Date:	Mon, 29 Jul 2013 21:46:15 +0000
From:	"Keller, Jacob E" <jacob.e.keller@...el.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [net-next 11/15] ixgbe: call pcie_get_mimimum_link to check if
 device has enough bandwidth

Hi Bjorn,

Here is the patch I was referring to, I think I see what you mean now...

On Mon, 2013-07-29 at 05:52 -0700, Jeff Kirsher wrote:
> From: Jacob Keller <jacob.e.keller@...el.com>
> 
> This patch uses the new pcie_get_minimum_link function to perform a check to
> ensure that the adapter is hooked into a slot which is capable of providing the
> necessary bandwidth. This check supersedes the original method which only
> checked the current pci device. The new method is capable of determining the
> minimum speed and link of an entire PCI chain.
> 
> Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
> Tested-by: Phil Schmitt <phillip.j.schmitt@...el.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> ---
>  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 130 ++++++++++++++++++++++++--
>  1 file changed, 123 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> index 3aff87e..5ec2b74 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> @@ -195,6 +195,79 @@ static s32 ixgbe_get_parent_bus_info(struct ixgbe_adapter *adapter)
>  	return 0;
>  }
>  
> +/**
> + * ixgbe_check_from_parent - Determine whether PCIe info should come from parent
> + * @hw: hw specific details
> + *
> + * This function is used by probe to determine whether a device's PCI-Express
> + * bandwidth details should be gathered from the parent bus instead of from the
> + * device. Used to ensure that various locations all have the correct device ID
> + * checks.
> + */
> +static inline bool ixgbe_pcie_from_parent(struct ixgbe_hw *hw)
> +{
> +	switch (hw->device_id) {
> +	case IXGBE_DEV_ID_82599_SFP_SF_QP:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static void ixgbe_check_minimum_link(struct ixgbe_adapter *adapter,
> +				     int expected_gts)
> +{
> +	int max_gts = 0;
> +	enum pci_bus_speed speed = PCI_SPEED_UNKNOWN;
> +	enum pcie_link_width width = PCIE_LNK_WIDTH_UNKNOWN;
> +	struct pci_dev *pdev;
> +
> +	/* determine whether to use the the parent device
> +	 */
> +	if (ixgbe_pcie_from_parent(&adapter->hw))
> +		pdev = adapter->pdev->bus->parent->self;
> +	else
> +		pdev = adapter->pdev;
> +
> +	if (pcie_get_minimum_link(pdev, &speed, &width) ||
> +	    speed == PCI_SPEED_UNKNOWN || width == PCIE_LNK_WIDTH_UNKNOWN) {
> +		e_dev_warn("Unable to determine PCI-Express slot throughput.\n");
> +		return;
> +	}
> +
> +	switch (speed) {
> +	case PCIE_SPEED_2_5GT:
> +		/* 8b/10b encoding reduces max throughput */
> +		max_gts = 2 * width;

I use the speed enums here, but I think you're right I don't use the
arrays, those are only used in the pci function directly, and I could
re-spin the patch to remove the addition of those.

