[Intel-wired-lan] [PATCH 3/9] ixgbevf: use length to determine if descriptor is done

[Singh, Krishneil K]

> -----Original Message-----
> From: Intel-wired-lan [mailto:intel-wired-lan-bounces at osuosl.org] On Behalf Of
> Emil Tantilov
> Sent: Monday, December 11, 2017 10:37 AM
> To: intel-wired-lan at lists.osuosl.org
> Subject: [Intel-wired-lan] [PATCH 3/9] ixgbevf: use length to determine if
> descriptor is done
> 
> Based on:
> commit 7ec0116c9131 ("igb: Use length to determine if descriptor is done")
> 
> This change makes it so that we use the length of the packet instead of the
> DD status bit to determine if a new descriptor is ready to be processed.
> The obvious advantage is that it cuts down on reads as we don't really even
> need the DD bit if going from a 0 to a non-zero value on size is enough to
> inform us that the packet has been completed.
> 
> In addition we only reset the Rx descriptor length for descriptor zero when
> resetting a ring instead of having to do a memset with 0 over the entire
> ring. By doing this we can save some time on initialization.
> 
> Signed-off-by: Emil Tantilov <emil.s.tantilov at intel.com>
> ---
>  drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c |   14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> index 0cc2688..725fe2d 100644
> --- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> +++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> @@ -653,8 +653,8 @@ static void ixgbevf_alloc_rx_buffers(struct ixgbevf_ring
> *rx_ring,
>  			i -= rx_ring->count;
>  		}
> 
> -		/* clear the hdr_addr for the next_to_use descriptor */
> -		rx_desc->read.hdr_addr = 0;
> +		/* clear the length for the next_to_use descriptor */
> +		rx_desc->wb.upper.length = 0;
> 
>  		cleaned_count--;
>  	} while (cleaned_count);
> @@ -938,7 +938,7 @@ static int ixgbevf_clean_rx_irq(struct ixgbevf_q_vector
> *q_vector,
> 
>  		rx_desc = IXGBEVF_RX_DESC(rx_ring, rx_ring->next_to_clean);
> 
> -		if (!ixgbevf_test_staterr(rx_desc, IXGBE_RXD_STAT_DD))
> +		if (!rx_desc->wb.upper.length)
>  			break;
> 
>  		/* This memory barrier is needed to keep us from reading
> @@ -1729,6 +1729,7 @@ static void ixgbevf_configure_rx_ring(struct
> ixgbevf_adapter *adapter,
>  				      struct ixgbevf_ring *ring)
>  {
>  	struct ixgbe_hw *hw = &adapter->hw;
> +	union ixgbe_adv_rx_desc *rx_desc;
>  	u64 rdba = ring->dma;
>  	u32 rxdctl;
>  	u8 reg_idx = ring->reg_idx;
> @@ -1757,6 +1758,10 @@ static void ixgbevf_configure_rx_ring(struct
> ixgbevf_adapter *adapter,
>  	IXGBE_WRITE_REG(hw, IXGBE_VFRDT(reg_idx), 0);
>  	ring->tail = adapter->io_addr + IXGBE_VFRDT(reg_idx);
> 
> +	/* initialize Rx descriptor 0 */
> +	rx_desc = IXGBEVF_RX_DESC(ring, 0);
> +	rx_desc->wb.upper.length = 0;
> +
>  	/* reset ntu and ntc to place SW in sync with hardwdare */
>  	ring->next_to_clean = 0;
>  	ring->next_to_use = 0;
> @@ -2141,9 +2146,6 @@ static void ixgbevf_clean_rx_ring(struct ixgbevf_ring
> *rx_ring)
> 
>  	size = sizeof(struct ixgbevf_rx_buffer) * rx_ring->count;
>  	memset(rx_ring->rx_buffer_info, 0, size);
> -
> -	/* Zero out the descriptor ring */
> -	memset(rx_ring->desc, 0, rx_ring->size);
>  }
> 
>  /**
> 
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Tested-by: Krishneil Singh <krishneil.k.singh at intel.com>