[netdrvr e100] experiment with doing RX in a similar manner to eepro100
I was going to say that eepro100's speedo_rx_link() does the same DMA
abuse as e100, but then I noticed one little detail: eepro100 sets both
EL (end of list) and S (suspend) bits in the RFD as it chains it to the
RFD list. e100 was only setting the EL bit. Hmmm, that's interesting.
That means that if HW reads a RFD with the S-bit set, it'll process
that RFD and then suspend the receive unit. The receive unit will
resume when SW clears the S-bit. There is no need for SW to restart
the receive unit. Which means a lot of the receive unit state tracking
code in the driver goes away.
So here's a patch against 2.6.14. (Sorry for inlining it; the mailer
I'm using now will mess with the word wrap). I can't test this on
XScale (unless someone has an e100 module for Gumstix :) . It should
be doing exactly what eepro100 does with RFDs. I don't believe this
change will introduce a performance hit because the S-bit and EL-bit go
hand-in-hand meaning if we're going to suspend because of the S- bit,
we're on the last resource anyway, so we'll have to wait for SW to
replenish.
(cherry picked from 29e79da9495261119e3b2e4e7c72507348e75976 commit)
diff --git a/drivers/net/e100.c b/drivers/net/e100.c
index 4d0e0ae..71c6d33 100644
--- a/drivers/net/e100.c
+++ b/drivers/net/e100.c
@@ -282,12 +282,6 @@
rus_mask = 0x3C,
};
-enum ru_state {
- RU_SUSPENDED = 0,
- RU_RUNNING = 1,
- RU_UNINITIALIZED = -1,
-};
-
enum scb_stat_ack {
stat_ack_not_ours = 0x00,
stat_ack_sw_gen = 0x04,
@@ -529,7 +523,6 @@
struct rx *rx_to_use;
struct rx *rx_to_clean;
struct rfd blank_rfd;
- enum ru_state ru_running;
spinlock_t cb_lock ____cacheline_aligned;
spinlock_t cmd_lock;
@@ -951,7 +944,7 @@
((nic->mac >= mac_82558_D101_A4) ? cb_cid : cb_i));
/* Template for a freshly allocated RFD */
- nic->blank_rfd.command = cpu_to_le16(cb_el);
+ nic->blank_rfd.command = cpu_to_le16(cb_el & cb_s);
nic->blank_rfd.rbd = 0xFFFFFFFF;
nic->blank_rfd.size = cpu_to_le16(VLAN_ETH_FRAME_LEN);
@@ -1746,19 +1739,11 @@
return 0;
}
-static inline void e100_start_receiver(struct nic *nic, struct rx *rx)
+static inline void e100_start_receiver(struct nic *nic)
{
- if(!nic->rxs) return;
- if(RU_SUSPENDED != nic->ru_running) return;
-
- /* handle init time starts */
- if(!rx) rx = nic->rxs;
-
- /* (Re)start RU if suspended or idle and RFA is non-NULL */
- if(rx->skb) {
- e100_exec_cmd(nic, ruc_start, rx->dma_addr);
- nic->ru_running = RU_RUNNING;
- }
+ /* Start if RFA is non-NULL */
+ if(nic->rx_to_clean->skb)
+ e100_exec_cmd(nic, ruc_start, nic->rx_to_clean->dma_addr);
}
#define RFD_BUF_LEN (sizeof(struct rfd) + VLAN_ETH_FRAME_LEN)
@@ -1787,7 +1772,7 @@
put_unaligned(cpu_to_le32(rx->dma_addr),
(u32 *)&prev_rfd->link);
wmb();
- prev_rfd->command &= ~cpu_to_le16(cb_el);
+ prev_rfd->command &= ~cpu_to_le16(cb_el & cb_s);
pci_dma_sync_single_for_device(nic->pdev, rx->prev->dma_addr,
sizeof(struct rfd), PCI_DMA_TODEVICE);
}
@@ -1825,10 +1810,6 @@
pci_unmap_single(nic->pdev, rx->dma_addr,
RFD_BUF_LEN, PCI_DMA_FROMDEVICE);
