netdev - RE: [PATCH net v2 2/2] net: ixgbe: Use new PCI_DEV_FLAGS_NO_RELAXED

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Message-ID: <87618083B2453E4A8714035B62D67992B4094F7A@FMSMSX105.amr.corp.intel.com>
Date:   Thu, 17 Aug 2017 14:17:49 +0000
From:   "Tantilov, Emil S" <emil.s.tantilov@...el.com>
To:     Ding Tianhong <dingtianhong@...wei.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "alexander.duyck@...il.com" <alexander.duyck@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linuxarm@...wei.com" <linuxarm@...wei.com>
Subject: RE: [PATCH net v2 2/2] net: ixgbe: Use new
 PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag

>-----Original Message-----
>From: linux-kernel-owner@...r.kernel.org [mailto:linux-kernel-
>owner@...r.kernel.org] On Behalf Of Ding Tianhong
>Sent: Wednesday, August 16, 2017 8:25 PM
>To: davem@...emloft.net; Kirsher, Jeffrey T <jeffrey.t.kirsher@...el.com>;
>keescook@...omium.org; linux-kernel@...r.kernel.org;
>sparclinux@...r.kernel.org; intel-wired-lan@...ts.osuosl.org;
>alexander.duyck@...il.com; netdev@...r.kernel.org; linuxarm@...wei.com
>Cc: Ding Tianhong <dingtianhong@...wei.com>
>Subject: [PATCH net v2 2/2] net: ixgbe: Use new
>PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag
>
>The ixgbe driver use the compile check to determine if it can
>send TLPs to Root Port with the Relaxed Ordering Attribute set,
>this is too inconvenient, now the new flag
>PCI_DEV_FLAGS_NO_RELAXED_ORDERING
>has been added to the kernel and we could check the bit4 in the PCIe
>Device Control register to determine whether we should use the Relaxed
>Ordering Attributes or not, so use this new way in the ixgbe driver.
>
>Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>
>---
> drivers/net/ethernet/intel/ixgbe/ixgbe_82598.c  | 37 ++++++++++++---------
>----
> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c | 32 +++++++++++----------
> 2 files changed, 35 insertions(+), 34 deletions(-)
>
>diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_82598.c
>b/drivers/net/ethernet/intel/ixgbe/ixgbe_82598.c
>index 523f9d0..d1571e3 100644
>--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_82598.c
>+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_82598.c
>@@ -175,31 +175,30 @@ static s32 ixgbe_init_phy_ops_82598(struct ixgbe_hw
>*hw)
>  **/
> static s32 ixgbe_start_hw_82598(struct ixgbe_hw *hw)
> {
>-#ifndef CONFIG_SPARC
>-	u32 regval;
>-	u32 i;
>-#endif
>+	u32 regval, i;
> 	s32 ret_val;
>+	struct ixgbe_adapter *adapter = hw->back;
>
> 	ret_val = ixgbe_start_hw_generic(hw);
>
>-#ifndef CONFIG_SPARC
>-	/* Disable relaxed ordering */
>-	for (i = 0; ((i < hw->mac.max_tx_queues) &&
>-	     (i < IXGBE_DCA_MAX_QUEUES_82598)); i++) {
>-		regval = IXGBE_READ_REG(hw, IXGBE_DCA_TXCTRL(i));
>-		regval &= ~IXGBE_DCA_TXCTRL_DESC_WRO_EN;
>-		IXGBE_WRITE_REG(hw, IXGBE_DCA_TXCTRL(i), regval);
>-	}
>+	if (!pcie_relaxed_ordering_enabled(adapter->pdev)) {

As Alex mentioned there is no need for this check in any form.

The HW defaults to Relaxed Ordering enabled unless it is disabled in 
the PCIe Device Control Register. So the above logic is already done by HW.

All you have to do is strip the code disabling relaxed ordering.

Thanks,
Emil