From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936225AbdEWLXq (ORCPT ); Tue, 23 May 2017 07:23:46 -0400 Received: from fllnx210.ext.ti.com ([198.47.19.17]:15504 "EHLO fllnx210.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935672AbdEWLXp (ORCPT ); Tue, 23 May 2017 07:23:45 -0400 Subject: Re: [PATCH 3/3] drm/omap: displays: encoder-tpd12s015: Support for hot plug detection To: Laurent Pinchart CC: Peter Ujfalusi , , , , References: <20170515090312.32051-1-peter.ujfalusi@ti.com> <8383085.j5ORBifRWg@avalon> <7be9f55e-7d81-d9c8-9e30-1ddc284137e3@ti.com> <2146476.yg7iIlQTUW@avalon> From: Tomi Valkeinen Message-ID: Date: Tue, 23 May 2017 14:23:37 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <2146476.yg7iIlQTUW@avalon> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="wLI05T84XxNqhxCrf6r0m73MmHLHaR1dF" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --wLI05T84XxNqhxCrf6r0m73MmHLHaR1dF Content-Type: multipart/mixed; boundary="aa3iT8ECnnHDrQFWms8eoJqqMFId6pXlV"; protected-headers="v1" From: Tomi Valkeinen To: Laurent Pinchart Cc: Peter Ujfalusi , airlied@linux.ie, jsarha@ti.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Message-ID: Subject: Re: [PATCH 3/3] drm/omap: displays: encoder-tpd12s015: Support for hot plug detection References: <20170515090312.32051-1-peter.ujfalusi@ti.com> <8383085.j5ORBifRWg@avalon> <7be9f55e-7d81-d9c8-9e30-1ddc284137e3@ti.com> <2146476.yg7iIlQTUW@avalon> In-Reply-To: <2146476.yg7iIlQTUW@avalon> --aa3iT8ECnnHDrQFWms8eoJqqMFId6pXlV Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 23/05/17 13:42, Laurent Pinchart wrote: > Hi Tomi, >=20 > On Tuesday 23 May 2017 13:25:34 Tomi Valkeinen wrote: >> On 23/05/17 12:48, Laurent Pinchart wrote: >>> As the connector code can handle GPIO HPD thanks to patch 2/3, why do= es it >>> have to be duplicated here ? I agree that encoders should support >>> reporting of hotplug events when the HPD signal is connected to an >>> encoder, but if it's connected to a GPIO, it seems to me that it shou= ld >>> be the sole responsibility of the connector code to handle it. >> >> The HPD line goes from the connector to TPD12S015. From TPD12S015 >> another line goes to the SoCs GPIO. >=20 > Isn't it the same signal, just with glitches filtered ? The TPD12S015 i= s an=20 > ESD clamp, level shifter and DC-DC converter, if it wasn't for the two = control=20 > inputs CT_CP_HPD and LS_OE, we could probably do without a driver. I wo= uldn't=20 > add HPD support to this driver, as the chip really can't detect HPD. Yes, it is the same signal, level shifted and filtered, if I'm not mistak= en. The HPD gpio is defined in TPD's DT data. And can we know what is the state of the HPD signal when TPD hasn't configured CT_CP_HPD and LS_OE. Will there be a glitch when CT_CP_HPD is enabled? What if connector-hdmi is already listening to HPD signal at that point? My guess is that having gpio handling just in the connector would work, especially as we set the CT_CP_HPD very early when TPD is being set up. With this series we could probably do a bit more optimized management for CT_CP_HPD, but probably we could still make sure the sequence is such that the CT_CP_HPD is enabled before connector-hdmi registers the ir= q. But that doesn't sound quite correct to me... I do think it's TPD driver's responsibility, and it removes all the "make sure that"'s. Tomi --aa3iT8ECnnHDrQFWms8eoJqqMFId6pXlV-- --wLI05T84XxNqhxCrf6r0m73MmHLHaR1dF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJZJBu5AAoJEPo9qoy8lh71T9IP/1A6B8I0yQ6DzvOBBx32rrp2 z7CWpLaxnwartE/wa7crnhH+OBGeWzRb2xT55lufPm4lpfg5rZ4fpYwGWPXx4Kjq Cc3RN9Ojy2krBydkLPnyjjYaFOda9oAaVKbEZC2dw5DlNPE6G+nBhbeYmmysyiQY vJYfU4FoStJR/ys8qsqPyyMlL4n86dGG4GxpQWBtlbqXJG7UDwfJvX8YIUnupmJW lo0Q1QN12NmKPTVi+2zsxz3KJ8tS/+cPV66m615cXYCiHQzvwDzMFMjAe7ks+rXm 92xl8TgHI2rbrqqRKn0NRG1MRUjrRKxQ67XrHl9pT2Hs4SqpZ0q/AsZMAaL7JVwz 0vXcO9vi/ODk4hqecfjLzoTcEWl08CrA3mIrzTgfiQfiEPHl6japijNUDk2adYi7 I4lWSgu/tZ8se1iLo0d4fmWk/VBuO+lvPd3g0cm7M8SJPUsZ4meEM4Nb++FT3A/K y4XE8pPsE9sQEh0IwNSTHbW549JzsmKpC3HqZNTplNZYP/jMW9zEYouBlTZXot3j g9qjrDl/aD6zpVQ520CoW/lUKkgdyJdtNEqV7fDL8fqKUZpfEakxvJfiX6vlRGWu R0Mqvc8rFB1nN/fWlyX99Z2TIUoFFhdZRv9T9kDtntAr/RS0sDrjHrEQpVBiiDsE O4N674wXawx7bf+5Qroh =Ihy5 -----END PGP SIGNATURE----- --wLI05T84XxNqhxCrf6r0m73MmHLHaR1dF--