From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35036C43381 for ; Thu, 21 Mar 2019 15:45:40 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 036E9218E2 for ; Thu, 21 Mar 2019 15:45:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="nZBdVizO"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="IWVA21m+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 036E9218E2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type:Cc: List-Subscribe:List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: In-Reply-To:MIME-Version:References:Message-ID:Subject:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=mB9gZFzCOaZjHWtD1xF4y+VeWHxoJBi9e745sfhE8DQ=; b=nZBdVizOor8ut91jrGBexw7N5 nL+B0GVqN+soqHBQx42pDBeXYs7xYZrH0gRKBojd4oFDVUXJuFG+gyC9ARU13emDfOHMCysjIPtdm /u3T08o7a5a1ZkB8VbeclFRrAYrYb4GxlcvnTRYH+3sezP/dKLtA4mFLhuT9XlUFsDNLFzaVI7thh xA8E9WJv5MpFg3C33ycIjLKouSG19KUlpbRdmOlexj1HHj0ODD9UXOviEkLMh56PqSZFUP9/p74H/ sniOFIju5mZOpbwtH7rbJXmwWdPQEwivRd0RAOWd2Cyq8JU6E9VTExyJx5hko/9ZmIRP2awTIrgJH qFp0w73NQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h6zsq-0000cg-Bq; Thu, 21 Mar 2019 15:45:32 +0000 Received: from merlin.infradead.org ([2001:8b0:10b:1231::1]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1h6zso-0000cA-4x for linux-arm-kernel@bombadil.infradead.org; Thu, 21 Mar 2019 15:45:30 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=yl3xMbKUaH67jUbdS5Snuhrml10lt+B356TrUzsaiZI=; b=IWVA21m+X6ccREMVvEv3DjRBc c2zmPsJU8t9aioraDXrhcnnVmkGxD/6Xo5Hm4ckjXdysNa3NZPcC33MFtXZkTWYJD9Mfq06GjHYdJ 1Jtn9R46tLqQihYcdbdQwyD1KKiFp8kNSwA2DBuqoXD4aM2axDj5nm285GywatHpuB/3RCUGHVgYo 5cUnV/V3n2xNI4ZxV40D2+E217E9jiiagxBcMie3vH4clxULGT0D84hltUY7H3PCjMOP7HN1Kuy2D g8p+nSg9Gg4+uGqWTpKBhhomEJSOoFrpCRD9ZmZaU4Qa7TsbW4sKFQd9uRp/4ksOgNuw/RXASn3vr VglRptBsw==; Received: from relay7-d.mail.gandi.net ([217.70.183.200]) by merlin.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1h6zsk-0006ZA-Iu for linux-arm-kernel@lists.infradead.org; Thu, 21 Mar 2019 15:45:28 +0000 X-Originating-IP: 185.94.189.187 Received: from localhost (unknown [185.94.189.187]) (Authenticated sender: maxime.ripard@bootlin.com) by relay7-d.mail.gandi.net (Postfix) with ESMTPSA id 7CF4F2000B; Thu, 21 Mar 2019 15:44:53 +0000 (UTC) Date: Thu, 21 Mar 2019 16:44:52 +0100 From: Maxime Ripard To: =?utf-8?B?TcOlbnMgUnVsbGfDpXJk?= Subject: Re: [PATCH] drm/sun4i: hdmi: add support for ddc-i2c-bus property Message-ID: <20190321154452.noq3l44x3mshljvy@flea> References: <20190311134713.25876-1-mans@mansr.com> <20190311154702.eslw5ccol44vxcmy@flea> <20190314154105.o6r7hzeuiyajxh7v@flea> <20190318155013.lge2x2cp5hvyz52f@flea> <20190319123445.w6q7vzr3qtgkejwj@flea> MIME-Version: 1.0 In-Reply-To: User-Agent: NeoMutt/20180716 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190321_114526_874107_5E617F34 X-CRM114-Status: GOOD ( 38.30 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Airlie , Chen-Yu Tsai , linux-arm-kernel@lists.infradead.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Content-Type: multipart/mixed; boundary="===============0050032512588568672==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============0050032512588568672== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="d7t26a5uorjmt2ya" Content-Disposition: inline --d7t26a5uorjmt2ya Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Mar 19, 2019 at 12:48:19PM +0000, M=E5ns Rullg=E5rd wrote: > Maxime Ripard writes: > > > On Mon, Mar 18, 2019 at 04:23:56PM +0000, M=E5ns Rullg=E5rd wrote: > >> Maxime