Commit de4c928b authored by Michael Ellerman's avatar Michael Ellerman Committed by Paul Mackerras
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[POWERPC] Avoid DMA exception when using axon_msi with IOMMU

There's a brown-paper-bag bug in axon_msi, we pass the address of our
FIFO directly to the hardware, without DMA mapping it.  This leads to
DMA exceptions if you enable MSI & the IOMMU.

The fix is to correctly DMA map the fifo, dma_alloc_coherent() does
what we want - and we need to track the virt & phys addresses.
Signed-off-by: default avatarMichael Ellerman <>
Acked-by: default avatarBenjamin Herrenschmidt <>
Signed-off-by: default avatarPaul Mackerras <>
parent e4347dfb
......@@ -65,7 +65,8 @@
struct axon_msic {
struct irq_host *irq_host;
__le32 *fifo;
__le32 *fifo_virt;
dma_addr_t fifo_phys;
dcr_host_t dcr_host;
u32 read_offset;
......@@ -91,7 +92,7 @@ static void axon_msi_cascade(unsigned int irq, struct irq_desc *desc)
while (msic->read_offset != write_offset) {
idx = msic->read_offset / sizeof(__le32);
msi = le32_to_cpu(msic->fifo[idx]);
msi = le32_to_cpu(msic->fifo_virt[idx]);
msi &= 0xFFFF;
pr_debug("axon_msi: woff %x roff %x msi %x\n",
......@@ -306,7 +307,6 @@ static int axon_msi_shutdown(struct of_device *device)
static int axon_msi_probe(struct of_device *device,
const struct of_device_id *device_id)
struct page *page;
struct device_node *dn = device->node;
struct axon_msic *msic;
unsigned int virq;
......@@ -338,16 +338,14 @@ static int axon_msi_probe(struct of_device *device,
goto out_free_msic;
page = alloc_pages_node(of_node_to_nid(dn), GFP_KERNEL,
if (!page) {
msic->fifo_virt = dma_alloc_coherent(&device->dev, MSIC_FIFO_SIZE_BYTES,
&msic->fifo_phys, GFP_KERNEL);
if (!msic->fifo_virt) {
printk(KERN_ERR "axon_msi: couldn't allocate fifo for %s\n",
goto out_free_msic;
msic->fifo = page_address(page);
msic->irq_host = irq_alloc_host(of_node_get(dn), IRQ_HOST_MAP_NOMAP,
NR_IRQS, &msic_host_ops, 0);
if (!msic->irq_host) {
......@@ -370,9 +368,9 @@ static int axon_msi_probe(struct of_device *device,
pr_debug("axon_msi: irq 0x%x setup for axon_msi\n", virq);
/* Enable the MSIC hardware */
msic_dcr_write(msic, MSIC_BASE_ADDR_HI_REG, (u64)msic->fifo >> 32);
msic_dcr_write(msic, MSIC_BASE_ADDR_HI_REG, msic->fifo_phys >> 32);
msic_dcr_write(msic, MSIC_BASE_ADDR_LO_REG,
(u64)msic->fifo & 0xFFFFFFFF);
msic->fifo_phys & 0xFFFFFFFF);
msic_dcr_write(msic, MSIC_CTRL_REG,
......@@ -390,7 +388,8 @@ static int axon_msi_probe(struct of_device *device,
__free_pages(virt_to_page(msic->fifo), get_order(MSIC_FIFO_SIZE_BYTES));
dma_free_coherent(&device->dev, MSIC_FIFO_SIZE_BYTES, msic->fifo_virt,
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