From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932644AbbIYQsF (ORCPT ); Fri, 25 Sep 2015 12:48:05 -0400 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:49659 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932234AbbIYQsC (ORCPT ); Fri, 25 Sep 2015 12:48:02 -0400 Date: Fri, 25 Sep 2015 09:47:26 -0700 From: Mark Brown To: Sascha Hauer Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Liam Girdwood , kernel@pengutronix.de, "Rafael J. Wysocki" , Viresh Kumar Message-ID: <20150925164726.GI30445@sirena.org.uk> References: <20150925090724.GH7858@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ZZc4RZLlj7DA0l+0" Content-Disposition: inline In-Reply-To: <20150925090724.GH7858@pengutronix.de> X-Cookie: NOBODY EXPECTS THE SPANISH INQUISITION! User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: 70.35.39.2 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: Re: Voltage setting on chained regulators, how? X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on mezzanine.sirena.org.uk) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ZZc4RZLlj7DA0l+0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Sep 25, 2015 at 11:07:24AM +0200, Sascha Hauer wrote: > Any idea how such a scenario could be implemented? The regulator > framework already has some idea of supply regulators, but it only takes > care of en/disabling the supplies and will not change the voltage on the > supplies. Should this be implemented in the regulator framework? Some > first experiments brought me into a locking hell quite fast. It's just a case of implementation, but yes the locking is fun. I don't think it's that big a deal to rethink it, it's partly complicated since the existing locking is designed to be really simple and easy to review. > For added fun ideally we want to put the LDOs in bypass mode instead of > configuring them for minimum dropout. The bypass mode doesn't work for > the 1.2GHz operating point though since the ripple on the switching > regulator gets too high. So we can't just statically configure bypass > mode but have to enable it dynamically based on the operating points. I suspect you always want the LDO in there to clean the supply up, it's just a more serious issue when more power is being drawn. Having a DCDC doing most of the voltage drop for efficiency with a LDO to clean up the output of the DCDC is pretty common. --ZZc4RZLlj7DA0l+0 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJWBXqdAAoJECTWi3JdVIfQAWIH+gILdDFJ0Qwvqz7KQ5YNl1/n WHqiMVu9OryFzxcGHbszd+0UA+KVHRZtjNMqjwbT4/JoImiyLqgjJhJgWd92pupA YeRmw/xyCLHnR/0jrjhA1e+eIlUnoya5pqbAb7/rwLVdnY8vyo1NIGd2dnjGfEjP XjctB8emYPj/FeaHyKxy0BJYyWv2nhxVYXaB/wZteeVPbGHPfJVwRWpO12tkwMfV w3Y5F6hMbhWRfKbMCh1RfVvFBUuQFK854AyqRrCAefuQNCI8GIL4Ocgo9VjRjPjr 6PFAMUTS3r7isXWiPzl9f/0sreuNodrWd459JkPWnvWBfr1o/nWzzFzCf+4XL68= =Axoe -----END PGP SIGNATURE----- --ZZc4RZLlj7DA0l+0--