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SubjectRE: [PATCH 05/14] net: axienet: Factor out TX descriptor chain cleanup
Date
> -----Original Message-----
> From: Andre Przywara <andre.przywara@arm.com>
> Sent: Friday, January 10, 2020 5:24 PM
> To: David S . Miller <davem@davemloft.net>; Radhey Shyam Pandey
> <radheys@xilinx.com>
> Cc: Michal Simek <michals@xilinx.com>; Robert Hancock
> <hancock@sedsystems.ca>; netdev@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; linux-kernel@vger.kernel.org
> Subject: [PATCH 05/14] net: axienet: Factor out TX descriptor chain cleanup
>
> Factor out the code that cleans up a number of connected TX descriptors,
> as we will need it to properly roll back a failed _xmit() call.
> There are subtle differences between cleaning up a successfully sent
> chain (unknown number of involved descriptors, total data size needed)
> and a chain that was about to set up (number of descriptors known), so
> cater for those variations with some extra parameters.
>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
> .../net/ethernet/xilinx/xilinx_axienet_main.c | 75 ++++++++++++-------
> 1 file changed, 50 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> index ec5d01adc1d5..82abe2b0f16a 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> @@ -543,33 +543,37 @@ static int axienet_device_reset(struct net_device
> *ndev)
> return 0;
> }
>
> -/**
> - * axienet_start_xmit_done - Invoked once a transmit is completed by the
> - * Axi DMA Tx channel.
> - * @ndev: Pointer to the net_device structure
> - *
> - * This function is invoked from the Axi DMA Tx isr to notify the completion
> - * of transmit operation. It clears fields in the corresponding Tx BDs and
> - * unmaps the corresponding buffer so that CPU can regain ownership of
> the
> - * buffer. It finally invokes "netif_wake_queue" to restart transmission if
> - * required.
> +/* Clean up a series of linked TX descriptors. Would either be called
> + * after a successful transmit operation, or after there was an error
> + * when setting up the chain.
> + * Returns the number of descriptors handled.
> */
> -static void axienet_start_xmit_done(struct net_device *ndev)

To be consistent we can add the doxygen function description.
The rest looks good. Feel free to add:
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>

> +static int axienet_free_tx_chain(struct net_device *ndev, u32 first_bd,
> + int nr_bds, u32 *sizep)
> {
> - u32 size = 0;
> - u32 packets = 0;
> struct axienet_local *lp = netdev_priv(ndev);
> + int max_bds = (nr_bds != -1) ? nr_bds : lp->tx_bd_num;
> struct axidma_bd *cur_p;
> - unsigned int status = 0;
> + unsigned int status;
> + int i;
> +
> + for (i = 0; i < max_bds; i++) {
> + cur_p = &lp->tx_bd_v[(first_bd + i) % lp->tx_bd_num];
> + status = cur_p->status;
> +
> + /* If no number is given, clean up *all* descriptors that have
> + * been completed by the MAC.
> + */
> + if (nr_bds == -1 && !(status &
> XAXIDMA_BD_STS_COMPLETE_MASK))
> + break;
>
> - cur_p = &lp->tx_bd_v[lp->tx_bd_ci];
> - status = cur_p->status;
> - while (status & XAXIDMA_BD_STS_COMPLETE_MASK) {
> dma_unmap_single(ndev->dev.parent, cur_p->phys,
> (cur_p->cntrl &
> XAXIDMA_BD_CTRL_LENGTH_MASK),
> DMA_TO_DEVICE);
> - if (cur_p->skb)
> +
> + if (cur_p->skb && (status &
> XAXIDMA_BD_STS_COMPLETE_MASK))
> dev_consume_skb_irq(cur_p->skb);
> +
> cur_p->cntrl = 0;
> cur_p->app0 = 0;
> cur_p->app1 = 0;
> @@ -578,15 +582,36 @@ static void axienet_start_xmit_done(struct
> net_device *ndev)
> cur_p->status = 0;
> cur_p->skb = NULL;
>
> - size += status & XAXIDMA_BD_STS_ACTUAL_LEN_MASK;
> - packets++;
> -
> - if (++lp->tx_bd_ci >= lp->tx_bd_num)
> - lp->tx_bd_ci = 0;
> - cur_p = &lp->tx_bd_v[lp->tx_bd_ci];
> - status = cur_p->status;
> + if (sizep)
> + *sizep += status &
> XAXIDMA_BD_STS_ACTUAL_LEN_MASK;
> }
>
> + return i;
> +}
> +
> +/**
> + * axienet_start_xmit_done - Invoked once a transmit is completed by the
> + * Axi DMA Tx channel.
> + * @ndev: Pointer to the net_device structure
> + *
> + * This function is invoked from the Axi DMA Tx isr to notify the completion
> + * of transmit operation. It clears fields in the corresponding Tx BDs and
> + * unmaps the corresponding buffer so that CPU can regain ownership of
> the
> + * buffer. It finally invokes "netif_wake_queue" to restart transmission if
> + * required.
> + */
> +static void axienet_start_xmit_done(struct net_device *ndev)
> +{
> + u32 size = 0;
> + u32 packets = 0;
> + struct axienet_local *lp = netdev_priv(ndev);
> +
> + packets = axienet_free_tx_chain(ndev, lp->tx_bd_ci, -1, &size);
> +
> + lp->tx_bd_ci += packets;
> + if (lp->tx_bd_ci >= lp->tx_bd_num)
> + lp->tx_bd_ci -= lp->tx_bd_num;
> +
> ndev->stats.tx_packets += packets;
> ndev->stats.tx_bytes += size;
>
> --
> 2.17.1

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