Re: [PATCH] ucc_geth: Rework the TX logic.

From: Li Yang <hidden>
Date: 2009-03-27 10:39:08
Also in: netdev

On Fri, Mar 27, 2009 at 6:23 PM, Joakim Tjernlund
[off-list ref] wrote:

pku.leo@gmail.com wrote on 27/03/2009 10:45:12:

quoted

On Fri, Mar 27, 2009 at 1:44 AM, Joakim Tjernlund
[off-list ref] wrote:

quoted

The line:
=C2=A0if ((bd =3D=3D ugeth->txBd[txQ]) && (netif_queue_stopped(dev) =

=3D=3D 0))

quoted

=C2=A0 =C2=A0 =C2=A0 break;
in ucc_geth_tx() didn not make sense to me. Rework & cleanup
this logic to something understandable.
---

Reworked the patch according to Antons comments.

=C2=A0drivers/net/ucc_geth.c | =C2=A0 66

+++++++++++++++++++++++++++--------------------

quoted

=C2=A01 files changed, 38 insertions(+), 28 deletions(-)

diff --git a/drivers/net/ucc_geth.c b/drivers/net/ucc_geth.c
index 7fc91aa..465de3a 100644
--- a/drivers/net/ucc_geth.c
+++ b/drivers/net/ucc_geth.c

@@ -161,6 +161,17 @@ static struct ucc_geth_info ugeth_primary_info =

=3D

quoted

=C2=A0static struct ucc_geth_info ugeth_info[8];

+
+static inline u32 __iomem *bd2buf(u8 __iomem *bd)
+{
+ =C2=A0 =C2=A0 =C2=A0 return (u32 __iomem *)(bd+4);
+}
+
+static inline u32 __iomem *bd2status(u8 __iomem *bd)
+{
+ =C2=A0 =C2=A0 =C2=A0 return (u32 __iomem *)bd;
+}


When the driver was reviewed for upstream merge, I was told to remove
this kind of thing in favor of direct struct qe_bd access. =C2=A0So do w=

quoted

really have a guideline on this? =C2=A0Or it's just a matter of personal
preference?

This is a bit better than the current type casts. Moving over to qe_bd
accesses is a bigger cleanup that will have to be a seperate patch.
I am not sure it is an all win as you probably loose the ability
to read both status and len in one access.

quoted

+
=C2=A0#ifdef DEBUG
=C2=A0static void mem_disp(u8 *addr, int size)
=C2=A0{

@@ -3048,6 +3059,7 @@ static int ucc_geth_start_xmit(struct sk_buff

*skb, struct net_device *dev)

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0u8 __iomem *bd; =C2=A0 =C2=A0 =C2=A0 =C2=A0=

 =C2=A0 =C2=A0 =C2=A0 =C2=A0 /* BD pointer */

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0u32 bd_status;
=C2=A0 =C2=A0 =C2=A0 =C2=A0u8 txQ =3D 0;
+ =C2=A0 =C2=A0 =C2=A0 int tx_ind;

=C2=A0 =C2=A0 =C2=A0 =C2=A0ugeth_vdbg("%s: IN", __func__);

@@ -3057,21 +3069,19 @@ static int ucc_geth_start_xmit(struct sk_buff

*skb, struct net_device *dev)

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0/* Start from the next BD that should be fi=

lled */

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0bd =3D ugeth->txBd[txQ];
- =C2=A0 =C2=A0 =C2=A0 bd_status =3D in_be32((u32 __iomem *)bd);
+ =C2=A0 =C2=A0 =C2=A0 bd_status =3D in_be32(bd2status(bd));
=C2=A0 =C2=A0 =C2=A0 =C2=A0/* Save the skb pointer so we can free it l=

ater */

quoted

- =C2=A0 =C2=A0 =C2=A0 ugeth->tx_skbuff[txQ][ugeth->skb_curtx[txQ]] =

=3D skb;

quoted

+ =C2=A0 =C2=A0 =C2=A0 tx_ind =3D ugeth->skb_curtx[txQ];
+ =C2=A0 =C2=A0 =C2=A0 ugeth->tx_skbuff[txQ][tx_ind] =3D skb;

=C2=A0 =C2=A0 =C2=A0 =C2=A0/* Update the current skb pointer (wrapping=

 if this was the

last) */

quoted

- =C2=A0 =C2=A0 =C2=A0 ugeth->skb_curtx[txQ] =3D
- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 (ugeth->skb_curtx[txQ] +
- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A01) & TX_RING_MOD_MASK(ugeth=

->ug_info->bdRingLenTx[txQ]);

quoted

+ =C2=A0 =C2=A0 =C2=A0 tx_ind =3D (tx_ind + 1) &

TX_RING_MOD_MASK(ugeth->ug_info->bdRingLenTx[txQ]);

quoted

+ =C2=A0 =C2=A0 =C2=A0 ugeth->skb_curtx[txQ] =3D tx_ind;

=C2=A0 =C2=A0 =C2=A0 =C2=A0/* set up the buffer descriptor */
- =C2=A0 =C2=A0 =C2=A0 out_be32(&((struct qe_bd __iomem *)bd)->buf,
- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=

