linux-kernel - [RFC PATCH v1 5/6] drm/nouveau: tegra: Universally avoid implicit DMA backing with IOMMU

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Message-Id: <20180726231624.21084-6-digetx@gmail.com>
Date:   Fri, 27 Jul 2018 02:16:23 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mikko Perttunen <cyndis@...si.fi>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Joerg Roedel <joro@...tes.org>,
        Nicolas Chauvet <kwizart@...il.com>
Cc:     devicetree@...r.kernel.org, nouveau@...ts.freedesktop.org,
        iommu@...ts.linux-foundation.org, dri-devel@...ts.freedesktop.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v1 5/6] drm/nouveau: tegra: Universally avoid implicit DMA backing with IOMMU

Implicit backing DMA with IOMMU breaks Nouveau on Tegra, the current
approach with detaching device from IOMMU that was added in commit
b59fb482b522 ("drm/nouveau: tegra: Detach from ARM DMA/IOMMU mapping")
works only for arm32 which has the CONFIG_ARM_DMA_USE_IOMMU, but not for
arm64 which doesn't have that config option. Drivers core now allows to
avoid the implicit backing, that is a universal solution unlike the
current variant with the detaching.

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/gpu/drm/nouveau/nouveau_platform.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/nouveau/nouveau_platform.c b/drivers/gpu/drm/nouveau/nouveau_platform.c
index 039e23548e08..0b57f4f9b638 100644
--- a/drivers/gpu/drm/nouveau/nouveau_platform.c
+++ b/drivers/gpu/drm/nouveau/nouveau_platform.c
@@ -90,6 +90,7 @@ MODULE_DEVICE_TABLE(of, nouveau_platform_match);
 struct platform_driver nouveau_platform_driver = {
 	.driver = {
 		.name = "nouveau",
+		.no_implicit_iommu = true,
 		.of_match_table = of_match_ptr(nouveau_platform_match),
 	},
 	.probe = nouveau_platform_probe,
-- 
2.18.0