Ripard writes: > >> > >> > On Thu, Mar 14, 2019 at 04:09:13PM +0000, M=E5ns Rullg=E5rd wrote: > >> >> Maxime Ripard writes: > >> >> > >> >> > On Mon, Mar 11, 2019 at 04:11:06PM +0000, M=E5ns Rullg=E5rd wrote: > >> >> >> Maxime Ripard writes: > >> >> >> > >> >> >> > Hi! > >> >> >> > > >> >> >> > On Mon, Mar 11, 2019 at 01:47:13PM +0000, Mans Rullgard wrote: > >> >> >> >> Sometimes it is desirabled to use a separate i2c controller f= or ddc > >> >> >> >> access. This adds support for the ddc-i2c-bus property of the > >> >> >> >> hdmi-connector node, using the specified controller if provid= ed. > >> >> >> >> > >> >> >> >> Signed-off-by: Mans Rullgard > >> >> >> >> --- > >> >> >> >> drivers/gpu/drm/sun4i/sun4i_hdmi.h | 1 + > >> >> >> >> drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c | 37 ++++++++++++++++= +++++++--- > >> >> >> >> 2 files changed, 35 insertions(+), 3 deletions(-) > >> >> >> >> > >> >> >> >> diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi.h b/drivers/gpu= /drm/sun4i/sun4i_hdmi.h > >> >> >> >> index b685ee11623d..b08c4453d47c 100644 > >> >> >> >> --- a/drivers/gpu/drm/sun4i/sun4i_hdmi.h > >> >> >> >> +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi.h > >> >> >> >> @@ -269,6 +269,7 @@ struct sun4i_hdmi { > >> >> >> >> struct clk *tmds_clk; > >> >> >> >> > >> >> >> >> struct i2c_adapter *i2c; > >> >> >> >> + struct i2c_adapter *ddc_i2c; > >> >> >> >> > >> >> >> >> /* Regmap fields for I2C adapter */ > >> >> >> >> struct regmap_field *field_ddc_en; > >> >> >> >> diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers= /gpu/drm/sun4i/sun4i_hdmi_enc.c > >> >> >> >> index 061d2e0d9011..5b2fac79f5d6 100644 > >> >> >> >> --- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c > >> >> >> >> +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c > >> >> >> >> @@ -212,7 +212,7 @@ static int sun4i_hdmi_get_modes(struct dr= m_connector *connector) > >> >> >> >> struct edid *edid; > >> >> >> >> int ret; > >> >> >> >> > >> >> >> >> - edid =3D drm_get_edid(connector, hdmi->i2c); > >> >> >> >> + edid =3D drm_get_edid(connector, hdmi->ddc_i2c ?: hdmi->i2c= ); > >> >> >> > > >> >> >> > You can't test whether ddc_i2c is NULL or not... > >> >> >> > > >> >> >> >> if (!edid) > >> >> >> >> return 0; > >> >> >> >> > >> >> >> >> @@ -228,6 +228,28 @@ static int sun4i_hdmi_get_modes(struct d= rm_connector *connector) > >> >> >> >> return ret; > >> >> >> >> } > >> >> >> >> > >> >> >> >> +static struct i2c_adapter *sun4i_hdmi_get_ddc(struct device = *dev) > >> >> >> >> +{ > >> >> >> >> + struct device_node *phandle, *remote; > >> >> >> >> + struct i2c_adapter *ddc; > >> >> >> >> + > >> >> >> >> + remote =3D of_graph_get_remote_node(dev->of_node, 1, -1); > >> >> >> >> + if (!remote) > >> >> >> >> + return ERR_PTR(-EINVAL); > >> >> >> >> + > >> >> >> >> + phandle =3D of_parse_phandle(remote, "ddc-i2c-bus", 0); > >> >> >> >> + of_node_put(remote); > >> >> >> >> + if (!phandle) > >> >> >> >> + return NULL; > >> >> >> >> + > >> >> >> >> + ddc =3D of_get_i2c_adapter_by_node(phandle); > >> >> >> >> + of_node_put(phandle); > >> >> >> >> + if (!ddc) > >> >> >> >> + return ERR_PTR(-EPROBE_DEFER); > >> >> >> >> + > >> >> >> >> + return ddc; > >> >> >> > > >> >> >> > ... Since even in (most) error cases you're returning a !NULL = pointer. > >> >> >> > > >> >> >> >> +} > >> >> >> >> + > >> >> >> >> static const struct drm_connector_helper_funcs sun4i_hdmi_co= nnector_helper_funcs =3D { > >> >> >> >> .get_modes =3D