scott,
On Fri, Jan 11, 2019 at 01:28:45PM -0800, Scott Branden wrote:
On 2019-01-11 12:48 p.m., Uwe Kleine-König wrote:
On Fri, Jan 11, 2019 at 10:51:14AM +0530, Sheetal Tigadoli wrote:
From: Praveen Kumar B <praveen.b@xxxxxxxxxxxx>
Add new compatible string for new version of pwm-kona
Signed-off-by: Praveen Kumar B <praveen.b@xxxxxxxxxxxx>
Reviewed-by: Ray Jui <ray.jui@xxxxxxxxxxxx>
Reviewed-by: Scott Branden <scott.branden@xxxxxxxxxxxx>
Signed-off-by: Sheetal Tigadoli <sheetal.tigadoli@xxxxxxxxxxxx>
---
Documentation/devicetree/bindings/pwm/brcm,kona-pwm.txt | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Documentation/devicetree/bindings/pwm/brcm,kona-pwm.txt b/Documentation/devicetree/bindings/pwm/brcm,kona-pwm.txt
index 8eae9fe..d37f697 100644
--- a/Documentation/devicetree/bindings/pwm/brcm,kona-pwm.txt
+++ b/Documentation/devicetree/bindings/pwm/brcm,kona-pwm.txt
@@ -3,7 +3,7 @@ Broadcom Kona PWM controller device tree bindings
This controller has 6 channels.
Required Properties :
-- compatible: should contain "brcm,kona-pwm"
+- compatible: should contain "brcm,kona-pwm" or "brcm,kona-pwm-v2"
Is v2 used on a newer generation of kona SoCs? On i.MX these variants
are usually named after the first SoC that came with the new variant. Is
this sensible here, too?
It doesn't make as much sense here as different revs of the IP block are
picked up based on various decisions.
A new SoC could decide to use an old version.
IMHO this is no reason to not use the name of the oldest SoC with this
variant. I don't know how the SoC names are in the broadcom family, but
if they were (in order of age, oldest first):
ant
bear
crocodile
and ant and crocodile use the same IP block we would have
a) with v1, v2:
ant:
compatible = "brcm,kona-pwm-v1";
bear:
compatible = "brcm,kona-pwm-v2";
crocodile:
compatible = "brcm,kona-pwm-v1";
Version numbers can be fine, but generally only as fallbacks as even the
same IP version can be integrated into an SoC differently.
The other issue with versions is they should be meanful such as
corresponding to version tags in IP repos. Often, I'd guess anything
with a 'v1' is just what some s/w person made up. Of course, we only
can really know that for opensource IP or programmable logic IP.
If you do use versions, document what the versioning scheme is.
; and
b) with the SoC naming:
ant:
compatible = "brcm,kona-ant-pwm";
bear:
compatible = "brcm,kona-bear-pwm";
crocodile:
compatible = "brcm,kona-crocodile-pwm", "brcm,kona-ant-pwm";
This is the recommended practice.
(If you want, drop "brcm,kona-crocodile-pwm", but keeping it is more
defensive.)
Generally, you should have "brcm,kona-crocodile-pwm" in case there's
some difference found later. Then you can support the bug or feature
without a DT change.
No DT change would be necessary in any case.
A check against the SOC type in the driver without additional DT
compatibility strings could be done.
I like b) (with "...-crocodile-...") better than a). crocodile using
"...-ant-..." is not more ugly than crocodile using "...-v1". This is
also a tad more robust because if broadcom releases kona-dolphin and
someone finds a minor difference between the IPs used on ant and
crocodile it depends on the order of these events who gets v3, while
with the SoC naming the result is clear.
(OK, and given that "brcm,kona-pwm" is already fixed, both approaches
need slight adaption, but I guess you still get what I meant.)
Thanks for your thoughts and explanation.
It is unfortunate devicetree has no proper guidelines or documentation on
binding naming. In the interest of getting this upstream we can name it
Surely we've captured that somewhere...
Please point me at such documentation.
There is no consistency in kernel drivers from what I have seen.
"brcm, omega-pwm". We can drop kona from the binding name as that
architecture
is really no more - only IP derived from it is - hence the name kona-v2
previously.
Best regards
Uwe
Cheers,
Scott
