The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d210919dbdc8a82c676cc3e3c370b1802be63124 Mon Sep 17 00:00:00 2001 From: Dmitry Osipenko digetx@gmail.com Date: Sat, 4 Dec 2021 17:58:49 +0300 Subject: [PATCH] drm/tegra: Add back arm_iommu_detach_device()

DMA buffers of 2D/3D engines aren't mapped properly when CONFIG_ARM_DMA_USE_IOMMU=y. The memory management code of Tegra DRM driver has a longstanding overhaul overdue and it's not obvious where the problem is in this case. Hence let's add back the old workaround which we already had sometime before. It explicitly detaches DRM devices from the offending implicit IOMMU domain. This fixes a completely broken 2d/3d drivers in case of ARM32 multiplatform kernel config.

Cc: stable@vger.kernel.org Fixes: fa6661b7aa0b ("drm/tegra: Optionally attach clients to the IOMMU") Signed-off-by: Dmitry Osipenko digetx@gmail.com Signed-off-by: Thierry Reding treding@nvidia.com

diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c index dc04ce329be3..e9de91a4e7e8 100644 --- a/drivers/gpu/drm/tegra/drm.c +++ b/drivers/gpu/drm/tegra/drm.c @@ -22,6 +22,10 @@ #include <drm/drm_prime.h> #include <drm/drm_vblank.h>

+#if IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU) +#include <asm/dma-iommu.h> +#endif + #include "dc.h" #include "drm.h" #include "gem.h" @@ -945,6 +949,17 @@ int host1x_client_iommu_attach(struct host1x_client *client) struct iommu_group *group = NULL; int err;

+#if IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU) + if (client->dev->archdata.mapping) { + struct dma_iommu_mapping *mapping = + to_dma_iommu_mapping(client->dev); + arm_iommu_detach_device(client->dev); + arm_iommu_release_mapping(mapping); + + domain = iommu_get_domain_for_dev(client->dev); + } +#endif + /* * If the host1x client is already attached to an IOMMU domain that is * not the shared IOMMU domain, don't try to attach it to a different