From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dean Nelson Subject: [net-next-2.6 PATCH] e1000e: don't inadvertently re-set INTX_DISABLE Date: Fri, 18 Jun 2010 16:36:30 -0400 Message-ID: <20100618203630.5781.77777.send-patch@localhost.localdomain> Cc: Andy Gospodarek To: netdev@vger.kernel.org, Jeff Kirsher Return-path: Received: from mx1.redhat.com ([209.132.183.28]:1025 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750913Ab0FRUgd (ORCPT ); Fri, 18 Jun 2010 16:36:33 -0400 Sender: netdev-owner@vger.kernel.org List-ID: 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 --- 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(-) 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)