sun4i_hdmi_get_modes, > >> >> >> >> }; > >> >> >> >> @@ -575,6 +597,12 @@ static int sun4i_hdmi_bind(struct device= *dev, struct device *master, > >> >> >> >> goto err_disable_mod_clk; > >> >> >> >> } > >> >> >> >> > >> >> >> >> + hdmi->ddc_i2c =3D sun4i_hdmi_get_ddc(dev); > >> >> >> >> + if (IS_ERR(hdmi->ddc_i2c)) { > >> >> >> > >> >> >> ... which is checked here. > >> >> >> > >> >> >> The property is optional, so the idea was to return null in that= case > >> >> >> and use the built-in controller. If the property exists but som= e error > >> >> >> occurs, we want to abort rather than proceed with the fallback w= hich > >> >> >> almost certainly won't work. > >> >> >> > >> >> >> Maybe I got something wrong in that logic. > >> >> > > >> >> > Indeed, I just got confused. I guess returning ENODEV in such a c= ase, > >> >> > and testing for that, would make things more obvious. > >> >> > >> >> There's also a case I hadn't thought of: property exists but isn't a > >> >> valid phandle. What do you think is the correct action in that cas= e? > >> > > >> > I think we would have that one covered. of_parse_phandle will return > >> > !NULL, but then of_get_i2c_adapter_by_node will return NULL since we > >> > wouldn't have an associated i2c adapter to the bogus phandle, and you > >> > are checking for that already. > >> > >> of_parse_phandle() doesn't differentiate between a missing property and > >> an existing non-phandle value. The following cases are possible with > >> this patch: > >> > >> - ddc-i2c-bus points to valid i2c controller node: use this for ddc > >> - no ddc-i2c-bus property: return NULL, use internal i2c > >> - ddc-i2c-bus exists but isn't a phandle: likewise > >> - ddc-i2c-bus points to a non-i2c-controller node: EPROBE_DEFER > >> > >> The last two cases obviously mean the devicetree is invalid, so perhaps > >> it doesn't matter much what happens then. I don't think it's possible > >> to distinguish between a well-formed phandle pointing to some bogus no= de > >> and a good one where the i2c driver hasn't been probed yet. > > > > Ah, I see what you mean now. Yeah, there's not much we can do against > > a wrong / corrupted DT. The DT validation would help prevent the third > > case, and possibly the fourth, but that's basically the only thing we > > can do. > > We need to return -EPROBE_DEFER in the case that everything is fine but > the i2c driver hasn't been probed yet. From here, that is > indistinguishable from of_parse_phandle() returning a completely bogus > node. That's unfortunate, but if we start to not trust the DT content, we have far worse to deal with. > If the ddc-i2c-bus property doesn't contain a phandle at all, we could > either return an error or fall back to the internal i2c. The patch does > the latter because that's less code. I don't think that's any worse > than aborting entirely in terms of user experience. I'm totally fine with the latter behaviour as well. And like I said, the DT validation can help us prevent that case from happening entirely at compilation time. Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com --d7t26a5uorjmt2ya Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRcEzekXsqa64kGDp7j7w1vZxhRxQUCXJOxdAAKCRDj7w1vZxhR xS+zAQDxq4cfhKfuYhOOZhCrJ4Cl+VnyDRy4NYKaZDx5O8IbeQEAlow7BVxj+qw1 xcb65MrjOp2xDUpBNZAG3yxcFeW6BwE= =P+oR -----END PGP SIGNATURE----- --d7t26a5uorjmt2ya-- --===============0050032512588568672== 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 --===============0050032512588568672==--