Subject: Re: 2.6.37-git17 virtual IO boot failure

From: Nishanth Aravamudan <[email-masked]>
Date: Tue, 18 Jan 2011 14:47:18 -0800

On 18.01.2011 [12:31:52 +1100], Anton Blanchard wrote:
> Hi,
> 
> I was testing 2.6.37-git17 on a POWER7 with virtual IO and hit this:
> 
> Trying to unpack rootfs image as initramfs...
> Freeing initrd memory: 7446k freed
> vio 30000000: Warning: IOMMU dma not supported: mask
> 0xffffffffffffffff, table unavailable
> vio 4000: Warning: IOMMU dma not supported: mask 0xffffffffffffffff,
> table unavailable
> vio 4001: Warning: IOMMU dma not supported: mask 0xffffffffffffffff,
> table unavailable
> vio 4002: Warning: IOMMU dma not supported: mask 0xffffffffffffffff,
> table unavailable
> vio 4004: Warning: IOMMU dma not supported: mask 0xffffffffffffffff,
> table unavailable
> audit: initializing netlink socket (disabled)
> 
> Haven't had a chance to look closer yet.

After debugging a bit, this would appear to be due to the second hunk of
b3c73856ae47d43d0d181f9de1c1c6c0820c4515.

diff --git a/arch/powerpc/kernel/vio.c b/arch/powerpc/kernel/vio.c
index b265405..1b695fd 100644
--- a/arch/powerpc/kernel/vio.c
+++ b/arch/powerpc/kernel/vio.c
@@ -1257,6 +1257,10 @@ struct vio_dev *vio_register_device_node(struct device_node *of_node)
        viodev->dev.parent = &vio_bus_device.dev;
        viodev->dev.bus = &vio_bus_type;
        viodev->dev.release = vio_dev_release;
+        /* needed to ensure proper operation of coherent allocations
+         * later, in case driver doesn't set it explicitly */
+        dma_set_mask(&viodev->dev, DMA_BIT_MASK(64));
+        dma_set_coherent_mask(&viodev->dev, DMA_BIT_MASK(64));

        /* register with generic device framework */
        if (device_register(&viodev->dev)) {

Milton, Sonny, any thoughts?

Thanks,
Nish

-- 
Nishanth Aravamudan <[email-masked]>
IBM Linux Technology Center