| Message ID | 20100618203630.5781.77777.send-patch@localhost.localdomain |
|---|---|
| State | Awaiting Upstream, archived |
| Delegated to: | David Miller |
| Headers | show |
On Fri, Jun 18, 2010 at 13:36, Dean Nelson <dnelson@redhat.com> wrote: > 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 > > --- > > I forced the msi interrupt test to fail by commenting out the clearing > of FLAG_MSI_TEST_FAILED in e1000_intr_msi_test(). > > drivers/net/e1000e/netdev.c | 13 +++++++++---- > 1 files changed, 9 insertions(+), 4 deletions(-) > Thanks Dean, I have added it to my queue. Cheers, Jeff -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c index 57a7e41..79e38dc 100644 --- a/drivers/net/e1000e/netdev.c +++ b/drivers/net/e1000e/netdev.c @@ -3419,13 +3419,18 @@ 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)
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 --- I forced the msi interrupt test to fail by commenting out the clearing of FLAG_MSI_TEST_FAILED in e1000_intr_msi_test(). drivers/net/e1000e/netdev.c | 13 +++++++++---- 1 files changed, 9 insertions(+), 4 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html