From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomi Valkeinen Subject: Re: Powering OMAP's pins Date: Fri, 28 Sep 2012 09:13:47 +0300 Message-ID: <1348812827.4872.10.camel@lappyti> References: <1348568474.2342.35.camel@deskari> <20120925153806.GC4840@atomide.com> <1348592700.2342.49.camel@deskari> <20120925190721.GD4840@atomide.com> <1348643142.2376.13.camel@deskari> <20120926185912.GG4840@atomide.com> <1348730334.5559.9.camel@lappyti> <20120927184341.GK4840@atomide.com> <20120927185138.GL4840@atomide.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-Z2c0+JE/fFpC5VSWvcpN" Return-path: Received: from na3sys009aog120.obsmtp.com ([74.125.149.140]:48087 "EHLO na3sys009aog120.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751700Ab2I1GOR (ORCPT ); Fri, 28 Sep 2012 02:14:17 -0400 Received: by lagh6 with SMTP id h6so853359lag.19 for ; Thu, 27 Sep 2012 23:13:54 -0700 (PDT) In-Reply-To: <20120927185138.GL4840@atomide.com> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Tony Lindgren Cc: linux-omap , Linus Walleij , Peter Ujfalusi --=-Z2c0+JE/fFpC5VSWvcpN Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2012-09-27 at 11:51 -0700, Tony Lindgren wrote: > * Tony Lindgren [120927 11:45]: > > * Tomi Valkeinen [120927 00:20]: > >=20 > > > I could be mistaken how to HW works (but it does work like that for > > > dss), but sounds to me that uart and gpio drivers (and perhaps some > > > others, I didn't go through all the pins) need similar pin->regulator > > > mapping as you suggested for omapdss. > >=20 > > Yes it seems that there are supply voltage regulator domains > > that are specific to some subsystems. I wonder if these are needed > > in all mux modes, or only when the pins are muxed for that particular > > subsystem? It could be that the documentation is missing some > > information here.. > >=20 > > For example, what happens if you try to use some vdds_dsi powered > > pin in GPIO mode without vdds_dsi? I have not tested that. > Seems like this may provide some clues from "3.6 Power-up and Power-down"= : >=20 > "If the SDI, DSI, or CSI2 and CSIb interfaces are used in standard > LVCMOS mode (that is, GPIO mode) rather than PHY mode (that is, serial > differential mode), then vdds_sdi, vdds_dsi, vdds_csi2, and vdds_csib > may also be connected to vdds. Please, see the recommended SDI, DSI, > CSI2, and CSIb power supply noise of Table 3-5, Recommended Operating > Conditions." >=20 > So based on that it seems that tweaking of the regulators for these > pins is only needed for DSS etc, not for GPIO or serial usage. I don't read the above paragraph the same way. What I think it means is that if, say, a board does not use DSI at all, the vdds_dsi input pin in OMAP could be connected to vdds instead of the normal DSI power from the TWL chip, thus making the OMAP's vdds_dsi "always on". Which means that in some boards the vdds_dsi in TWL is not needed if the pins are used. However, that doesn't mean that the vdds_dsi input is always connected to vdds if the pins are used for non-DSI uses. A board may well use only some of the DSI pins for display, leaving the rest free for other uses. E.g. on omap3 there are 6 DSI pins, and a display panel could well use only 4 of them. If the 2 other pins are used as GPIOs, handling vdds_dsi is still required when using those GPIOs. So I think the above paragraph confirms that the power for the pins is indeed required, and handling for the regulator is needed for GPIOs, uarts, etc. also. Tomi --=-Z2c0+JE/fFpC5VSWvcpN Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAABAgAGBQJQZUAbAAoJEPo9qoy8lh711mgQALB09XwjaGaI2C6JV0p+0mqH dalmcDrzg0R9/lLsxTQ3IvLaR0a831jen9atbSZJbhjNbNKfNnb/G8uONqayFThh DMEiTu6XglPQcTACetlwvmACAVW6MUR+ERA+ztcyJiQ7IjljPbsGF1U1T9WDxuzE 5JUjoceymIHwmexILErXGQuFQFK1P4CRH+6NNoE6b9+HYRL2I0DS5aB6ZHZFjkTz Y9yYN5SOlVeKCrg6JHgjZPGjgcQQAtFou0rpvnvXh0lO40DEMkvzBlTd1x8YoS/2 XSPbyA79G8/O4WT3ICfCcCQwBADdlSaB+QhSlB3eLzST9D4Z3NfRB1lBdigZtSRY cjyfQhzW9Ef+KUOEGfGvZ1i8vYLD9OIaqeG26/9GFT1w+7KoDaTo2sTF+B4AAZ3c I1FYHklevzrEsEbdnHdSNZGdd5dq/5Ly6pj/bvzQutNGruE5F1xV7uQVvD1/QF2G aBGAEDyP3gmuDQ0KjIjqQKIolt70ouDwNxyk7vTPp4k8TkWY2LphUfBN25WxpLGj 7yXmu9Lk8+soflSlrnrqnJCvV39AR6cKBQZC+YPcjxGbXWeYNQO3YnYRhxWsQp8G 6TJUCWIqT7U8OGapmxAzm8HK4XfTfLl3NTepLDxjn/lpslUPzACyVlYyGQxSA3Gz WMIgUA4h+IoDQh+WIIPj =RS7n -----END PGP SIGNATURE----- --=-Z2c0+JE/fFpC5VSWvcpN--