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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 <dnelson@redhat.com> CC: stable@kernel.org Tested-by: Emil Tantilov <emil.s.tantilov@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -3439,13 +3439,18 @@ static int e1000_test_msi(struct e1000_adapter *adapter)
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/* disable SERR in case the MSI write causes a master abort */
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pci_read_config_word(adapter->pdev, PCI_COMMAND, &pci_cmd);
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pci_write_config_word(adapter->pdev, PCI_COMMAND,
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pci_cmd & ~PCI_COMMAND_SERR);
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if (pci_cmd & PCI_COMMAND_SERR)
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pci_write_config_word(adapter->pdev, PCI_COMMAND,
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pci_cmd & ~PCI_COMMAND_SERR);
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err = e1000_test_msi_interrupt(adapter);
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/* restore previous setting of command word */
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pci_write_config_word(adapter->pdev, PCI_COMMAND, pci_cmd);
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/* re-enable SERR */
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if (pci_cmd & PCI_COMMAND_SERR) {
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pci_read_config_word(adapter->pdev, PCI_COMMAND, &pci_cmd);
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pci_cmd |= PCI_COMMAND_SERR;
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pci_write_config_word(adapter->pdev, PCI_COMMAND, pci_cmd);
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}
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/* success ! */
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if (!err)
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