Re: [PATCH 03/12] fs_enet: Add FEC TX Alignment workaround for MPC5121.
I was having deja-vu with this and realized that I have fixed at least some of the objections to this patch. Wolfgang you may want to look at the patch in my 5121 git tree here: http://git.denx.de/?p=linux-mpc512x.git;a=commit;h=2950be3be42af7449941c3340998c27ef918f10f It does runtime tx packet alignment It also has fewer ifdefs and trys to share more code. It also has a header that explains everything including that fact that there is not a runtime conflict sine the only other ppc that has fec is 8xx which is not in the same family. On Wed, May 6, 2009 at 4:42 PM, Grant Likely grant.lik...@secretlab.cawrote: On Wed, May 6, 2009 at 4:12 PM, Wolfgang Denk w...@denx.de wrote: Dear Grant Likely, In message fa686aa40905061337w6aa82f5aj787618ba108e5...@mail.gmail.com you wrote: The FEC on 5121 has problems with misaligned tx buffers. The RM says any alignment is ok but empirical results show that packet buffers ending in 0x1E will sometimes hang the FEC. Other bad alignment does not hang but will cause silent TX failures resulting in about a 1% packet loss as tested by ping -f from a remote host. This patch is a work around that copies every tx packet to an aligned skb before sending. OUCH! Yes :-( +#else +#define tx_skb_align_workaround(dev, skb) (skb) +#endif Another use of #ifdef blocks. What is the multiplatform impact? Hm... Can you recommend a better way to solve the problem? Suggestions are welcome. I'd rather see a runtime selectable workaround. ie. enable it based on the compatible property. g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. ___ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
[PATCH 03/12] fs_enet: Add FEC TX Alignment workaround for MPC5121.
From: John Rigby jri...@freescale.com
The FEC on 5121 has problems with misaligned tx buffers.
The RM says any alignment is ok but empirical results
show that packet buffers ending in 0x1E will sometimes
hang the FEC. Other bad alignment does not hang but will
cause silent TX failures resulting in about a 1% packet
loss as tested by ping -f from a remote host.
This patch is a work around that copies every tx packet
to an aligned skb before sending.
Signed-off-by: John Rigby jri...@freescale.com
Signed-off-by: Piotr Ziecik ko...@semihalf.com
Signed-off-by: Wolfgang Denk w...@denx.de
Cc: net...@vger.kernel.org
Cc: Grant Likely grant.lik...@secretlab.ca
Cc: John Rigby jcri...@gmail.com
---
drivers/net/fs_enet/Kconfig|3 ++
drivers/net/fs_enet/fs_enet-main.c | 41
drivers/net/fs_enet/mac-fec.c |2 +-
3 files changed, 45 insertions(+), 1 deletions(-)
diff --git a/drivers/net/fs_enet/Kconfig b/drivers/net/fs_enet/Kconfig
index fc073b5..79afd07 100644
--- a/drivers/net/fs_enet/Kconfig
+++ b/drivers/net/fs_enet/Kconfig
@@ -8,6 +8,9 @@ config FS_ENET_MPC5121_FEC
def_bool y if (FS_ENET PPC_MPC512x)
select FS_ENET_HAS_FEC
+config FS_ENET_FEC_TX_ALIGN_WORKAROUND
+ def_bool y if FS_ENET_MPC5121_FEC
+
config FS_ENET_HAS_SCC
bool Chip has an SCC usable for ethernet
depends on FS_ENET (CPM1 || CPM2)
diff --git a/drivers/net/fs_enet/fs_enet-main.c
b/drivers/net/fs_enet/fs_enet-main.c
index 4170d33..c83ffc3 100644
--- a/drivers/net/fs_enet/fs_enet-main.c
+++ b/drivers/net/fs_enet/fs_enet-main.c
@@ -594,6 +594,37 @@ void fs_cleanup_bds(struct net_device *dev)
/**/
+#ifdef CONFIG_FS_ENET_FEC_TX_ALIGN_WORKAROUND
+static struct sk_buff *tx_skb_align_workaround(struct net_device *dev,
+ struct sk_buff *skb)
+{
+ struct sk_buff *new_skb;
+
+ /* Alloc new skb */
+ new_skb = dev_alloc_skb(ENET_RX_FRSIZE + 32);
+ if (!new_skb) {
+ printk(KERN_WARNING DRV_MODULE_NAME
+ : %s Memory squeeze, dropping tx packet.\n,
+ dev-name);
+ return NULL;
+ }
+
+ /* Make sure new skb is properly aligned */
+ skb_align(new_skb, 32);
+
+ /* Copy data to new skb ... */
+ skb_copy_from_linear_data(skb, new_skb-data, skb-len);
+ skb_put(new_skb, skb-len);
+
+ /* ... and free an old one */
+ dev_kfree_skb_any(skb);
+
+ return new_skb;
+}
+#else
+#define tx_skb_align_workaround(dev, skb) (skb)
+#endif
+
static int fs_enet_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct fs_enet_private *fep = netdev_priv(dev);
@@ -602,6 +633,16 @@ static int fs_enet_start_xmit(struct sk_buff *skb, struct
net_device *dev)
u16 sc;
unsigned long flags;
+ skb = tx_skb_align_workaround(dev, skb);
+ if (!skb) {
+ /*
+* We have lost packet due to memory allocation error in
+* tx_skb_align_workaround(). Hopefully original skb is still
+* valid, so try transmit it later.
