[PATCH RFC 05/11] dpaa_eth: add support for S/G frames

From: Madalin Bucur
Date: Tue Mar 17 2015 - 14:59:00 EST

Add support for Scater/Gather (S/G) frames. The FMan can place
the frame content into multiple buffers and provide a S/G Table
(SGT) into one first buffer with references to the others.

Signed-off-by: Madalin Bucur <madalin.bucur@xxxxxxxxxxxxx>
---
drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 6 +
.../net/ethernet/freescale/dpaa/dpaa_eth_common.c | 34 +-
.../net/ethernet/freescale/dpaa/dpaa_eth_common.h | 2 +
drivers/net/ethernet/freescale/dpaa/dpaa_eth_sg.c | 356 +++++++++++++++++++--
4 files changed, 367 insertions(+), 31 deletions(-)

diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index efa9711..ebd50f3 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
@@ -574,6 +574,12 @@ static int dpa_private_netdev_init(struct net_device *net_dev)
net_dev->hw_features |= (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
NETIF_F_LLTX);

+ /* Advertise S/G and HIGHDMA support for private interfaces */
+ net_dev->hw_features |= NETIF_F_SG | NETIF_F_HIGHDMA;
+ /* Recent kernels enable GSO automatically, if
+ * we declare NETIF_F_SG. For conformity, we'll
+ * still declare GSO explicitly.
+ */
net_dev->features |= NETIF_F_GSO;

return dpa_netdev_init(net_dev, mac_addr, tx_timeout);
diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth_common.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth_common.c
index 7094a45..1fdb35d 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth_common.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth_common.c
@@ -1162,9 +1162,38 @@ void dpaa_eth_init_ports(struct mac_device *mac_dev,
}
EXPORT_SYMBOL(dpaa_eth_init_ports);

+void dpa_release_sgt(struct qm_sg_entry *sgt)
+{
+ struct dpa_bp *dpa_bp;
+ struct bm_buffer bmb[DPA_BUFF_RELEASE_MAX];
+ u8 i = 0, j;
+
+ do {
+ dpa_bp = dpa_bpid2pool(sgt[i].bpid);
+ DPA_ERR_ON(!dpa_bp);
+
+ j = 0;
+ do {
+ DPA_ERR_ON(sgt[i].extension);
+
+ bmb[j].hi = sgt[i].addr_hi;
+ bmb[j].lo = sgt[i].addr_lo;
+
+ j++; i++;
+ } while (j < ARRAY_SIZE(bmb) &&
+ !sgt[i - 1].final &&
+ sgt[i - 1].bpid == sgt[i].bpid);
+
+ while (bman_release(dpa_bp->pool, bmb, j, 0))
+ cpu_relax();
+ } while (!sgt[i - 1].final);
+}
+EXPORT_SYMBOL(dpa_release_sgt);
+
void __attribute__((nonnull))
dpa_fd_release(const struct net_device *net_dev, const struct qm_fd *fd)
{
+ struct qm_sg_entry *sgt;
struct dpa_bp *_dpa_bp;
struct bm_buffer _bmb;

@@ -1174,7 +1203,10 @@ dpa_fd_release(const struct net_device *net_dev, const struct qm_fd *fd)
_dpa_bp = dpa_bpid2pool(fd->bpid);
DPA_ERR_ON(!_dpa_bp);

- DPA_ERR_ON(fd->format == qm_fd_sg);
+ if (fd->format == qm_fd_sg) {
+ sgt = (phys_to_virt(bm_buf_addr(&_bmb)) + dpa_fd_offset(fd));
+ dpa_release_sgt(sgt);
+ }

while (bman_release(_dpa_bp->pool, &_bmb, 1, 0))
cpu_relax();
diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth_common.h b/drivers/net/ethernet/freescale/dpaa/dpaa_eth_common.h
index 96bc63e..9b1774e 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth_common.h
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth_common.h
@@ -52,6 +52,7 @@
fm_set_##type##_port_params(port, &param); \
}

+#define DPA_SGT_MAX_ENTRIES 16 /* maximum number of entries in SG Table */
#define DPA_BUFF_RELEASE_MAX 8 /* maximum number of buffers released at once */

/* used in napi related functions */
@@ -110,6 +111,7 @@ void dpaa_eth_init_ports(struct mac_device *mac_dev,
struct fm_port_fqs *port_fqs,
struct dpa_buffer_layout_s *buf_layout,
struct device *dev);
+void dpa_release_sgt(struct qm_sg_entry *sgt);
void __attribute__((nonnull))
dpa_fd_release(const struct net_device *net_dev, const struct qm_fd *fd);
int dpa_enable_tx_csum(struct dpa_priv_s *priv,
diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth_sg.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth_sg.c
index 1b3dc28..410effd 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth_sg.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth_sg.c
@@ -54,6 +54,31 @@
skb = *(skbh + (off)); \
}