- /* this allows for a fast restart without re-enabling interrupts */
- if(le16_to_cpu(rfd->command) & cb_el)
- nic->ru_running = RU_SUSPENDED;
-
/* Pull off the RFD and put the actual data (minus eth hdr) */
skb_reserve(skb, sizeof(struct rfd));
skb_put(skb, actual_size);
@@ -1859,45 +1840,18 @@
unsigned int work_to_do)
{
struct rx *rx;
- int restart_required = 0;
- struct rx *rx_to_start = NULL;
-
- /* are we already rnr? then pay attention!!! this ensures that
- * the state machine progression never allows a start with a
- * partially cleaned list, avoiding a race between hardware
- * and rx_to_clean when in NAPI mode */
- if(RU_SUSPENDED == nic->ru_running)
- restart_required = 1;
/* Indicate newly arrived packets */
for(rx = nic->rx_to_clean; rx->skb; rx = nic->rx_to_clean = rx->next) {
- int err = e100_rx_indicate(nic, rx, work_done, work_to_do);
- if(-EAGAIN == err) {
- /* hit quota so have more work to do, restart once
- * cleanup is complete */
- restart_required = 0;
- break;
- } else if(-ENODATA == err)
+ if(e100_rx_indicate(nic, rx, work_done, work_to_do))
break; /* No more to clean */
}
- /* save our starting point as the place we'll restart the receiver */
- if(restart_required)
- rx_to_start = nic->rx_to_clean;
-
/* Alloc new skbs to refill list */
for(rx = nic->rx_to_use; !rx->skb; rx = nic->rx_to_use = rx->next) {
if(unlikely(e100_rx_alloc_skb(nic, rx)))
break; /* Better luck next time (see watchdog) */
}
-
- if(restart_required) {
- // ack the rnr?
- writeb(stat_ack_rnr, &nic->csr->scb.stat_ack);
- e100_start_receiver(nic, rx_to_start);
- if(work_done)
- (*work_done)++;
- }
}
static void e100_rx_clean_list(struct nic *nic)
@@ -1905,8 +1859,6 @@
struct rx *rx;
unsigned int i, count = nic->params.rfds.count;
- nic->ru_running = RU_UNINITIALIZED;
-
if(nic->rxs) {
for(rx = nic->rxs, i = 0; i < count; rx++, i++) {
if(rx->skb) {
@@ -1928,7 +1880,6 @@
unsigned int i, count = nic->params.rfds.count;
nic->rx_to_use = nic->rx_to_clean = NULL;
- nic->ru_running = RU_UNINITIALIZED;
if(!(nic->rxs = kcalloc(count, sizeof(struct rx), GFP_ATOMIC)))
return -ENOMEM;
@@ -1943,7 +1894,6 @@
}
nic->rx_to_use = nic->rx_to_clean = nic->rxs;
- nic->ru_running = RU_SUSPENDED;
return 0;
}
@@ -1963,10 +1913,6 @@
/* Ack interrupt(s) */
writeb(stat_ack, &nic->csr->scb.stat_ack);
- /* We hit Receive No Resource (RNR); restart RU after cleaning */
- if(stat_ack & stat_ack_rnr)
- nic->ru_running = RU_SUSPENDED;
-
if(likely(netif_rx_schedule_prep(netdev))) {
e100_disable_irq(nic);
__netif_rx_schedule(netdev);
@@ -2058,7 +2004,7 @@
if((err = e100_hw_init(nic)))
goto err_clean_cbs;
e100_set_multicast_list(nic->netdev);
- e100_start_receiver(nic, NULL);
+ e100_start_receiver(nic);
mod_timer(&nic->watchdog, jiffies);
if((err = request_irq(nic->pdev->irq, e100_intr, IRQF_SHARED,
nic->netdev->name, nic->netdev)))
@@ -2139,7 +2085,7 @@
mdio_write(nic->netdev, nic->mii.phy_id, MII_BMCR,
BMCR_LOOPBACK);
- e100_start_receiver(nic, NULL);
+ e100_start_receiver(nic);
if(!(skb = netdev_alloc_skb(nic->netdev, ETH_DATA_LEN))) {
err = -ENOMEM;