Revert "skge: fix ram buffer size calculation"

This reverts commit 7fb7ac241162dc51ec0f7644d4a97b2855213c32.

Heikki Orsila reports that it causes a regression:

  "Doing

	nc host port < /dev/zero

   on a sending machine (not skge) to an skge machine that is receiving:

	nc -l -p port >/dev/null

   with ~60 MiB/s speed, causes the interface go malfunct. A slow
   transfer doesn't cause a problem."

See

	http://bugzilla.kernel.org/show_bug.cgi?id=9321

for some more information.

There is a workaround (also reported by Heikki):

  "After some fiddling, I noticed that not changing the register write
   order on patch:

   +       skge_write32(hw, RB_ADDR(q, RB_END), end);
           skge_write32(hw, RB_ADDR(q, RB_WP), start);
           skge_write32(hw, RB_ADDR(q, RB_RP), start);
   -       skge_write32(hw, RB_ADDR(q, RB_END), end);

   fixes the visible effect..  Possibly not the root cause of the
   problem, but changing the order back fixes networking here."

but that has yet to be ack'ed or tested more widely, so the whole
problem-causing commit gets reverted until this is resolved properly.

Bisected-and-requested-by: Heikki Orsila <shdl@zakalwe.fi>
Cc: Stephen Hemminger <shemminger@linux-foundation.org>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 27 insertions, 24 deletions

diff --git a/drivers/net/skge.c b/drivers/net/skge.c
index b9961dc47606..6d62250fba07 100644
--- a/drivers/net/skge.c
+++ b/drivers/net/skge.c
@@ -2512,31 +2512,32 @@ static int skge_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 	return err;
 }
 
-/* Assign Ram Buffer allocation to queue */
-static void skge_ramset(struct skge_hw *hw, u16 q, u32 start, u32 space)
+static void skge_ramset(struct skge_hw *hw, u16 q, u32 start, size_t len)
 {
 	u32 end;
 
-	/* convert from K bytes to qwords used for hw register */
-	start *= 1024/8;
-	space *= 1024/8;
-	end = start + space - 1;
+	start /= 8;
+	len /= 8;
+	end = start + len - 1;
 
 	skge_write8(hw, RB_ADDR(q, RB_CTRL), RB_RST_CLR);
 	skge_write32(hw, RB_ADDR(q, RB_START), start);
-	skge_write32(hw, RB_ADDR(q, RB_END), end);
 	skge_write32(hw, RB_ADDR(q, RB_WP), start);
 	skge_write32(hw, RB_ADDR(q, RB_RP), start);
+	skge_write32(hw, RB_ADDR(q, RB_END), end);
 
 	if (q == Q_R1 || q == Q_R2) {
-		u32 tp = space - space/4;
-
 		/* Set thresholds on receive queue's */
-		skge_write32(hw, RB_ADDR(q, RB_RX_UTPP), tp);
-		skge_write32(hw, RB_ADDR(q, RB_RX_LTPP), space/4);
-	} else if (hw->chip_id != CHIP_ID_GENESIS)
-		/* Genesis Tx Fifo is too small for normal store/forward */
+		skge_write32(hw, RB_ADDR(q, RB_RX_UTPP),
+			     start + (2*len)/3);
+		skge_write32(hw, RB_ADDR(q, RB_RX_LTPP),
+			     start + (len/3));
+	} else {
+		/* Enable store & forward on Tx queue's because
+		 * Tx FIFO is only 4K on Genesis and 1K on Yukon
+		 */
 		skge_write8(hw, RB_ADDR(q, RB_CTRL), RB_ENA_STFWD);
+	}
 
 	skge_write8(hw, RB_ADDR(q, RB_CTRL), RB_ENA_OP_MD);
 }
@@ -2564,7 +2565,7 @@ static int skge_up(struct net_device *dev)
 	struct skge_port *skge = netdev_priv(dev);
 	struct skge_hw *hw = skge->hw;
 	int port = skge->port;
-	u32 ramaddr, ramsize, rxspace;
+	u32 chunk, ram_addr;
 	size_t rx_size, tx_size;
 	int err;
 
@@ -2619,15 +2620,14 @@ static int skge_up(struct net_device *dev)
 	spin_unlock_bh(&hw->phy_lock);
 
 	/* Configure RAMbuffers */
-	ramsize = (hw->ram_size - hw->ram_offset) / hw->ports;
-	ramaddr = hw->ram_offset + port * ramsize;
-	rxspace = 8 + (2*(ramsize - 16))/3;
-
-	skge_ramset(hw, rxqaddr[port], ramaddr, rxspace);
-	skge_ramset(hw, txqaddr[port], ramaddr + rxspace, ramsize - rxspace);
+	chunk = hw->ram_size / ((hw->ports + 1)*2);
+	ram_addr = hw->ram_offset + 2 * chunk * port;
 
+	skge_ramset(hw, rxqaddr[port], ram_addr, chunk);
 	skge_qset(skge, rxqaddr[port], skge->rx_ring.to_clean);
+
 	BUG_ON(skge->tx_ring.to_use != skge->tx_ring.to_clean);
+	skge_ramset(hw, txqaddr[port], ram_addr+chunk, chunk);
 	skge_qset(skge, txqaddr[port], skge->tx_ring.to_use);
 
 	/* Start receiver BMU */
@@ -3591,12 +3591,15 @@ static int skge_reset(struct skge_hw *hw)
 	if (hw->chip_id == CHIP_ID_GENESIS) {
 		if (t8 == 3) {
 			/* special case: 4 x 64k x 36, offset = 0x80000 */
-			hw->ram_size = 1024;
-			hw->ram_offset = 512;
+			hw->ram_size = 0x100000;
+			hw->ram_offset = 0x80000;
 		} else
 			hw->ram_size = t8 * 512;
-	} else /* Yukon */
-		hw->ram_size = t8 ? t8 * 4 : 128;
+	}
+	else if (t8 == 0)
+		hw->ram_size = 0x20000;
+	else
+		hw->ram_size = t8 * 4096;
 
 	hw->intr_mask = IS_HW_ERR;