Re: [net-next 6/9] ixgbe: fix X540 Completion timeout

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Hello.

On 11/7/2014 11:57 AM, Jeff Kirsher wrote:

> From: Don Skidmore <donald.c.skidmore@intel.com>

> On topologies including few levels of PCIe switching X540 can run into an
> unexpected completion error.  We get around this by waiting after enabling
> loopback a sufficient amount of time until Tx Data Fetch is sent.  We then
> poll the pending transaction bit to ensure we received the completion.  Only
> then do we go on to clear the buffers.

> Signed-of-by: Don Skidmore <donald.c.skidmore@intel.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

> ---
>   drivers/net/ethernet/intel/ixgbe/ixgbe_common.c | 21 ++++++++++++++++++++-
>   1 file changed, 20 insertions(+), 1 deletion(-)

> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> index b5f484b..e314b53 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
[...]
> @@ -3600,6 +3601,24 @@ void ixgbe_clear_tx_pending(struct ixgbe_hw *hw)
>   	hlreg0 = IXGBE_READ_REG(hw, IXGBE_HLREG0);
>   	IXGBE_WRITE_REG(hw, IXGBE_HLREG0, hlreg0 | IXGBE_HLREG0_LPBK);
>
> +	/* wait for a last completion before clearing buffers */
> +	IXGBE_WRITE_FLUSH(hw);
> +	usleep_range(3000, 6000);
> +
> +	/* Before proceeding, make sure that the PCIe block does not have
> +	 * transactions pending.
> +	 */
> +	poll = ixgbe_pcie_timeout_poll(hw);
> +	for (i = 0; i < poll; i++) {
> +		usleep_range(100, 200);
> +		value = ixgbe_read_pci_cfg_word(hw, IXGBE_PCI_DEVICE_STATUS);
> +		if (ixgbe_removed(hw->hw_addr))
> +			goto out;

    Why not just *break*?

> +		if (!(value & IXGBE_PCI_DEVICE_STATUS_TRANSACTION_PENDING))
> +			goto out;

    Likewise.

> +	}
> +
> +out:
>   	/* initiate cleaning flow for buffers in the PCIe transaction layer */
>   	gcr_ext = IXGBE_READ_REG(hw, IXGBE_GCR_EXT);
>   	IXGBE_WRITE_REG(hw, IXGBE_GCR_EXT,

WBR, Sergei