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[2603:6081:7b00:6400:99bd:1ec8:6b02:61e8]) by smtp.gmail.com with ESMTPSA id b5-20020ac85405000000b003b6894f7002sm2091109qtq.9.2023.01.19.08.57.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Jan 2023 08:57:46 -0800 (PST) Date: Thu, 19 Jan 2023 11:57:44 -0500 From: Tom Rini To: Simon Glass Cc: Sudeep Holla , Abdellatif El Khlifi , achin.gupta@arm.com, xueliang.zhong@arm.com, Drew.Reed@arm.com, robh@kernel.org, jens.wiklander@linaro.org, ilias.apalodimas@linaro.org, u-boot@lists.denx.de Subject: Re: [PATCH v8 03/10] arm_ffa: introduce Arm FF-A low-level driver Message-ID: <20230119165744.GG631605@bill-the-cat> References: <20230118124923.GB631605@bill-the-cat> <20230118135932.GC631605@bill-the-cat> <20230119163157.GA18384@e121910.cambridge.arm.com> <20230119164652.llh66rapyqqej63f@bogus> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="rZRBnaF0gvoyXYbn" Content-Disposition: inline In-Reply-To: X-Clacks-Overhead: GNU Terry Pratchett X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.39 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.103.6 at phobos.denx.de X-Virus-Status: Clean --rZRBnaF0gvoyXYbn Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jan 19, 2023 at 09:54:29AM -0700, Simon Glass wrote: > Hi Sudeep, >=20 > On Thu, 19 Jan 2023 at 09:46, Sudeep Holla wrote: > > > > Hi Abdellatif, > > > > On Thu, Jan 19, 2023 at 04:31:57PM +0000, Abdellatif El Khlifi wrote: > > > > > > Hi Simon, Tom, > > > > > > The FF-A transport is a SW bus and is not associated to any HW periph= eral or > > > undiscoverable base address. > > > > > > There is only 1 way of discovering the FF-A bus and it's through the = FF-A SW > > > interfaces. The FF-A spec [1] describes this in details. > > > > > > Discovering means gathering information about the FF-A framework such= as: > > > the FF-A version, supported features, secure partitions number and at= tributes. > > > > > > Please refer to the following paragraphs for more details: [2], [3], = [4], [5] > > > > > > The core driver provided by this patchset implements the Setup and di= scovery interfaces > > > in addition to direct messaging. > > > > > > The driver provides ffa_bus_discover() API that allows to discover th= e FF-A bus > > > as described by the spec and in the FF-A driver readme [6]. > > > > > > We expect and highly recommend FF-A users to always discover the FF-A= bus using ffa_bus_discover() API. > > > > > > > Thanks for the details. But IIRC this discussion is not about the FF-A = bus > > and device(partitions) discovery, but the support for FF-A itself. The > > discussion is about where to have a device node to represent the existe= nce of > > FF-A support on a platform. If we are talking about individual partitio= ns > > (devices) in the device tree, then that is pure stupidity as it goes out > > of since with the firmware the moment a partition is added or removed in > > the firmware. > > > > IIUC, the whole discussion was around whether to use FFA_VERSION as the > > discovery mechanism for existence of FF-A support on a platform or you > > have a device node to specify the same. >=20 > No, with respect, that is not quite the situation here. >=20 > > > > Just to be clear, even if it is decided to add a device node, the > > FFA_VERSION must be used to detect the presence of FF-A support and > > return error otherwise. DT node presence is just to satisfy the design > > and must be treated as no auto-confirmation for the presence of FF-A > > support. We are just arguing the device node presence is just redundant, > > but as mentioned before it is up to U-Boot community to make a call on > > what is best. >=20 > U-Boot driver model design already supports this. You can have a > device that binds (from DT) but will not probe because it is not > present / wrong version. Perhaps this was missed in the conversion to > Linux: >=20 > https://u-boot.readthedocs.io/en/latest/develop/driver-model/design.html#= driver-lifecycle >=20 > So there is nothing clever needed here at all and anything you do just > adds confusion and bad precedent. But it's also true that at run-time, within U-Boot, we can modify the device tree we have, with live tree yes? So, the whole series in question here can be done without modifying the base DT and getting in to the further discussions that doing so entails. The assertion is that the software discoverable bus here is sufficient to not need DT, so, OK, lets go. --=20 Tom --rZRBnaF0gvoyXYbn Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQGzBAABCgAdFiEEGjx/cOCPqxcHgJu/FHw5/5Y0tywFAmPJdoUACgkQFHw5/5Y0 tyy7tAv8CJX+X3wcKe23Z+IXgJCFulUKubI1PPNRrr/sa20lNVXhfaj3yZT8a5Il Rm/ejBotq7VP2RXpYPTsU9B/lA2i4IV/u6S7rlfTCx2EdVoPecJwhla0R9eUEOfi lsSYkqKdu/znVcgFQvG7R+24lfXzgUWvNa67BcJI5ypHmzldIQneAu50HVVflaCa jSP3prfmEr/x4p05mBML/pXoGUGmvyvDXn01UqIX/6zFa28QxcDQzvEHYpN9jsAk M4E27vrz6jqUMnLvjsA9MuHU/l1+4iqPFuRC32SR/FKpsAUIx34DHhsIotv16QwZ Q6ZaiHO7O96GMF9A68MHifNwEDLrx2Qd7eqQfgYhfzTC7lVqBReKF/nMxpR1JUMI qoVsvK9YJtBk7tK4q1BDMQiRElZwHfIfNALbP755bH5OsBrSQmweDwlcqt2iF8wo XgAPAFKhLc2qu2icFiQHRy3rqH0up4jeJ5sDgHNlSYrmlWEpxaN7uhmnnGL04sv3 37JDvOmv =vet7 -----END PGP SIGNATURE----- --rZRBnaF0gvoyXYbn--