+/* DMA map and add a page frag back into the bpool.
+ * @vaddr fragment must have been allocated with netdev_alloc_frag(),
+ * specifically for fitting into @dpa_bp.
+ */
+static void dpa_bp_recycle_frag(struct dpa_bp *dpa_bp, unsigned long vaddr,
+ int *count_ptr)
+{
+ struct bm_buffer bmb;
+ dma_addr_t addr;
+
+ addr = dma_map_single(dpa_bp->dev, (void *)vaddr, dpa_bp->size,
+ DMA_BIDIRECTIONAL);
+ if (unlikely(dma_mapping_error(dpa_bp->dev, addr))) {
+ dev_err(dpa_bp->dev, "DMA mapping failed");
+ return;
+ }
+
+ bm_buffer_set64(&bmb, addr);
+
+ while (bman_release(dpa_bp->pool, &bmb, 1, 0))
+ cpu_relax();
+
+ (*count_ptr)++;
+}
+
static int _dpa_bp_add_8_bufs(const struct dpa_bp *dpa_bp)
{
struct bm_buffer bmb[8];
@@ -188,6 +213,8 @@ EXPORT_SYMBOL(dpaa_eth_refill_bpools);
struct sk_buff *_dpa_cleanup_tx_fd(const struct dpa_priv_s *priv,
const struct qm_fd *fd)
{
+ const struct qm_sg_entry *sgt;
+ int i;
struct dpa_bp *dpa_bp = priv->dpa_bp;
dma_addr_t addr = qm_fd_addr(fd);
struct sk_buff **skbh;
@@ -201,6 +228,28 @@ struct sk_buff *_dpa_cleanup_tx_fd(const struct dpa_priv_s *priv,
DPA_READ_SKB_PTR(skb, skbh, phys_to_virt(addr), 0);
nr_frags = skb_shinfo(skb)->nr_frags;

+ if (fd->format == qm_fd_sg) {
+ /* The sgt buffer has been allocated with netdev_alloc_frag(),
+ * it's from lowmem.
+ */
+ sgt = phys_to_virt(addr + dpa_fd_offset(fd));
+
+ /* sgt[0] is from lowmem, was dma_map_single()-ed */
+ dma_unmap_single(dpa_bp->dev, (dma_addr_t)sgt[0].addr,
+ sgt[0].length, dma_dir);
+
+ /* remaining pages were mapped with dma_map_page() */
+ for (i = 1; i < nr_frags; i++) {
+ DPA_ERR_ON(sgt[i].extension);
+
+ dma_unmap_page(dpa_bp->dev, (dma_addr_t)sgt[i].addr,
+ sgt[i].length, dma_dir);
+ }
+
+ /* Free the page frag that we allocated on Tx */
+ put_page(virt_to_head_page(sgt));
+ }
+
return skb;
}

@@ -234,6 +283,107 @@ static struct sk_buff *__hot contig_fd_to_skb(const struct dpa_priv_s *priv,
return skb;
}

