From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753377AbdGJFVz (ORCPT ); Mon, 10 Jul 2017 01:21:55 -0400 Received: from mail-wr0-f194.google.com ([209.85.128.194]:34653 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752449AbdGJFVy (ORCPT ); Mon, 10 Jul 2017 01:21:54 -0400 Date: Mon, 10 Jul 2017 07:21:40 +0200 From: Thierry Reding To: Paul Kocialkowski Cc: linux-arm-kernel@lists.infradead.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, Jonathan Hunter , Stephen Warren , Mikko Perttunen Subject: Re: [PATCH] ARM: tegra: Register host1x node with iommu binding on tegra124 Message-ID: <20170710052140.GA18089@ulmo.fritz.box> References: <20170709163614.6746-1-contact@paulk.fr> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="bp/iNruPH9dso1Pn" Content-Disposition: inline In-Reply-To: <20170709163614.6746-1-contact@paulk.fr> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --bp/iNruPH9dso1Pn Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Jul 09, 2017 at 07:36:14PM +0300, Paul Kocialkowski wrote: > This registers the host1x node with the SMMU (as HC swgroup) to allow > the host1x code to attach to it. It avoid failing the probe sequence, > which resulted in the tegra drm driver not probing and thus nothing > being displayed on-screen. >=20 > Signed-off-by: Paul Kocialkowski > --- > arch/arm/boot/dts/tegra124.dtsi | 1 + > 1 file changed, 1 insertion(+) Thanks for tracking this down. However, I don't think this is an appropriate fix for v4.12 because it requires an update to the DTB in order to preserve functionality, which means we've broken DT ABI. The proper fix I think needs to be to make usage of the IOMMU completely optional in the host1x driver. So I think what happens without this DT change is that the call to iommu_attach_device() fails and we have no way to recover from that. I think what we need to do is to free the domain in that case and make sure we can continue without one. It's probably best to add an error message, or maybe a warning to make sure people are aware. Do you have the time to address this? If not, perhaps Mikko can take a look? Thierry --bp/iNruPH9dso1Pn Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiOrDCAFJzPfAjcif3SOs138+s6EFAlljDuEACgkQ3SOs138+ s6HAcg//SLJLE9otp1B3haMpLaH3yhcjMr2cb5lowgpAsznO9nE1STwEkASQtdWz WOdWYtkdvqRMdgdlreGHkyyqGTU29/bUi6NUOUZwgTeB9fK5wcQMK2MatXY8o2yj QE5/OWe0SulVJekncF2WnLLOUPzkdLzqKPtICGGcHCyvV5ekwe2ULdle8kWTnJm7 hCOaNDNODJmMGcW74tySjXO44H8wTDyXBRso59IHPpQKbMMJLBF9gBfYE4jN2NC9 Rim/gedBGnhwJi/UKhOj7s8ivLRgwL0OoHFxGujXDSpm7G9st/0oIMRMwzH3OLEF VmTHmmHgMRsy/JkaRKPJ32mufS1CDeSrKkAWLS8C7TZXmEQONbI8LDXYBiyTohnC AnKOjPAMnR7f06vVKkRX4sj6OtFl90Hk2N9Vw2C9sp+vlaQB2ZxAohHB+UiIZRoE HfQ6YxrRHCtuTXg9D5Hnz/SdaIK5z5Tu4EG+JYPKmQO/2bmbBXcjUlBohM0TWAKn Gsh3ZI7pJ9/3h59wVJCpC7fCf1i7wXkPliLPfKd6c9Y/6uHgAlrf939OiYAqg7im briy50F7uafFcOiR15zzH0JBMvtIipm+oheAulxD6d5hhLH5hXBEj+zgEZW0uWSG BYHT+kUqd6i9O+k1D2dlxY/xsrRxX/8opdiydefKxx59ftMnJV8= =MZe3 -----END PGP SIGNATURE----- --bp/iNruPH9dso1Pn--