=A0 dma_map_single(&ugeth->dev->dev, skb->data,

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=

=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 skb->len, DMA_TO_DEVICE));

quoted

-
- =C2=A0 =C2=A0 =C2=A0 /* printk(KERN_DEBUG"skb->data is 0x%x\n",skb->=

data); */

quoted

+ =C2=A0 =C2=A0 =C2=A0 out_be32(bd2buf(bd),
+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0dma_map_singl=

e(&ugeth->dev->dev, skb->data,

quoted

+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=

=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 skb->len, DMA_TO_DEVICE));

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0bd_status =3D (bd_status & T_W) | T_R | T_I=

 | T_L | skb->len;

quoted

@@ -3088,9 +3098,9 @@ static int ucc_geth_start_xmit(struct sk_buff

*skb, struct net_device *dev)

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0/* If the next BD still needs to be cleaned=

 up, then the bds

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 are full. =C2=A0We need to tell the=

 kernel to stop sending us

stuff. */

quoted

- =C2=A0 =C2=A0 =C2=A0 if (bd =3D=3D ugeth->confBd[txQ]) {
- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 if (!netif_queue_st=

opped(dev))

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=

=A0 =C2=A0 netif_stop_queue(dev);

quoted

+
+ =C2=A0 =C2=A0 =C2=A0 if (!in_be32(bd2buf(bd))) {
+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 netif_stop_queue(de=

v);

quoted

Why does this make more sense? =C2=A0The BD with a NULL buffer means the
ring is full? =C2=A0It's not the normal case.

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0}

=C2=A0 =C2=A0 =C2=A0 =C2=A0ugeth->txBd[txQ] =3D bd;

@@ -3198,41 +3208,41 @@ static int ucc_geth_tx(struct net_device *dev,

u8 txQ)

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0struct ucc_geth_private *ugeth =3D netdev_p=

riv(dev);

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0u8 __iomem *bd; =C2=A0 =C2=A0 =C2=A0 =C2=A0=

 /* BD pointer */

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0u32 bd_status;
+ =C2=A0 =C2=A0 =C2=A0 int tx_ind, num_freed;

=C2=A0 =C2=A0 =C2=A0 =C2=A0bd =3D ugeth->confBd[txQ];
- =C2=A0 =C2=A0 =C2=A0 bd_status =3D in_be32((u32 __iomem *)bd);
-
+ =C2=A0 =C2=A0 =C2=A0 bd_status =3D in_be32(bd2status(bd));
+ =C2=A0 =C2=A0 =C2=A0 tx_ind =3D ugeth->skb_dirtytx[txQ];
+ =C2=A0 =C2=A0 =C2=A0 num_freed =3D 0;
=C2=A0 =C2=A0 =C2=A0 =C2=A0/* Normal processing. */
=C2=A0 =C2=A0 =C2=A0 =C2=A0while ((bd_status & T_R) =3D=3D 0) {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0/* BD contains =

already transmitted buffer. =C2=A0 */

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0/* Handle the t=

ransmitted buffer and release */

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0/* the BD to be=

 used with the current frame =C2=A0*/

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 if ((bd =3D=3D uget=

h->txBd[txQ]) &&

(netif_queue_stopped(dev) =3D=3D 0))

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=

=A0 =C2=A0 break;

quoted

+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 if (bd =3D=3D ugeth=

->txBd[txQ])

quoted

+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=

=A0 =C2=A0 break; /* Queue is empty */

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0dev->stats.tx_p=

ackets++;

quoted

=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0/* Free the sk =

buffer associated with this TxBD */

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 dev_kfree_skb(ugeth=

->

quoted

quoted
-

tx_skbuff[txQ][ugeth->skb_dirtytx[txQ]]);

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 ugeth->tx_skbuff[tx=

Q][ugeth->skb_dirtytx[txQ]] =3D NULL;

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 ugeth->skb_dirtytx[=

txQ] =3D

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 (uget=

h->skb_dirtytx[txQ] +

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=

=A01) &

TX_RING_MOD_MASK(ugeth->ug_info->bdRingLenTx[txQ]);

quoted

-
- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 /* We freed a buffe=

r, so now we can restart

transmission */

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 if (netif_queue_sto=

pped(dev))

quoted

- =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=

=A0 =C2=A0 netif_wake_queue(dev);

quoted

+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 dev_kfree_skb(ugeth=

->tx_skbuff[txQ][tx_ind]);

quoted

+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 ugeth->tx_skbuff[tx=

Q][tx_ind] =3D NULL;

quoted

+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 out_be32(bd2buf(bd)=

, 0); /* Mark it free */

quoted

Now I see why you depend on the buffer to judge if the BD ring is
full. =C2=A0If you want to do this, make sure it's well documented in co=

de,

quoted

or others will be confused. =C2=A0And as Anton already commented, in/out
access is slow. =C2=A0I think the original way can be fixed if you think
it's broken, and will have better performance.

The code could use a better comment, but I really think this method
is superior and more robust. The problem is that in/out functions is
much slower than it has to be for QE IO memory.

The original way is broken and I tired to fix it but it always broke
as soon one applied some load.

The only difference I see between your method and the original code is
that you update the cleanup progress on every BD.  The original code
updates progress only after all sent BDs are processed.  You can try
move ugeth->confBd[txQ] =3D bd; into the loop then it will be the same
as your proposed code.

- Leo

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