+/* Build an skb with the data of the first S/G entry in the linear portion and
+ * the rest of the frame as skb fragments.
+ *
+ * The page fragment holding the S/G Table is recycled here.
+ */
+static struct sk_buff *__hot sg_fd_to_skb(const struct dpa_priv_s *priv,
+ const struct qm_fd *fd,
+ int *count_ptr)
+{
+ const struct qm_sg_entry *sgt;
+ dma_addr_t addr = qm_fd_addr(fd);
+ ssize_t fd_off = dpa_fd_offset(fd);
+ dma_addr_t sg_addr;
+ void *vaddr, *sg_vaddr;
+ struct dpa_bp *dpa_bp;
+ struct page *page, *head_page;
+ int frag_offset, frag_len;
+ int page_offset;
+ int i;
+ struct sk_buff *skb = NULL, *skb_tmp, **skbh;
+
+ vaddr = phys_to_virt(addr);
+ DPA_ERR_ON(!IS_ALIGNED((unsigned long)vaddr, SMP_CACHE_BYTES));
+
+ dpa_bp = priv->dpa_bp;
+ /* Iterate through the SGT entries and add data buffers to the skb */
+ sgt = vaddr + fd_off;
+ for (i = 0; i < DPA_SGT_MAX_ENTRIES; i++) {
+ /* Extension bit is not supported */
+ DPA_ERR_ON(sgt[i].extension);
+
+ /* We use a single global Rx pool */
+ DPA_ERR_ON(dpa_bp != dpa_bpid2pool(sgt[i].bpid));
+
+ sg_addr = qm_sg_addr(&sgt[i]);
+ sg_vaddr = phys_to_virt(sg_addr);
+ DPA_ERR_ON(!IS_ALIGNED((unsigned long)sg_vaddr,
+ SMP_CACHE_BYTES));
+
+ dma_unmap_single(dpa_bp->dev, sg_addr, dpa_bp->size,
+ DMA_BIDIRECTIONAL);
+ if (i == 0) {
+ DPA_READ_SKB_PTR(skb, skbh, sg_vaddr, -1);
+ DPA_ERR_ON(skb->head != sg_vaddr);
+
+ skb->ip_summed = CHECKSUM_NONE;
+
+ /* Make sure forwarded skbs will have enough space
+ * on Tx, if extra headers are added.
+ */
+ DPA_ERR_ON(fd_off != priv->rx_headroom);
+ skb_reserve(skb, fd_off);
+ skb_put(skb, sgt[i].length);
+ } else {
+ /* Not the first S/G entry; all data from buffer will
+ * be added in an skb fragment; fragment index is offset
+ * by one since first S/G entry was incorporated in the
+ * linear part of the skb.
+ *
+ * Caution: 'page' may be a tail page.
+ */
+ DPA_READ_SKB_PTR(skb_tmp, skbh, sg_vaddr, -1);
+ page = virt_to_page(sg_vaddr);
+ head_page = virt_to_head_page(sg_vaddr);
+
+ /* Free (only) the skbuff shell because its data buffer
+ * is already a frag in the main skb.
+ */
+ get_page(head_page);
+ dev_kfree_skb(skb_tmp);
+
+ /* Compute offset in (possibly tail) page */
+ page_offset = ((unsigned long)sg_vaddr &
+ (PAGE_SIZE - 1)) +
+ (page_address(page) - page_address(head_page));
+ /* page_offset only refers to the beginning of sgt[i];
+ * but the buffer itself may have an internal offset.
+ */
+ frag_offset = sgt[i].offset + page_offset;
+ frag_len = sgt[i].length;
+ /* skb_add_rx_frag() does no checking on the page; if
+ * we pass it a tail page, we'll end up with
+ * bad page accounting and eventually with segafults.
+ */
+ skb_add_rx_frag(skb, i - 1, head_page, frag_offset,
+ frag_len, dpa_bp->size);
+ }
+ /* Update the pool count for the current {cpu x bpool} */
+ (*count_ptr)--;
+
+ if (sgt[i].final)
+ break;
+ }
+ WARN_ONCE(i == DPA_SGT_MAX_ENTRIES, "No final bit on SGT\n");
+
+ /* recycle the SGT fragment */
+ DPA_ERR_ON(dpa_bp != dpa_bpid2pool(fd->bpid));
+ dpa_bp_recycle_frag(dpa_bp, (unsigned long)vaddr, count_ptr);
+ return skb;
+}
+
void __hot _dpa_rx(struct net_device *net_dev,
struct qman_portal *portal,
const struct dpa_priv_s *priv,
@@ -261,17 +411,20 @@ void __hot _dpa_rx(struct net_device *net_dev,
dpa_bp = priv->dpa_bp;
DPA_ERR_ON(dpa_bp != dpa_bpid2pool(fd->bpid));

- /* prefetch the first 64 bytes of the frame */
+ /* prefetch the first 64 bytes of the frame or the SGT start */
dma_unmap_single(dpa_bp->dev, addr, dpa_bp->size, DMA_BIDIRECTIONAL);
prefetch(phys_to_virt(addr) + dpa_fd_offset(fd));

- /* The only FD type that we may receive is contig */
- DPA_ERR_ON((fd->format != qm_fd_contig));
+ /* The only FD types that we may receive are contig and S/G */
+ DPA_ERR_ON((fd->format != qm_fd_contig) && (fd->format != qm_fd_sg));

- skb = contig_fd_to_skb(priv, fd);
+ if (likely(fd->format == qm_fd_contig))
+ skb = contig_fd_to_skb(priv, fd);
+ else
+ skb = sg_fd_to_skb(priv, fd, count_ptr);

- /* Account for the contig buffer
- * having been removed from the pool.
+ /* Account for either the contig buffer or the SGT buffer (depending on
+ * which case we were in) having been removed from the pool.
*/
(*count_ptr)--;
skb->protocol = eth_type_trans(skb, net_dev);
@@ -358,13 +511,132 @@ static int __hot skb_to_contig_fd(struct dpa_priv_s *priv,
return 0;
}

