Re: [PATCH net-next 1/5] net: mvneta: Use cacheable memory to store the rx buffer virtual address

Jisheng Zhang
2016-11-28T08:41:14Z

Hi Gregory,

On Fri, 25 Nov 2016 16:30:14 +0100 Gregory CLEMENT wrote:

> Until now the virtual address of the received buffer were stored in the
> cookie field of the rx descriptor. However, this field is 32-bits only
> which prevents to use the driver on a 64-bits architecture.
>
> With this patch the virtual address is stored in an array not shared with
> the hardware (no more need to use the DMA API). Thanks to this, it is
> possible to use cache contrary to the access of the rx descriptor member.
>
> The change is done in the swbm path only because the hwbm uses the cookie
> field, this also means that currently the hwbm is not usable in 64-bits.
>
> Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
> ---
> drivers/net/ethernet/marvell/mvneta.c | 96 ++++++++++++++++++++++++----
> 1 file changed, 84 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 87274d4ab102..b6849f88cab7 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -561,6 +561,9 @@ struct mvneta_rx_queue {
> u32 pkts_coal;
> u32 time_coal;
>
> + /* Virtual address of the RX buffer */
> + void **buf_virt_addr;

can we store buf_phys_addr in cacheable memory as well?

> +
> /* Virtual address of the RX DMA descriptors array */
> struct mvneta_rx_desc *descs;
>
> @@ -1573,10 +1576,14 @@ static void mvneta_tx_done_pkts_coal_set(struct mvneta_port *pp,
>
> /* Handle rx descriptor fill by setting buf_cookie and buf_phys_addr */
> static void mvneta_rx_desc_fill(struct mvneta_rx_desc *rx_desc,
> - u32 phys_addr, u32 cookie)
> + u32 phys_addr, void *virt_addr,
> + struct mvneta_rx_queue *rxq)
> {
> - rx_desc->buf_cookie = cookie;
> + int i;
> +
> rx_desc->buf_phys_addr = phys_addr;
> + i = rx_desc - rxq->descs;
> + rxq->buf_virt_addr[i] = virt_addr;
> }
>
> /* Decrement sent descriptors counter */
> @@ -1781,7 +1788,8 @@ EXPORT_SYMBOL_GPL(mvneta_frag_free);
>
> /* Refill processing for SW buffer management */
> static int mvneta_rx_refill(struct mvneta_port *pp,
> - struct mvneta_rx_desc *rx_desc)
> + struct mvneta_rx_desc *rx_desc,
> + struct mvneta_rx_queue *rxq)
>
> {
> dma_addr_t phys_addr;
> @@ -1799,7 +1807,7 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
> return -ENOMEM;
> }
>
> - mvneta_rx_desc_fill(rx_desc, phys_addr, (u32)data);
> + mvneta_rx_desc_fill(rx_desc, phys_addr, data, rxq);
> return 0;
> }
>
> @@ -1861,7 +1869,12 @@ static void mvneta_rxq_drop_pkts(struct mvneta_port *pp,
>
> for (i = 0; i < rxq->size; i++) {
> struct mvneta_rx_desc *rx_desc = rxq->descs + i;
> - void *data = (void *)rx_desc->buf_cookie;
> + void *data;
> +
> + if (!pp->bm_priv)
> + data = rxq->buf_virt_addr[i];
> + else
> + data = (void *)(uintptr_t)rx_desc->buf_cookie;
>
> dma_unmap_single(pp->dev->dev.parent, rx_desc->buf_phys_addr,
> MVNETA_RX_BUF_SIZE(pp->pkt_size), DMA_FROM_DEVICE);
> @@ -1894,12 +1907,13 @@ static int mvneta_rx_swbm(struct mvneta_port *pp, int rx_todo,
> unsigned char *data;
> dma_addr_t phys_addr;
> u32 rx_status, frag_size;
> - int rx_bytes, err;
> + int rx_bytes, err, index;
>
> rx_done++;
> rx_status = rx_desc->status;
> rx_bytes = rx_desc->data_size - (ETH_FCS_LEN + MVNETA_MH_SIZE);
> - data = (unsigned char *)rx_desc->buf_cookie;
> + index = rx_desc - rxq->descs;
> + data = (unsigned char *)rxq->buf_virt_addr[index];
> phys_addr = rx_desc->buf_phys_addr;
>
> if (!mvneta_rxq_desc_is_first_last(rx_status) ||
> @@ -1938,7 +1952,7 @@ static int mvneta_rx_swbm(struct mvneta_port *pp, int rx_todo,
