net: systemport: Remove need for DMA descriptor

All we do is write the length/status and address bits to a DMA
descriptor only to write its contents into on-chip registers right
after, eliminate this unnecessary step.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 8 insertions, 58 deletions

diff --git a/drivers/net/ethernet/broadcom/bcmsysport.c b/drivers/net/ethernet/broadcom/bcmsysport.c
index dfe46dacf5cf..4e87a303f83e 100644
--- a/drivers/net/ethernet/broadcom/bcmsysport.c
+++ b/drivers/net/ethernet/broadcom/bcmsysport.c
@@ -116,15 +116,6 @@ static inline void dma_desc_set_addr(struct bcm_sysport_priv *priv,
         writel_relaxed(lower_32_bits(addr), d + DESC_ADDR_LO);
 }
 
-static inline void tdma_port_write_desc_addr(struct bcm_sysport_priv *priv,
-                                             struct dma_desc *desc,
-                                             unsigned int port)
-{
-        /* Ports are latched, so write upper address first */
-        tdma_writel(priv, desc->addr_status_len, TDMA_WRITE_PORT_HI(port));
-        tdma_writel(priv, desc->addr_lo, TDMA_WRITE_PORT_LO(port));
-}
-
 /* Ethtool operations */
 static void bcm_sysport_set_rx_csum(struct net_device *dev,
                                     netdev_features_t wanted)
@@ -1291,11 +1282,10 @@ static netdev_tx_t bcm_sysport_xmit(struct sk_buff *skb,
         struct bcm_sysport_tx_ring *ring;
         struct bcm_sysport_cb *cb;
         struct netdev_queue *txq;
-        struct dma_desc *desc;
+        u32 len_status, addr_lo;
         unsigned int skb_len;
         unsigned long flags;
         dma_addr_t mapping;
-        u32 len_status;
         u16 queue;
         int ret;
 
@@ -1338,10 +1328,7 @@ static netdev_tx_t bcm_sysport_xmit(struct sk_buff *skb,
         dma_unmap_addr_set(cb, dma_addr, mapping);
         dma_unmap_len_set(cb, dma_len, skb_len);
 
-        /* Fetch a descriptor entry from our pool */
-        desc = ring->desc_cpu;
-
-        desc->addr_lo = lower_32_bits(mapping);
+        addr_lo = lower_32_bits(mapping);
         len_status = upper_32_bits(mapping) & DESC_ADDR_HI_MASK;
         len_status |= (skb_len << DESC_LEN_SHIFT);
         len_status |= (DESC_SOP | DESC_EOP | TX_STATUS_APP_CRC) <<
@@ -1354,16 +1341,9 @@ static netdev_tx_t bcm_sysport_xmit(struct sk_buff *skb,
                 ring->curr_desc = 0;
         ring->desc_count--;
 
-        /* Ensure write completion of the descriptor status/length
-         * in DRAM before the System Port WRITE_PORT register latches
-         * the value
-         */
-        wmb();
-        desc->addr_status_len = len_status;
-        wmb();
-
-        /* Write this descriptor address to the RING write port */
-        tdma_port_write_desc_addr(priv, desc, ring->index);
+        /* Ports are latched, so write upper address first */
+        tdma_writel(priv, len_status, TDMA_WRITE_PORT_HI(ring->index));
+        tdma_writel(priv, addr_lo, TDMA_WRITE_PORT_LO(ring->index));
 
         /* Check ring space and update SW control flow */
         if (ring->desc_count == 0)
@@ -1489,28 +1469,14 @@ static int bcm_sysport_init_tx_ring(struct bcm_sysport_priv *priv,
                                     unsigned int index)
 {
         struct bcm_sysport_tx_ring *ring = &priv->tx_rings[index];
-        struct device *kdev = &priv->pdev->dev;
         size_t size;
-        void *p;
         u32 reg;
 
         /* Simple descriptors partitioning for now */
         size = 256;
 