+static int __hot skb_to_sg_fd(struct dpa_priv_s *priv,
+ struct sk_buff *skb, struct qm_fd *fd)
+{
+ struct dpa_bp *dpa_bp = priv->dpa_bp;
+ dma_addr_t addr;
+ struct sk_buff **skbh;
+ struct net_device *net_dev = priv->net_dev;
+ int err;
+
+ struct qm_sg_entry *sgt;
+ void *sgt_buf;
+ void *buffer_start;
+ skb_frag_t *frag;
+ int i, j;
+ const enum dma_data_direction dma_dir = DMA_TO_DEVICE;
+ const int nr_frags = skb_shinfo(skb)->nr_frags;
+
+ fd->format = qm_fd_sg;
+
+ /* get a page frag to store the SGTable */
+ sgt_buf = netdev_alloc_frag(priv->tx_headroom +
+ sizeof(struct qm_sg_entry) * (1 + nr_frags));
+ if (unlikely(!sgt_buf)) {
+ dev_err(dpa_bp->dev, "netdev_alloc_frag() failed\n");
+ return -ENOMEM;
+ }
+
+ /* Enable L3/L4 hardware checksum computation.
+ *
+ * We must do this before dma_map_single(DMA_TO_DEVICE), because we may
+ * need to write into the skb.
+ */
+ err = dpa_enable_tx_csum(priv, skb, fd,
+ sgt_buf + DPA_TX_PRIV_DATA_SIZE);
+ if (unlikely(err < 0)) {
+ if (netif_msg_tx_err(priv) && net_ratelimit())
+ netdev_err(net_dev, "HW csum error: %d\n", err);
+ goto csum_failed;
+ }
+
+ sgt = (struct qm_sg_entry *)(sgt_buf + priv->tx_headroom);
+ sgt[0].bpid = 0xff;
+ sgt[0].offset = 0;
+ sgt[0].length = skb_headlen(skb);
+ sgt[0].extension = 0;
+ sgt[0].final = 0;
+ addr = dma_map_single(dpa_bp->dev, skb->data, sgt[0].length, dma_dir);
+ if (unlikely(dma_mapping_error(dpa_bp->dev, addr))) {
+ dev_err(dpa_bp->dev, "DMA mapping failed");
+ err = -EINVAL;
+ goto sg0_map_failed;
+ }
+ sgt[0].addr_hi = (u8)upper_32_bits(addr);
+ sgt[0].addr_lo = lower_32_bits(addr);
+
+ /* populate the rest of SGT entries */
+ for (i = 1; i <= nr_frags; i++) {
+ frag = &skb_shinfo(skb)->frags[i - 1];
+ sgt[i].bpid = 0xff;
+ sgt[i].offset = 0;
+ sgt[i].length = frag->size;
+ sgt[i].extension = 0;
+ sgt[i].final = 0;
+
+ DPA_ERR_ON(!skb_frag_page(frag));
+ addr = skb_frag_dma_map(dpa_bp->dev, frag, 0, sgt[i].length,
+ dma_dir);
+ if (unlikely(dma_mapping_error(dpa_bp->dev, addr))) {
+ dev_err(dpa_bp->dev, "DMA mapping failed");
+ err = -EINVAL;
+ goto sg_map_failed;
+ }
+
+ /* keep the offset in the address */
+ sgt[i].addr_hi = (u8)upper_32_bits(addr);
+ sgt[i].addr_lo = lower_32_bits(addr);
+ }
+ sgt[i - 1].final = 1;
+
+ fd->length20 = skb->len;
+ fd->offset = priv->tx_headroom;
+
+ /* DMA map the SGT page */
+ buffer_start = (void *)sgt - dpa_fd_offset(fd);
+ /* Can't write at "negative" offset in buffer_start, because this skb
+ * may not have been allocated by us.
+ */
+ DPA_WRITE_SKB_PTR(skb, skbh, buffer_start, 0);
+
+ addr = dma_map_single(dpa_bp->dev, buffer_start,
+ skb_end_pointer(skb) -
+ (unsigned char *)buffer_start, dma_dir);
+ if (unlikely(dma_mapping_error(dpa_bp->dev, addr))) {
+ dev_err(dpa_bp->dev, "DMA mapping failed");
+ err = -EINVAL;
+ goto sgt_map_failed;
+ }
+
+ fd->bpid = 0xff;
+ fd->cmd |= FM_FD_CMD_FCO;
+ fd->addr_hi = (u8)upper_32_bits(addr);
+ fd->addr_lo = lower_32_bits(addr);
+
+ return 0;
+
+sgt_map_failed:
+sg_map_failed:
+ for (j = 0; j < i; j++)
+ dma_unmap_page(dpa_bp->dev, qm_sg_addr(&sgt[j]),
+ sgt[j].length, dma_dir);
+sg0_map_failed:
+csum_failed:
+ put_page(virt_to_head_page(sgt_buf));
+
+ return err;
+}
+
int __hot dpa_tx(struct sk_buff *skb, struct net_device *net_dev)
{
struct dpa_priv_s *priv;
struct qm_fd fd;
struct dpa_percpu_priv_s *percpu_priv;
struct rtnl_link_stats64 *percpu_stats;
+ int err = 0;
const int queue_mapping = dpa_get_queue_mapping(skb);
+ const bool nonlinear = skb_is_nonlinear(skb);
int *countptr, offset = 0;

