[PATCH v1 1/2] gpu: host1x: Add back arm_iommu_detach_device()

[Dmitry Osipenko]

Host1x DMA buffer isn't mapped properly when CONFIG_ARM_DMA_USE_IOMMU=y.
The memory management code of Host1x 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 Host1x device from the offending implicit IOMMU
domain. This fixes a completely broken Host1x DMA in case of ARM32
multiplatform kernel config.

Cc: stable at vger.kernel.org
Fixes: af1cbfb9bf0f ("gpu: host1x: Support DMA mapping of buffers"
Signed-off-by: Dmitry Osipenko <digetx at gmail.com>
---
 drivers/gpu/host1x/dev.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/gpu/host1x/dev.c b/drivers/gpu/host1x/dev.c
index c42ab78327e7..f5b4dcded088 100644
--- a/drivers/gpu/host1x/dev.c
+++ b/drivers/gpu/host1x/dev.c
@@ -22,6 +22,10 @@
 #include <trace/events/host1x.h>
 #undef CREATE_TRACE_POINTS
 
+#if IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)
+#include <asm/dma-iommu.h>
+#endif
+
 #include "bus.h"
 #include "channel.h"
 #include "debug.h"
@@ -263,6 +267,17 @@ static struct iommu_domain *host1x_iommu_attach(struct host1x *host)
 	struct iommu_domain *domain = iommu_get_domain_for_dev(host->dev);
 	int err;
 
+#if IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)
+	if (host->dev->archdata.mapping) {
+		struct dma_iommu_mapping *mapping =
+				to_dma_iommu_mapping(host->dev);
+		arm_iommu_detach_device(host->dev);
+		arm_iommu_release_mapping(mapping);
+
+		domain = iommu_get_domain_for_dev(host->dev);
+	}
+#endif
+
 	/*
 	 * We may not always want to enable IOMMU support (for example if the
 	 * host1x firewall is already enabled and we don't support addressing
-- 
2.33.1