[net-next,1/7] net: stmmac: set MSS for each tx DMA channel

The DMA engine in dwmac4 can segment a large TSO packet to several
smaller packets of (max) size Maximum Segment Size (MSS).

The DMA engine fetches and saves the MSS via a context descriptor.

This context decriptor has to be provided to each tx DMA channel.
To ensure that this is done, move struct member mss from stmmac_priv
to stmmac_tx_queue.

stmmac_reset_queues_param() now also resets mss, together with other
queue parameters, so reset of mss value can be removed from
stmmac_resume().

init_dma_tx_desc_rings() now also resets mss, together with other
queue parameters, so reset of mss value can be removed from
stmmac_open().

This fixes tx queue timeouts for dwmac4, with DT property
snps,tx-queues-to-use > 1, when running iperf3 with multiple threads.

Fixes: ce736788e8a9 ("net: stmmac: adding multiple buffers for TX")
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac.h      |  2 +-
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 13 +++++--------
 2 files changed, 6 insertions(+), 9 deletions(-)

Hi Niklas

I had a look at this series that looks ok for me.

Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>

On 2/19/2018 6:11 PM, Niklas Cassel wrote:
> The DMA engine in dwmac4 can segment a large TSO packet to several
> smaller packets of (max) size Maximum Segment Size (MSS).
>
> The DMA engine fetches and saves the MSS via a context descriptor.
>
> This context decriptor has to be provided to each tx DMA channel.
> To ensure that this is done, move struct member mss from stmmac_priv
> to stmmac_tx_queue.
>
> stmmac_reset_queues_param() now also resets mss, together with other
> queue parameters, so reset of mss value can be removed from
> stmmac_resume().
>
> init_dma_tx_desc_rings() now also resets mss, together with other
> queue parameters, so reset of mss value can be removed from
> stmmac_open().
>
> This fixes tx queue timeouts for dwmac4, with DT property
> snps,tx-queues-to-use > 1, when running iperf3 with multiple threads.
>
> Fixes: ce736788e8a9 ("net: stmmac: adding multiple buffers for TX")
> Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
> ---
>   drivers/net/ethernet/stmicro/stmmac/stmmac.h      |  2 +-
>   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 13 +++++--------
>   2 files changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> index a916e13624eb..75161e1b7e55 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> @@ -58,6 +58,7 @@ struct stmmac_tx_queue {
>   	unsigned int dirty_tx;
>   	dma_addr_t dma_tx_phy;
>   	u32 tx_tail_addr;
> +	u32 mss;
>   };
>   
>   struct stmmac_rx_queue {
> @@ -138,7 +139,6 @@ struct stmmac_priv {
>   	spinlock_t ptp_lock;
>   	void __iomem *mmcaddr;
>   	void __iomem *ptpaddr;
> -	u32 mss;
>   
>   #ifdef CONFIG_DEBUG_FS
>   	struct dentry *dbgfs_dir;
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 7ad841434ec8..d38bf38f12f5 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1355,6 +1355,7 @@ static int init_dma_tx_desc_rings(struct net_device *dev)
>   
>   		tx_q->dirty_tx = 0;
>   		tx_q->cur_tx = 0;
> +		tx_q->mss = 0;
>   
>   		netdev_tx_reset_queue(netdev_get_tx_queue(priv->dev, queue));
>   	}
> @@ -1946,6 +1947,7 @@ static void stmmac_tx_err(struct stmmac_priv *priv, u32 chan)
>   						     (i == DMA_TX_SIZE - 1));
>   	tx_q->dirty_tx = 0;
>   	tx_q->cur_tx = 0;
> +	tx_q->mss = 0;
>   	netdev_tx_reset_queue(netdev_get_tx_queue(priv->dev, chan));
>   	stmmac_start_tx_dma(priv, chan);
>   
> @@ -2632,7 +2634,6 @@ static int stmmac_open(struct net_device *dev)
>   
>   	priv->dma_buf_sz = STMMAC_ALIGN(buf_sz);
>   	priv->rx_copybreak = STMMAC_RX_COPYBREAK;
> -	priv->mss = 0;
>   
>   	ret = alloc_dma_desc_resources(priv);
>   	if (ret < 0) {
> @@ -2872,10 +2873,10 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
>   	mss = skb_shinfo(skb)->gso_size;
>   
>   	/* set new MSS value if needed */
> -	if (mss != priv->mss) {
> +	if (mss != tx_q->mss) {
>   		mss_desc = tx_q->dma_tx + tx_q->cur_tx;
>   		priv->hw->desc->set_mss(mss_desc, mss);
> -		priv->mss = mss;
> +		tx_q->mss = mss;
>   		tx_q->cur_tx = STMMAC_GET_ENTRY(tx_q->cur_tx, DMA_TX_SIZE);
>   	}
>   
> @@ -4436,6 +4437,7 @@ static void stmmac_reset_queues_param(struct stmmac_priv *priv)
>   
>   		tx_q->cur_tx = 0;
>   		tx_q->dirty_tx = 0;
> +		tx_q->mss = 0;
>   	}
>   }
>   
> @@ -4481,11 +4483,6 @@ int stmmac_resume(struct device *dev)
>   
>   	stmmac_reset_queues_param(priv);
>   
> -	/* reset private mss value to force mss context settings at
> -	 * next tso xmit (only used for gmac4).
> -	 */
> -	priv->mss = 0;
> -
>   	stmmac_clear_descriptors(priv);
>   
>   	stmmac_hw_setup(ndev, false);