priv = netdev_priv(net_dev);
@@ -375,38 +647,60 @@ int __hot dpa_tx(struct sk_buff *skb, struct net_device *net_dev)

clear_fd(&fd);

- /* Make sure we have enough headroom to accommodate private
- * data, parse results, etc. Normally this shouldn't happen if
- * we're here via the standard kernel stack.
+ /* MAX_SKB_FRAGS is larger than our DPA_SGT_MAX_ENTRIES; make sure
+ * we don't feed FMan with more fragments than it supports.
+ * Btw, we're using the first sgt entry to store the linear part of
+ * the skb, so we're one extra frag short.
*/
- if (unlikely(skb_headroom(skb) < priv->tx_headroom)) {
- struct sk_buff *skb_new;
-
- skb_new = skb_realloc_headroom(skb, priv->tx_headroom);
- if (unlikely(!skb_new)) {
+ if (nonlinear &&
+ likely(skb_shinfo(skb)->nr_frags < DPA_SGT_MAX_ENTRIES)) {
+ /* Just create a S/G fd based on the skb */
+ err = skb_to_sg_fd(priv, skb, &fd);
+ } else {
+ /* Make sure we have enough headroom to accommodate private
+ * data, parse results, etc. Normally this shouldn't happen if
+ * we're here via the standard kernel stack.
+ */
+ if (unlikely(skb_headroom(skb) < priv->tx_headroom)) {
+ struct sk_buff *skb_new;
+
+ skb_new = skb_realloc_headroom(skb, priv->tx_headroom);
+ if (unlikely(!skb_new)) {
+ dev_kfree_skb(skb);
+ percpu_stats->tx_errors++;
+ return NETDEV_TX_OK;
+ }
dev_kfree_skb(skb);
- percpu_stats->tx_errors++;
- return NETDEV_TX_OK;
+ skb = skb_new;
}
- dev_kfree_skb(skb);
- skb = skb_new;
- }

- /* We're going to store the skb backpointer at the beginning
- * of the data buffer, so we need a privately owned skb
- */
+ /* We're going to store the skb backpointer at the beginning
+ * of the data buffer, so we need a privately owned skb
+ */

- /* Code borrowed from skb_unshare(). */
- if (skb_cloned(skb)) {
- struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
+ /* Code borrowed from skb_unshare(). */
+ if (skb_cloned(skb)) {
+ struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
+
+ kfree_skb(skb);
+ skb = nskb;
+ /* skb_copy() has now linearized the skbuff. */
+ } else if (unlikely(nonlinear)) {
+ /* We are here because the egress skb contains
+ * more fragments than we support. In this case,
+ * we have no choice but to linearize it ourselves.
+ */
+ err = __skb_linearize(skb);
+ }
+ if (unlikely(!skb || err < 0))
+ /* Common out-of-memory error path */
+ goto enomem;

/* Finally, create a contig FD from this skb */
- skb_to_contig_fd(priv, skb, &fd, countptr, &offset);
-
- kfree_skb(skb);
- skb = nskb;
- /* skb_copy() has now linearized the skbuff. */
+ err = skb_to_contig_fd(priv, skb, &fd, countptr, &offset);
}
+ if (unlikely(err < 0))
+ goto skb_to_fd_failed;

if (unlikely(dpa_xmit(priv, percpu_stats, queue_mapping, &fd) < 0))
goto xmit_failed;
@@ -422,6 +716,8 @@ xmit_failed:
return NETDEV_TX_OK;
}
_dpa_cleanup_tx_fd(priv, &fd);
+skb_to_fd_failed:
+enomem:
percpu_stats->tx_errors++;
dev_kfree_skb(skb);
return NETDEV_TX_OK;
--
1.7.11.7

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