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Commit d52df4a3 authored by Scott Feldman's avatar Scott Feldman Committed by Jeff Garzik
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[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)
parent 2933d42c

drivers/net/e100.c

+9 −63
Original line number Diff line number Diff line
@@ -282,12 +282,6 @@ enum scb_status { 
	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 nic { 
	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 @@ static void e100_get_defaults(struct nic *nic) 
		((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 @@ static int e100_alloc_cbs(struct nic *nic) 
	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 @@ static int e100_rx_alloc_skb(struct nic *nic, struct rx *rx) 
		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 @@ static int e100_rx_indicate(struct nic *nic, struct rx *rx, 
	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 @@ static void e100_rx_clean(struct nic *nic, unsigned int *work_done, 
	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 @@ static void e100_rx_clean_list(struct nic *nic) 
	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 @@ static int e100_rx_alloc_list(struct nic *nic) 
	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 @@ static int e100_rx_alloc_list(struct nic *nic) 
	}



	nic->rx_to_use = nic->rx_to_clean = nic->rxs;

	nic->ru_running = RU_SUSPENDED;



	return 0;

}
@@ -1963,10 +1913,6 @@ static irqreturn_t e100_intr(int irq, void *dev_id) 
	/* 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 @@ static int e100_up(struct nic *nic) 
	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 @@ static int e100_loopback_test(struct nic *nic, enum loopback loopback_mode) 
		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;