> }
>
> /* Refill processing */
> - err = mvneta_rx_refill(pp, rx_desc);
> + err = mvneta_rx_refill(pp, rx_desc, rxq);
> if (err) {
> netdev_err(dev, "Linux processing - Can't refill\n");
> rxq->missed++;
> @@ -2020,7 +2034,7 @@ static int mvneta_rx_hwbm(struct mvneta_port *pp, int rx_todo,
> rx_done++;
> rx_status = rx_desc->status;
> rx_bytes = rx_desc->data_size - (ETH_FCS_LEN + MVNETA_MH_SIZE);
> - data = (unsigned char *)rx_desc->buf_cookie;
> + data = (u8 *)(uintptr_t)rx_desc->buf_cookie;
> phys_addr = rx_desc->buf_phys_addr;
> pool_id = MVNETA_RX_GET_BM_POOL_ID(rx_desc);
> bm_pool = &pp->bm_priv->bm_pools[pool_id];
> @@ -2708,6 +2722,57 @@ static int mvneta_poll(struct napi_struct *napi, int budget)
> return rx_done;
> }
>
> +/* Refill processing for HW buffer management */
> +static int mvneta_rx_hwbm_refill(struct mvneta_port *pp,
> + struct mvneta_rx_desc *rx_desc)
> +
> +{
> + dma_addr_t phys_addr;
> + void *data;
> +
> + data = mvneta_frag_alloc(pp->frag_size);
> + if (!data)
> + return -ENOMEM;
> +
> + phys_addr = dma_map_single(pp->dev->dev.parent, data,
> + MVNETA_RX_BUF_SIZE(pp->pkt_size),
> + DMA_FROM_DEVICE);
> + if (unlikely(dma_mapping_error(pp->dev->dev.parent, phys_addr))) {
> + mvneta_frag_free(pp->frag_size, data);
> + return -ENOMEM;
> + }
> +
> + phys_addr += pp->rx_offset_correction;
> + rx_desc->buf_phys_addr = phys_addr;
> + rx_desc->buf_cookie = (uintptr_t)data;
> +
> + return 0;
> +}
> +
> +/* Handle rxq fill: allocates rxq skbs; called when initializing a port */
> +static int mvneta_rxq_bm_fill(struct mvneta_port *pp,
> + struct mvneta_rx_queue *rxq,
> + int num)
> +{
> + int i;
> +
> + for (i = 0; i < num; i++) {
> + memset(rxq->descs + i, 0, sizeof(struct mvneta_rx_desc));
> + if (mvneta_rx_hwbm_refill(pp, rxq->descs + i) != 0) {
> + netdev_err(pp->dev, "%s:rxq %d, %d of %d buffs filled\n",
> + __func__, rxq->id, i, num);
> + break;
> + }
> + }
> +
> + /* Add this number of RX descriptors as non occupied (ready to
> + * get packets)
> + */
> + mvneta_rxq_non_occup_desc_add(pp, rxq, i);
> +
> + return i;
> +}
> +
> /* Handle rxq fill: allocates rxq skbs; called when initializing a port */
> static int mvneta_rxq_fill(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
> int num)
> @@ -2716,7 +2781,7 @@ static int mvneta_rxq_fill(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
>
> for (i = 0; i < num; i++) {
> memset(rxq->descs + i, 0, sizeof(struct mvneta_rx_desc));
> - if (mvneta_rx_refill(pp, rxq->descs + i) != 0) {
> + if (mvneta_rx_refill(pp, rxq->descs + i, rxq) != 0) {
> netdev_err(pp->dev, "%s:rxq %d, %d of %d buffs filled\n",
> __func__, rxq->id, i, num);
> break;
> @@ -2784,14 +2849,21 @@ static int mvneta_rxq_init(struct mvneta_port *pp,
> mvneta_rxq_buf_size_set(pp, rxq,
> MVNETA_RX_BUF_SIZE(pp->pkt_size));
> mvneta_rxq_bm_disable(pp, rxq);
> +
> + rxq->buf_virt_addr = devm_kmalloc(pp->dev->dev.parent,
> + rxq->size * sizeof(void *),
> + GFP_KERNEL);

I would suggest allocate this buffer during probe. Otherwise, there's
memory leak if we either change the mtu or close then open the eth in
a loop, e.g

while true
do
ifconfig eth0 up
ifconfig eth0 down
done

Thanks,
Jisheng

> + if (!rxq->buf_virt_addr)
> + return -ENOMEM;
> +
> + mvneta_rxq_fill(pp, rxq, rxq->size);
> } else {
> mvneta_rxq_bm_enable(pp, rxq);
> mvneta_rxq_long_pool_set(pp, rxq);
> mvneta_rxq_short_pool_set(pp, rxq);
> + mvneta_rxq_bm_fill(pp, rxq, rxq->size);
> }
>
> - mvneta_rxq_fill(pp, rxq, rxq->size);
> -
> return 0;
> }
>