A still unconfirmed hardware bug prevents the IPMMU microTLB 0 to be
flushed correctly, resulting in memory corruption. DMAC 0 channel 0 is
connected to microTLB 0 on currently supported platforms, so we can't
use it with the IPMMU. As the IOMMU API operates at the device level we
can't disable it selectively, so ignore channel 0 for now if the device
is part of an IOMMU group.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
---
drivers/dma/sh/rcar-dmac.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
As this patch works around an IOMMU bug in a DMA engine driver it would
benefit from review from IOMMU developers.
Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Magnus Damm <magnus.damm@xxxxxxxxx>
diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index d345d3d81813..e0bf38a7284e 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1595,6 +1595,7 @@ static int rcar_dmac_probe(struct platform_device *pdev)
DMA_SLAVE_BUSWIDTH_2_BYTES | DMA_SLAVE_BUSWIDTH_4_BYTES |
DMA_SLAVE_BUSWIDTH_8_BYTES | DMA_SLAVE_BUSWIDTH_16_BYTES |
DMA_SLAVE_BUSWIDTH_32_BYTES | DMA_SLAVE_BUSWIDTH_64_BYTES;
+ unsigned int channels_offset = 0;
struct dma_device *engine;
struct rcar_dmac *dmac;
struct resource *mem;
@@ -1614,6 +1615,19 @@ static int rcar_dmac_probe(struct platform_device *pdev)
if (ret < 0)
return ret;
+ /*
+ * A still unconfirmed hardware bug prevents the IPMMU microTLB 0 to be
+ * flushed correctly, resulting in memory corruption. DMAC 0 channel 0
+ * is connected to microTLB 0 on currently supported platforms, so we
+ * can't use it with the IPMMU. As the IOMMU API operates at the device
+ * level we can't disable it selectively, so ignore channel 0 for now if
+ * the device is part of an IOMMU group.
+ */
+ if (pdev->dev.iommu_group) {
+ dmac->n_channels--;
+ channels_offset = 1;
+ }
+
dmac->channels = devm_kcalloc(&pdev->dev, dmac->n_channels,
sizeof(*dmac->channels), GFP_KERNEL);
if (!dmac->channels)
@@ -1664,7 +1678,8 @@ static int rcar_dmac_probe(struct platform_device *pdev)
INIT_LIST_HEAD(&dmac->engine.channels);
for (i = 0; i < dmac->n_channels; ++i) {
- ret = rcar_dmac_chan_probe(dmac, &dmac->channels[i], i);
+ ret = rcar_dmac_chan_probe(dmac, &dmac->channels[i],
+ i + channels_offset);
if (ret < 0)
goto error;
}
--
2.0.5
--
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