From 36f2407fe52c55566221f8c68c8fb808abffd2f5 Mon Sep 17 00:00:00 2001 From: Dean Nelson Date: Tue, 29 Jun 2010 18:12:05 +0000 Subject: [PATCH] e1000e: don't inadvertently re-set INTX_DISABLE Should e1000_test_msi() fail to see an msi interrupt, it attempts to fallback to legacy INTx interrupts. But an error in the code may prevent this from happening correctly. Before calling e1000_test_msi_interrupt(), e1000_test_msi() disables SERR by clearing the SERR bit from the just read PCI_COMMAND bits as it writes them back out. Upon return from calling e1000_test_msi_interrupt(), it re-enables SERR by writing out the version of PCI_COMMAND it had previously read. The problem with this is that e1000_test_msi_interrupt() calls pci_disable_msi(), which eventually ends up in pci_intx(). And because pci_intx() was called with enable set to 1, the INTX_DISABLE bit gets cleared from PCI_COMMAND, which is what we want. But when we get back to e1000_test_msi(), the INTX_DISABLE bit gets inadvertently re-set because of the attempt by e1000_test_msi() to re-enable SERR. The solution is to have e1000_test_msi() re-read the PCI_COMMAND bits as part of its attempt to re-enable SERR. During debugging/testing of this issue I found that not all the systems I ran on had the SERR bit set to begin with. And on some of the systems the same could be said for the INTX_DISABLE bit. Needless to say these latter systems didn't have a problem falling back to legacy INTx interrupts with the code as is. Signed-off-by: Dean Nelson CC: stable@kernel.org Tested-by: Emil Tantilov Signed-off-by: Jeff Kirsher Signed-off-by: David S. Miller --- drivers/net/e1000e/netdev.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c index 71592ed2e686..3e53ca723435 100644 --- a/drivers/net/e1000e/netdev.c +++ b/drivers/net/e1000e/netdev.c @@ -3439,13 +3439,18 @@ static int e1000_test_msi(struct e1000_adapter *adapter) /* disable SERR in case the MSI write causes a master abort */ pci_read_config_word(adapter->pdev, PCI_COMMAND, &pci_cmd); - pci_write_config_word(adapter->pdev, PCI_COMMAND, - pci_cmd & ~PCI_COMMAND_SERR); + if (pci_cmd & PCI_COMMAND_SERR) + pci_write_config_word(adapter->pdev, PCI_COMMAND, + pci_cmd & ~PCI_COMMAND_SERR); err = e1000_test_msi_interrupt(adapter); - /* restore previous setting of command word */ - pci_write_config_word(adapter->pdev, PCI_COMMAND, pci_cmd); + /* re-enable SERR */ + if (pci_cmd & PCI_COMMAND_SERR) { + pci_read_config_word(adapter->pdev, PCI_COMMAND, &pci_cmd); + pci_cmd |= PCI_COMMAND_SERR; + pci_write_config_word(adapter->pdev, PCI_COMMAND, pci_cmd); + } /* success ! */ if (!err) -- 2.20.1