Commit de4c928b authored by Michael Ellerman's avatar Michael Ellerman Committed by Paul Mackerras
Browse files

[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 <michael@ellerman.id.au>
Acked-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent e4347dfb

arch/powerpc/platforms/cell/axon_msi.c

+10 −11
Original line number Diff line number Diff line
@@ -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,

				get_order(MSIC_FIFO_SIZE_BYTES));

	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",

		       dn->full_name);

		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,

			MSIC_CTRL_IRQ_ENABLE | MSIC_CTRL_ENABLE |

			MSIC_CTRL_FIFO_SIZE);
@@ -390,7 +388,8 @@ static int axon_msi_probe(struct of_device *device, 
out_free_host:

	kfree(msic->irq_host);

out_free_fifo:

	__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,

			  msic->fifo_phys);

out_free_msic:

	kfree(msic);

out:

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