dmaengine: rcar-dmac: Disable channel 0 when using IOMMU

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@ideasonboard.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index 711da01a200b..a18d16cc4795 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1593,6 +1593,7 @@ 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;
@@ -1612,6 +1613,19 @@ 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)
@@ -1662,7 +1676,8 @@ 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;
         }