From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomi Valkeinen Subject: Re: [PATCH 2/2] ARM: OMAP2+: fix dpll round_rate() to actually round Date: Wed, 26 Feb 2014 13:48:20 +0200 Message-ID: <530DD484.5040703@ti.com> References: <1389944699-27962-1-git-send-email-tomi.valkeinen@ti.com> <1389944699-27962-3-git-send-email-tomi.valkeinen@ti.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============8451189893934424629==" Return-path: 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: Paul Walmsley , Tero Kristo Cc: Tony Lindgren , linux-omap@vger.kernel.org, Mike Turquette , linux-arm-kernel@lists.infradead.org List-Id: linux-omap@vger.kernel.org --===============8451189893934424629== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="FehtNJi3Ppj594xmGTKHG8s8DfTELLXhA" --FehtNJi3Ppj594xmGTKHG8s8DfTELLXhA Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 20/02/14 21:30, Paul Walmsley wrote: > On Wed, 19 Feb 2014, Paul Walmsley wrote: >=20 >> On Fri, 17 Jan 2014, Tomi Valkeinen wrote: >> >>> This patch adds a simple method of rounding: during the iteration, th= e=20 >>> code keeps track of the closest rate match. If no exact match is foun= d,=20 >>> the closest is returned. >> >> So that's one possible rounding policy; maybe it works fine for a disp= lay=20 >> interface PLL, at least for some values of "closest rate". But anothe= r=20 >> might be "only allow a selection from a set of pre-determined rates=20 >> characterized by the silicon validation team". Or another rounding=20 >> function might need to select a more distant rate that minimizes jitte= r,=20 >> EMI, or power consumption. =20 >=20 > Thought about this some more. Do you only need this for the DSS PLL, o= r=20 > do you need it for one of the core OMAP PLLs? >=20 > If the former, then how about modifying your patch to create a separate= =20 > round_rate function that's only used for the DSS PLL that implements th= e=20 > behavior that you want? >=20 > That would eliminate any risk of impacting other users on the system. = And=20 > would also allow this change to get into the codebase much faster, sinc= e=20 > there's no need for clk API changes, etc. The DSS internal PLLs are handled by the DSS driver, which does all kinds of iteration to find good clocks. This patch is for a dedicated display PLL, present on, for example, BeagleBoneBlack. If you think that's better approach, I can take a look how it can be done (I'm not too familiar with the clock framework). Or maybe there's a possibility to have a flag of some kind, which allows rounded values to be returned? That sounds like an easy addition too. Note that the same change is needed for DT and non-DT boots. Having separate round function would mean create a new clock "driver" (i.e. compatibility string), wouldn't it? Adding a flag sounds easier. Tomi --FehtNJi3Ppj594xmGTKHG8s8DfTELLXhA Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQIcBAEBAgAGBQJTDdSEAAoJEPo9qoy8lh71jXUP/0pMOC6Fm8DkJE1ZmrE1lvwe o6jYoFd8yuDVvd9cA2WGnbPuiyjsuNY8qKD5CZNWghQevyViTzK8yB5k5tyGKD2Y P/7c8woLpUiA95Qv8EGy4CN92/0l/WFtR/azDQkZTVXZNIVpC8zT1Y9Rw9nmkbHX yrD+bZ+ai4O+L1X0QIgYhtarHiMaBduYWxImkY4eSxQNVl6fneycBbwiM8+Mmf9l WEATIkK8ypMNajbNQ2hS6wLvKnDu1RE1uiP03DRx3OkBjKJaetsKRgum/ZeTLWQd lqnVxYVQU6ctyG8iyjYOkMD1ZMT4uXER3OkiY7FaL9rnmxH2cX+TDW08Pmb2QQY/ s8fH5+N5FKvx0BpVv3qhWqPyB1YKoi463FnSGxqrkP4WoPTiDENQq2JR4q9OkJSi NLRZrSUS0n7GGpC8WYowbR7si4MqsU2fjKynLKaMut5cG1nSVJRPR94hqzA2MKI+ +kxJxqYBGa+e1+ciXxT+OYdBmeQHGZd/cvatZO8N9qgjFlQyZzgC87jo3HYRkL9Z X/ABF+n9sndZJkQjvFTJMb0QUJCFbiOXeeU9UMmQZ63vrSrmF20qy6kFXLsSsma4 6gTYuUaA73zFh57E5qYEU3rXneOUBPohYsj6FfYFvqFEw/3j47oLlziQe/4a7PuZ /KXWf54oY7s3Klgw4wMg =Cs24 -----END PGP SIGNATURE----- --FehtNJi3Ppj594xmGTKHG8s8DfTELLXhA-- --===============8451189893934424629== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============8451189893934424629==--