-        /* We just need one DMA descriptor which is DMA-able, since writing to
-         * the port will allocate a new descriptor in its internal linked-list
-         */
-        p = dma_alloc_coherent(kdev, sizeof(struct dma_desc), &ring->desc_dma,
-                               GFP_KERNEL);
-        if (!p) {
-                netif_err(priv, hw, priv->netdev, "DMA alloc failed\n");
-                return -ENOMEM;
-        }
-
         ring->cbs = kcalloc(size, sizeof(struct bcm_sysport_cb), GFP_KERNEL);
         if (!ring->cbs) {
-                dma_free_coherent(kdev, sizeof(struct dma_desc),
-                                  ring->desc_cpu, ring->desc_dma);
                 netif_err(priv, hw, priv->netdev, "CB allocation failed\n");
                 return -ENOMEM;
         }
@@ -1523,7 +1489,6 @@ static int bcm_sysport_init_tx_ring(struct bcm_sysport_priv *priv,
         ring->size = size;
         ring->clean_index = 0;
         ring->alloc_size = ring->size;
-        ring->desc_cpu = p;
         ring->desc_count = ring->size;
         ring->curr_desc = 0;
 
@@ -1578,8 +1543,8 @@ static int bcm_sysport_init_tx_ring(struct bcm_sysport_priv *priv,
         napi_enable(&ring->napi);
 
         netif_dbg(priv, hw, priv->netdev,
-                  "TDMA cfg, size=%d, desc_cpu=%p switch q=%d,port=%d\n",
-                  ring->size, ring->desc_cpu, ring->switch_queue,
+                  "TDMA cfg, size=%d, switch q=%d,port=%d\n",
+                  ring->size, ring->switch_queue,
                   ring->switch_port);
 
         return 0;
@@ -1589,7 +1554,6 @@ static void bcm_sysport_fini_tx_ring(struct bcm_sysport_priv *priv,
                                      unsigned int index)
 {
         struct bcm_sysport_tx_ring *ring = &priv->tx_rings[index];
-        struct device *kdev = &priv->pdev->dev;
         u32 reg;
 
         /* Caller should stop the TDMA engine */
@@ -1611,12 +1575,6 @@ static void bcm_sysport_fini_tx_ring(struct bcm_sysport_priv *priv,
 
         kfree(ring->cbs);
         ring->cbs = NULL;
-
-        if (ring->desc_dma) {
-                dma_free_coherent(kdev, sizeof(struct dma_desc),
-                                  ring->desc_cpu, ring->desc_dma);
-                ring->desc_dma = 0;
-        }
         ring->size = 0;
         ring->alloc_size = 0;
 
diff --git a/drivers/net/ethernet/broadcom/bcmsysport.h b/drivers/net/ethernet/broadcom/bcmsysport.h
index 0b192fea9c5d..6f3141c86436 100644
--- a/drivers/net/ethernet/broadcom/bcmsysport.h
+++ b/drivers/net/ethernet/broadcom/bcmsysport.h
@@ -516,12 +516,6 @@ struct bcm_rsb {
 
 #define TDMA_DEBUG                      0x64c
 
-/* Transmit/Receive descriptor */
-struct dma_desc {
-        u32     addr_status_len;
-        u32     addr_lo;
-};
-
 /* Number of Receive hardware descriptor words */
 #define SP_NUM_HW_RX_DESC_WORDS         1024
 #define SP_LT_NUM_HW_RX_DESC_WORDS      256
@@ -530,7 +524,7 @@ struct dma_desc {
 #define SP_NUM_TX_DESC                  1536
 #define SP_LT_NUM_TX_DESC               256
 
-#define WORDS_PER_DESC                  (sizeof(struct dma_desc) / sizeof(u32))
+#define WORDS_PER_DESC                  2
 
 /* Rx/Tx common counter group.*/
 struct bcm_sysport_pkt_counters {
@@ -718,7 +712,6 @@ struct bcm_sysport_net_dim {
 struct bcm_sysport_tx_ring {
         spinlock_t      lock;           /* Ring lock for tx reclaim/xmit */
         struct napi_struct napi;        /* NAPI per tx queue */
-        dma_addr_t      desc_dma;       /* DMA cookie */
         unsigned int    index;          /* Ring index */
         unsigned int    size;           /* Ring current size */
         unsigned int    alloc_size;     /* Ring one-time allocated size */
@@ -727,7 +720,6 @@ struct bcm_sysport_tx_ring {
         unsigned int    c_index;        /* Last consumer index */
         unsigned int    clean_index;    /* Current clean index */
         struct bcm_sysport_cb *cbs;     /* Transmit control blocks */
-        struct dma_desc *desc_cpu;      /* CPU view of the descriptor */
         struct bcm_sysport_priv *priv;  /* private context backpointer */
         unsigned long   packets;        /* packets statistics */
         unsigned long   bytes;          /* bytes statistics */