From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: [PATCH 1/3] dt-bindings: pwm: kona: Add new compatible for new version pwm-kona Date: Mon, 21 Jan 2019 17:11:05 -0600 Message-ID: <20190121231105.GA928@bogus> References: <1547184076-20521-1-git-send-email-sheetal.tigadoli@broadcom.com> <1547184076-20521-2-git-send-email-sheetal.tigadoli@broadcom.com> <20190111204801.2ytdeblcai7lg3on@pengutronix.de> <20190112150515.i7mwq7rtd62wlifh@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Scott Branden Cc: linux-pwm@vger.kernel.org, Sheetal Tigadoli , Florian Fainelli , Scott Branden , devicetree@vger.kernel.org, Ray Jui , linux-kernel@vger.kernel.org, Thierry Reding , bcm-kernel-feedback-list@broadcom.com, Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Praveen Kumar B , linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org 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-K=F6nig 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-K=F6nig wrote: > > > > On Fri, Jan 11, 2019 at 10:51:14AM +0530, Sheetal Tigadoli wrote: > > > > > From: Praveen Kumar B > > > > > = > > > > > Add new compatible string for new version of pwm-kona > > > > > = > > > > > Signed-off-by: Praveen Kumar B > > > > > Reviewed-by: Ray Jui > > > > > Reviewed-by: Scott Branden > > > > > Signed-off-by: Sheetal Tigadoli > > > > > --- > > > > > 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-v= 2" > > > > Is v2 used on a newer generation of kona SoCs? On i.MX these varian= ts > > > > are usually named after the first SoC that came with the new varian= t. 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 =3D "brcm,kona-pwm-v1"; > > bear: > > compatible =3D "brcm,kona-pwm-v2"; > > crocodile: > > compatible =3D "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 =3D "brcm,kona-ant-pwm"; > > bear: > > compatible =3D "brcm,kona-bear-pwm"; > > crocodile: > > compatible =3D "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. > > = > > 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.=A0 In the interest of getting this upstream we can name it Surely we've captured that somewhere... > = > "brcm, omega-pwm".=A0 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