From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: [RFC PATCH 6/8] dts: coresight: Clean up the device tree graph bindings Date: Wed, 13 Jun 2018 07:57:47 -0600 Message-ID: References: <1527858967-16047-1-git-send-email-suzuki.poulose@arm.com> <1527858967-16047-7-git-send-email-suzuki.poulose@arm.com> <20180612204802.GA15817@rob-hp-laptop> <5448BBB7-93FE-400F-9D87-FABF5DE0539C@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Suzuki K Poulose Cc: Matt Sealey , "linux-arm-kernel@lists.infradead.org" , "mathieu.poirier@linaro.org" , Sudeep Holla , Mark Rutland , "frowand.list@gmail.com" , Charles Garcia-Tobin , John Horley , "mike.leach@linaro.org" , "coresight@lists.linaro.org" , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" List-Id: devicetree@vger.kernel.org On Wed, Jun 13, 2018 at 7:35 AM, Suzuki K Poulose wrote: > Hi Matt, > > Thanks for your comments, responses inline. > > On 13/06/18 13:49, Matt Sealey wrote: >> >> Suzuki, >> >> Why not use =E2=80=9Cunit=E2=80=9D? >> >> I believe we had this discussion years ago about numbering serial ports >> and sdhci (i.e. how do you know it=E2=80=99s UART0 or UART1 from just th= e address? >> Some SoC=E2=80=99s don=E2=80=99t address sequentially *or* in a forward = direction) - I >> believe it=E2=80=99s not exactly codified in ePAPR, not am I sure where = it may be >> otherwise, but it exists. > > > We have different situation here. We need to know *the port number* as > understood by the > hardware, so that we can enable *the specific* port for a given path. > >> >> I agree with Rob on the slave-mode nonsense, this is an SPI controller >> concept weirdly stuffed into a directed graph which implicitly tells you= the >> data direction - it=E2=80=99s a rooted tree (just like DT!). OF graph is not directional. All links must be bi-directional and in fact dtc checks that now. The parent node should know the numbering and direction of each port. > Btw, the "slave-mode" is not a standard DT graph binding. It is not part = of > the > generic DT graph binding. In fact the generic bindings stay away from the > direction > aspect and explicitly mentions the same. I really don't like slave-mode nor coresight,hwid. I would prefer to see getting rid of both and splitting ports into "in-ports" and "out-ports" nodes instead of a single "ports" node. Then you don't need any of these properties and reg can be used as the hwid. Rob