sfc: Move all TX DMA length limiting into tx.c

Replace the duplicated logic in efx_enqueue_skb() and
efx_tx_queue_insert() with an inline function, efx_max_tx_len().

Remove the failed attempt at abstracting hardware-specifics and put
all the magic numbers in efx_max_tx_len().

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 23 insertions, 14 deletions

diff --git a/drivers/net/sfc/tx.c b/drivers/net/sfc/tx.c
index ae554eec0563..303919a34df6 100644
--- a/drivers/net/sfc/tx.c
+++ b/drivers/net/sfc/tx.c
@@ -124,6 +124,24 @@ static void efx_tsoh_free(struct efx_tx_queue *tx_queue,
 }
 
 
+static inline unsigned
+efx_max_tx_len(struct efx_nic *efx, dma_addr_t dma_addr)
+{
+        /* Depending on the NIC revision, we can use descriptor
+         * lengths up to 8K or 8K-1.  However, since PCI Express
+         * devices must split read requests at 4K boundaries, there is
+         * little benefit from using descriptors that cross those
+         * boundaries and we keep things simple by not doing so.
+         */
+        unsigned len = (~dma_addr & 0xfff) + 1;
+
+        /* Work around hardware bug for unaligned buffers. */
+        if (EFX_WORKAROUND_5391(efx) && (dma_addr & 0xf))
+                len = min_t(unsigned, len, 512 - (dma_addr & 0xf));
+
+        return len;
+}
+
 /*
  * Add a socket buffer to a TX queue
  *
@@ -146,7 +164,7 @@ static netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue,
         skb_frag_t *fragment;
         struct page *page;
         int page_offset;
-        unsigned int len, unmap_len = 0, fill_level, insert_ptr, misalign;
+        unsigned int len, unmap_len = 0, fill_level, insert_ptr;
         dma_addr_t dma_addr, unmap_addr = 0;
         unsigned int dma_len;
         bool unmap_single;
@@ -223,14 +241,10 @@ static netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue,
                         EFX_BUG_ON_PARANOID(!buffer->continuation);
                         EFX_BUG_ON_PARANOID(buffer->unmap_len);
 
-                        dma_len = (((~dma_addr) & efx->type->tx_dma_mask) + 1);
-                        if (likely(dma_len > len))
+                        dma_len = efx_max_tx_len(efx, dma_addr);
+                        if (likely(dma_len >= len))
                                 dma_len = len;
 
-                        misalign = (unsigned)dma_addr & efx->type->bug5391_mask;
-                        if (misalign && dma_len + misalign > 512)
-                                dma_len = 512 - misalign;
-
                         /* Fill out per descriptor fields */
                         buffer->len = dma_len;
                         buffer->dma_addr = dma_addr;
@@ -703,7 +717,7 @@ static int efx_tx_queue_insert(struct efx_tx_queue *tx_queue,
 {
         struct efx_tx_buffer *buffer;
         struct efx_nic *efx = tx_queue->efx;
-        unsigned dma_len, fill_level, insert_ptr, misalign;
+        unsigned dma_len, fill_level, insert_ptr;
         int q_space;
 
         EFX_BUG_ON_PARANOID(len <= 0);
@@ -752,12 +766,7 @@ static int efx_tx_queue_insert(struct efx_tx_queue *tx_queue,
 
                 buffer->dma_addr = dma_addr;
 
-                /* Ensure we do not cross a boundary unsupported by H/W */
-                dma_len = (~dma_addr & efx->type->tx_dma_mask) + 1;
-
-                misalign = (unsigned)dma_addr & efx->type->bug5391_mask;
-                if (misalign && dma_len + misalign > 512)
-                        dma_len = 512 - misalign;
+                dma_len = efx_max_tx_len(efx, dma_addr);
 
                 /* If there is enough space to send then do so */
                 if (dma_len >= len)