From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: ARM topic: Is DT on ARM the solution, or is there something better? Date: Mon, 18 Nov 2013 17:06:28 +0100 Message-ID: <20131118160626.GN26046@ulmo.nvidia.com> References: <52644A9E.3060007@wwwdotorg.org> <20131118122644.GA26046@ulmo.nvidia.com> <20131118134022.26EE7C409EC@trevor.secretlab.ca> <20131118135727.GD14306@sirena.org.uk> <20131118152920.GL26046@ulmo.nvidia.com> <20131118155022.GB28334@sirena.org.uk> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="GEn4szYucjS2InE7" Return-path: Content-Disposition: inline In-Reply-To: <20131118155022.GB28334-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mark Brown Cc: Grant Likely , Stephen Warren , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "ksummit-2013-discuss-cunTk1MwBs98uUxBSJOaYoYkZiVZrdSR2LY78lusg7I@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: devicetree@vger.kernel.org --GEn4szYucjS2InE7 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Nov 18, 2013 at 03:50:22PM +0000, Mark Brown wrote: > On Mon, Nov 18, 2013 at 04:29:21PM +0100, Thierry Reding wrote: > > On Mon, Nov 18, 2013 at 01:57:27PM +0000, Mark Brown wrote: >=20 > > > You'd need something class based like USB, there's such massive > > > variation in what the hardware is trying to do and the tradeoffs. A = big > > > issue is that especially with I2C many of the devices are primarily > > > analogue devices implemnted in larger processes where the cost of add= ing > > > additional digital logic can have a noticeable effect on the area and > > > hence cost of the silicon. >=20 > > My comments were mostly regarding the interface controllers. Those which > > generate the same bus transactions but need different drivers on every > > SoC. I suspect that the same costs don't apply (or at least not to the > > same extent) to SoCs. >=20 > Oh, right. In that space I suspect you'd face apathy on the part of > vendors for switching away from their existing validated and deployed > IPs - probably the best shot would be a freely licensed reference > implementation that people could pick up if they wanted. It's plausible > that some of the vendors might do so for SPI where there are a bunch of > chips that don't have DMA/FIFOs yet and so could possibly benefit from > performance and feature gains but without that sort of benefit it's hard > to see what would be persuasive for the vendors. Part of my point was that you could possibly still use the same IP with only a modified (standard) register interface. That way no licensing of third party IP would be needed. You'd only need to rewrite parts of the IP to make it look (and behave) like the standard one. That's exactly how 16550-compatible UARTs work, isn't it? Or even the way that USB (EHCI, ...) work. There's a standardize register interface, possibly with a way for vendor-specific extensions, but the interface itself doesn't need to be licensed, so there are no additional costs to supporting the standard interface. There are only the advantages of being able to reuse a well-tested body of code. Thierry --GEn4szYucjS2InE7 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJSijsBAAoJEN0jrNd/PrOh3RUP/jvbkCm4NPn4LJP8UJd+qZmj u8+d43tdrS2Lf9qc6C4V9o/zt3amQ1B24dF+PWWh/wwjOEH1jTqj7cveq0QLuycP SjgO+r04lvw40Ih5jJ8CsEJ/Qkj1e0I/x46OJ1DH0QrebgoRIs41tpAIEGHGxiKo n1FW3LTg/mOgUiQZ/w0TPd4Ya45JsThzO8ovp85Flq9lm9EuImNVDLnEoJf5m0lV DA7m7G3To2yad/aFkZ1/lcQGLoueKQ8hwdRfF3M/LQhgFlfas2D7pMJDzbUKWu3D n58oymVzlYbzhjSDBQ+KLWZBc1bm8ca4/u4ZxtMqiZxz0Hiee6myzNpgMuebbNkO kr+Lkh/yBLqDxp7OWCF8yFfl5DPVcrYB6HsZ12WgMWLzuTAWBidYuty4C5+RHqvY PAzwzCuZNJh9wSkUAfv1UIb/TXjCR0sVEbCdypl6X5B5no8cgda43kJN1aYy9nFG cs+6OySrl8PrpzpPKnsqlZqBGByVdIWXFVR/cF49BpcTBaYFauN+9laVO3tC929v l0u1ZTlImf+fpKt4mGjJaAn17YlKzcewPBux88sFC4MmizC9mrNOsaTsZGQK5aAh C9NkQSPtWSbyilva23MMZ/O4AU/Pc9gDaS3HRralD4JzSC38adQuXYmUoDYC9AxR TeuV51Pcmw7i57XeqobP =SVX6 -----END PGP SIGNATURE----- --GEn4szYucjS2InE7-- -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html