Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755451AbZKCWF5 (ORCPT ); Tue, 3 Nov 2009 17:05:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755360AbZKCWF5 (ORCPT ); Tue, 3 Nov 2009 17:05:57 -0500 Received: from brmea-mail-4.Sun.COM ([192.18.98.36]:36674 "EHLO brmea-mail-4.sun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755232AbZKCWF4 (ORCPT ); Tue, 3 Nov 2009 17:05:56 -0500 X-Greylist: delayed 1208 seconds by postgrey-1.27 at vger.kernel.org; Tue, 03 Nov 2009 17:05:56 EST MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <19184.41676.262206.134000@gargle.gargle.HOWL> Date: Tue, 3 Nov 2009 16:38:20 -0500 From: RDH To: Jesse Barnes Cc: linux-kernel@vger.kernel.org Subject: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains X-Mailer: VM 7.19 under Emacs 20.3.1 Reply-To: rdh@east.sun.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2185 Lines: 50 This patch avoids unnecessary PCIe link retraining sequences within the PCIe ASPM common clock setup code by issuing a link retrain command only if we are actually changing the PCIe clock configuration. Signed-off-by: Robert D. Houk --- aspm.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) --- a/drivers/pci/pcie/aspm.c 2009-10-15 20:41:50.000000000 -0400 +++ b/drivers/pci/pcie/aspm.c 2009-11-02 14:29:35.000000000 -0500 @@ -183,6 +183,7 @@ static void pcie_aspm_configure_common_c { int ppos, cpos, same_clock = 1; u16 reg16, parent_reg, child_reg[8]; + u16 lnkctl_ccc_or, lnkctl_ccc_and; unsigned long start_jiffies; struct pci_dev *child, *parent = link->pdev; struct pci_bus *linkbus = parent->subordinate; @@ -205,6 +206,25 @@ static void pcie_aspm_configure_common_c if (!(reg16 & PCI_EXP_LNKSTA_SLC)) same_clock = 0; + /* Check upstream component for Common Clock Config */ + pci_read_config_word(parent, ppos + PCI_EXP_LNKCTL, ®16); + lnkctl_ccc_and = lnkctl_ccc_or = (reg16 & PCI_EXP_LNKCTL_CCC); + + /* Scan downstream component for CCC, all functions */ + list_for_each_entry(child, &linkbus->devices, bus_list) { + cpos = pci_find_capability(child, PCI_CAP_ID_EXP); + pci_read_config_word(child, cpos + PCI_EXP_LNKCTL, ®16); + lnkctl_ccc_and &= (reg16 & PCI_EXP_LNKCTL_CCC); + lnkctl_ccc_or |= (reg16 & PCI_EXP_LNKCTL_CCC); + } + + /* If we want Common Clock OFF and no device/function has it on */ + /* or we want Common Clock ON and every device/function has it on */ + /* then there is no need to retrain PCIe links */ + if (((same_clock == 0) && (lnkctl_ccc_or == 0)) + || ((same_clock == 1) && (lnkctl_ccc_and == PCI_EXP_LNKCTL_CCC))) + return; /* Don't retrain link(s) */ + /* Configure downstream component, all functions */ list_for_each_entry(child, &linkbus->devices, bus_list) { cpos = pci_find_capability(child, PCI_CAP_ID_EXP); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/