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From: Felix Fietkau <nbd@nbd.name>
Date: Sun, 12 Apr 2015 09:58:56 +0200
Subject: [PATCH] bgmac: simplify tx ring index handling
Keep incrementing ring->start and ring->end instead of pointing it to
the actual ring slot entry. This simplifies the calculation of the
number of free slots.
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/drivers/net/ethernet/broadcom/bgmac.c
+++ b/drivers/net/ethernet/broadcom/bgmac.c
@@ -142,11 +142,10 @@ static netdev_tx_t bgmac_dma_tx_add(stru
{
struct device *dma_dev = bgmac->core->dma_dev;
struct net_device *net_dev = bgmac->net_dev;
- struct bgmac_slot_info *slot = &ring->slots[ring->end];
- int free_slots;
+ int index = ring->end % BGMAC_TX_RING_SLOTS;
+ struct bgmac_slot_info *slot = &ring->slots[index];
int nr_frags;
u32 flags;
- int index = ring->end;
int i;
if (skb->len > BGMAC_DESC_CTL1_LEN) {
@@ -159,12 +158,10 @@ static netdev_tx_t bgmac_dma_tx_add(stru
nr_frags = skb_shinfo(skb)->nr_frags;
- if (ring->start <= ring->end)
- free_slots = ring->start - ring->end + BGMAC_TX_RING_SLOTS;
- else
- free_slots = ring->start - ring->end;
-
- if (free_slots <= nr_frags + 1) {
+ /* ring->end - ring->start will return the number of valid slots,
+ * even when ring->end overflows
+ */
+ if (ring->end - ring->start + nr_frags + 1 >= BGMAC_TX_RING_SLOTS) {
bgmac_err(bgmac, "TX ring is full, queue should be stopped!\n");
netif_stop_queue(net_dev);
return NETDEV_TX_BUSY;
@@ -200,7 +197,7 @@ static netdev_tx_t bgmac_dma_tx_add(stru
}
slot->skb = skb;
-
+ ring->end += nr_frags + 1;
netdev_sent_queue(net_dev, skb->len);
wmb();
@@ -208,13 +205,12 @@ static netdev_tx_t bgmac_dma_tx_add(stru
/* Increase ring->end to point empty slot. We tell hardware the first
* slot it should *not* read.
*/
- ring->end = (index + 1) % BGMAC_TX_RING_SLOTS;
bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_TX_INDEX,
ring->index_base +
- ring->end * sizeof(struct bgmac_dma_desc));
+ (ring->end % BGMAC_TX_RING_SLOTS) *
+ sizeof(struct bgmac_dma_desc));
- free_slots -= nr_frags + 1;
- if (free_slots < 8)
+ if (ring->end - ring->start >= BGMAC_TX_RING_SLOTS - 8)
netif_stop_queue(net_dev);
return NETDEV_TX_OK;
@@ -256,17 +252,17 @@ static void bgmac_dma_tx_free(struct bgm
empty_slot &= BGMAC_DMA_TX_STATDPTR;
empty_slot /= sizeof(struct bgmac_dma_desc);
- while (ring->start != empty_slot) {
- struct bgmac_slot_info *slot = &ring->slots[ring->start];
- u32 ctl1 = le32_to_cpu(ring->cpu_base[ring->start].ctl1);
- int len = ctl1 & BGMAC_DESC_CTL1_LEN;
+ while (ring->start != ring->end) {
+ int slot_idx = ring->start % BGMAC_TX_RING_SLOTS;
+ struct bgmac_slot_info *slot = &ring->slots[slot_idx];
+ u32 ctl1;
+ int len;
- if (!slot->dma_addr) {
- bgmac_err(bgmac, "Hardware reported transmission for empty TX ring slot %d! End of ring: %d\n",
- ring->start, ring->end);
- goto next;
- }
+ if (slot_idx == empty_slot)
+ break;
+ ctl1 = le32_to_cpu(ring->cpu_base[slot_idx].ctl1);
+ len = ctl1 & BGMAC_DESC_CTL1_LEN;
if (ctl1 & BGMAC_DESC_CTL0_SOF)
/* Unmap no longer used buffer */
dma_unmap_single(dma_dev, slot->dma_addr, len,
@@ -284,10 +280,8 @@ static void bgmac_dma_tx_free(struct bgm
slot->skb = NULL;
}
-next:
slot->dma_addr = 0;
- if (++ring->start >= BGMAC_TX_RING_SLOTS)
- ring->start = 0;
+ ring->start++;
freed = true;
}
--- a/drivers/net/ethernet/broadcom/bgmac.h
+++ b/drivers/net/ethernet/broadcom/bgmac.h
@@ -414,10 +414,10 @@ enum bgmac_dma_ring_type {
* empty.
*/
struct bgmac_dma_ring {
- u16 num_slots;
- u16 start;
- u16 end;
+ u32 start;
+ u32 end;
+ u16 num_slots;
u16 mmio_base;
struct bgmac_dma_desc *cpu_base;
dma_addr_t dma_base;
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