[patch 01/36] atl1: disable broken 64-bit DMA

Greg KH
2007-12-13T06:37:24Z

[-- Attachment #1: atl1-disable-broken-64-bit-dma.patch --]
[-- Type: text/plain, Size: 2706 bytes --]

2.6.22-stable review patch. If anyone has any objections, please let us
know.

------------------

From: Luca Tettamanti <kronos.it@gmail.com>

atl1: disable broken 64-bit DMA

[ Upstream commit: 5f08e46b621a769e52a9545a23ab1d5fb2aec1d4 ]

The L1 network chip can DMA to 64-bit addresses, but multiple descriptor
rings share a single register for the high 32 bits of their address, so
only a single, aligned, 4 GB physical address range can be used at a time.
As a result, we need to confine the driver to a 32-bit DMA mask, otherwise
we see occasional data corruption errors in systems containing 4 or more
gigabytes of RAM.

Signed-off-by: Luca Tettamanti <kronos.it@gmail.com>
Signed-off-by: Jay Cliburn <jacliburn@bellsouth.net>
Acked-by: Chris Snook <csnook@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/net/atl1/atl1_main.c | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)

--- a/drivers/net/atl1/atl1_main.c
+++ b/drivers/net/atl1/atl1_main.c
@@ -2097,21 +2097,26 @@ static int __devinit atl1_probe(struct p
struct net_device *netdev;
struct atl1_adapter *adapter;
static int cards_found = 0;
- bool pci_using_64 = true;
int err;

err = pci_enable_device(pdev);
if (err)
return err;

- err = pci_set_dma_mask(pdev, DMA_64BIT_MASK);
+ /*
+ * The atl1 chip can DMA to 64-bit addresses, but it uses a single
+ * shared register for the high 32 bits, so only a single, aligned,
+ * 4 GB physical address range can be used at a time.
+ *
+ * Supporting 64-bit DMA on this hardware is more trouble than it's
+ * worth. It is far easier to limit to 32-bit DMA than update
+ * various kernel subsystems to support the mechanics required by a
+ * fixed-high-32-bit system.
+ */
+ err = pci_set_dma_mask(pdev, DMA_32BIT_MASK);
if (err) {
- err = pci_set_dma_mask(pdev, DMA_32BIT_MASK);
- if (err) {
- dev_err(&pdev->dev, "no usable DMA configuration\n");
- goto err_dma;
- }
- pci_using_64 = false;
+ dev_err(&pdev->dev, "no usable DMA configuration\n");
+ goto err_dma;
}
/* Mark all PCI regions associated with PCI device
* pdev as being reserved by owner atl1_driver_name
@@ -2176,7 +2181,6 @@ static int __devinit atl1_probe(struct p

netdev->ethtool_ops = &atl1_ethtool_ops;
adapter->bd_number = cards_found;
- adapter->pci_using_64 = pci_using_64;

/* setup the private structure */
err = atl1_sw_init(adapter);
@@ -2193,9 +2197,6 @@ static int __devinit atl1_probe(struct p
*/
/* netdev->features |= NETIF_F_TSO; */

- if (pci_using_64)
- netdev->features |= NETIF_F_HIGHDMA;
-
netdev->features |= NETIF_F_LLTX;

/*

--