Thanks,
Jake

> +		break;
> +	case PCIE_SPEED_5_0GT:
> +		/* 8b/10b encoding reduces max throughput */
> +		max_gts = 4 * width;
> +		break;
> +	case PCIE_SPEED_8_0GT:
> +		/* 128b/130b encoding has less impact on throughput */
> +		max_gts = 8 * width;
> +		break;
> +	default:
> +		e_dev_warn("Unable to determine PCI-Express throughput.\n");
> +		return;
> +	}
> +
> +	if (max_gts < expected_gts) {
> +		e_dev_warn("PCI-Express bandwidth of %dGT/s available (PCI Express:%s:Width x%d)\n",
> +			   max_gts,
> +			   (speed == PCIE_SPEED_8_0GT ? "8.0GT/s" :
> +			    speed == PCIE_SPEED_5_0GT ? "5.0GT/s" :
> +			    speed == PCIE_SPEED_2_5GT ? "2.5GT/s" :
> +			    "Unknown"),
> +			   width);
> +		e_dev_warn("This is not sufficient for optimal performance of this card.\n");
> +		e_dev_warn("For optimal performance, at least %dGT/s of bandwidth is required.\n",
> +			expected_gts);
> +		e_dev_warn("A slot with more lanes and/or higher speed is suggested.\n");
> +	}
> +}
> +
>  static void ixgbe_service_event_schedule(struct ixgbe_adapter *adapter)
>  {
>  	if (!test_bit(__IXGBE_DOWN, &adapter->state) &&
> @@ -7250,6 +7323,41 @@ static const struct net_device_ops ixgbe_netdev_ops = {
>  };
>  
>  /**
> + * ixgbe_enumerate_functions - Get the number of ports this device has
> + * @adapter: adapter structure
> + *
> + * This function enumerates the phsyical functions co-located on a single slot,
> + * in order to determine how many ports a device has. This is most useful in
> + * determining the required GT/s of PCIe bandwidth necessary for optimal
> + * performance.
> + **/
> +static inline int ixgbe_enumerate_functions(struct ixgbe_adapter *adapter)
> +{
> +	struct ixgbe_hw *hw = &adapter->hw;
> +	struct list_head *entry;
> +	int physfns = 0;
> +
> +	/* Some cards can not use the generic count PCIe functions method, and
> +	 * so must be hardcoded to the correct value.
> +	 */
> +	switch (hw->device_id) {
> +	case IXGBE_DEV_ID_82599_SFP_SF_QP:
> +		physfns = 4;
> +		break;
> +	default:
> +		list_for_each(entry, &adapter->pdev->bus_list) {
> +			struct pci_dev *pdev =
> +				list_entry(entry, struct pci_dev, bus_list);
> +			/* don't count virtual functions */
> +			if (!pdev->is_virtfn)
> +				physfns++;
> +		}
> +	}
> +
> +	return physfns;
> +}
> +
> +/**
>   * ixgbe_wol_supported - Check whether device supports WoL
>   * @hw: hw specific details
>   * @device_id: the device ID
> @@ -7331,7 +7439,7 @@ static int ixgbe_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  	struct ixgbe_hw *hw;
>  	const struct ixgbe_info *ii = ixgbe_info_tbl[ent->driver_data];
>  	static int cards_found;
> -	int i, err, pci_using_dac;
> +	int i, err, pci_using_dac, expected_gts;
>  	unsigned int indices = MAX_TX_QUEUES;
>  	u8 part_str[IXGBE_PBANUM_LENGTH];
>  #ifdef IXGBE_FCOE
> @@ -7620,7 +7728,7 @@ skip_sriov:
>  
>  	/* pick up the PCI bus settings for reporting later */
>  	hw->mac.ops.get_bus_info(hw);
> -	if (hw->device_id == IXGBE_DEV_ID_82599_SFP_SF_QP)
> +	if (ixgbe_pcie_from_parent(hw))
>  		ixgbe_get_parent_bus_info(adapter);
>  
>  	/* print bus type/speed/width info */
> @@ -7646,12 +7754,20 @@ skip_sriov:
>  		e_dev_info("MAC: %d, PHY: %d, PBA No: %s\n",
>  			   hw->mac.type, hw->phy.type, part_str);
>  
> -	if (hw->bus.width <= ixgbe_bus_width_pcie_x4) {
> -		e_dev_warn("PCI-Express bandwidth available for this card is "
> -			   "not sufficient for optimal performance.\n");
> -		e_dev_warn("For optimal performance a x8 PCI-Express slot "
> -			   "is required.\n");
> +	/* calculate the expected PCIe bandwidth required for optimal
> +	 * performance. Note that some older parts will never have enough
> +	 * bandwidth due to being older generation PCIe parts. We clamp these
> +	 * parts to ensure no warning is displayed if it can't be fixed.
> +	 */
> +	switch (hw->mac.type) {
> +	case ixgbe_mac_82598EB:
> +		expected_gts = min(ixgbe_enumerate_functions(adapter) * 10, 16);
> +		break;
> +	default:
> +		expected_gts = ixgbe_enumerate_functions(adapter) * 10;
> +		break;
>  	}
> +	ixgbe_check_minimum_link(adapter, expected_gts);
>  
>  	/* reset the hardware with the new settings */
>  	err = hw->mac.ops.start_hw(hw);

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