+*/
+ return NETDEV_TX_BUSY;
+ }
+
spin_lock_irqsave(fep-tx_lock, flags);
/*
diff --git a/drivers/net/fs_enet/mac-fec.c b/drivers/net/fs_enet/mac-fec.c
index b069088..3e86498 100644
--- a/drivers/net/fs_enet/mac-fec.c
+++ b/drivers/net/fs_enet/mac-fec.c
@@ -311,7 +311,7 @@ static void restart(struct net_device *dev)
* Enable big endian.
*/
#ifndef CONFIG_FS_ENET_MPC5121_FEC
- /* Don't care about SDMA FC. */
+ /* Don't care about SDMA Function Code. */
FW(fecp, fun_code, 0x7800);
#else
FS(fecp, dma_control, 0xC000);
--
1.6.0.6
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Re: [PATCH 03/12] fs_enet: Add FEC TX Alignment workaround for MPC5121.
On Wed, May 6, 2009 at 2:15 PM, Wolfgang Denk w...@denx.de wrote:
From: John Rigby jri...@freescale.com
The FEC on 5121 has problems with misaligned tx buffers.
The RM says any alignment is ok but empirical results
show that packet buffers ending in 0x1E will sometimes
hang the FEC. Other bad alignment does not hang but will
cause silent TX failures resulting in about a 1% packet
loss as tested by ping -f from a remote host.
This patch is a work around that copies every tx packet
to an aligned skb before sending.
OUCH!
diff --git a/drivers/net/fs_enet/fs_enet-main.c
b/drivers/net/fs_enet/fs_enet-main.c
index 4170d33..c83ffc3 100644
--- a/drivers/net/fs_enet/fs_enet-main.c
+++ b/drivers/net/fs_enet/fs_enet-main.c
@@ -594,6 +594,37 @@ void fs_cleanup_bds(struct net_device *dev)
/**/
+#ifdef CONFIG_FS_ENET_FEC_TX_ALIGN_WORKAROUND
+static struct sk_buff *tx_skb_align_workaround(struct net_device *dev,
+ struct sk_buff *skb)
+{
+ struct sk_buff *new_skb;
+
+ /* Alloc new skb */
+ new_skb = dev_alloc_skb(ENET_RX_FRSIZE + 32);
+ if (!new_skb) {
+ printk(KERN_WARNING DRV_MODULE_NAME
+ : %s Memory squeeze, dropping tx packet.\n,
+ dev-name);
+ return NULL;
+ }
+
+ /* Make sure new skb is properly aligned */
+ skb_align(new_skb, 32);
+
+ /* Copy data to new skb ... */
+ skb_copy_from_linear_data(skb, new_skb-data, skb-len);
+ skb_put(new_skb, skb-len);
+
+ /* ... and free an old one */
+ dev_kfree_skb_any(skb);
+
+ return new_skb;
+}
+#else
+#define tx_skb_align_workaround(dev, skb) (skb)
+#endif
Another use of #ifdef blocks. What is the multiplatform impact?
g.
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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Re: [PATCH 03/12] fs_enet: Add FEC TX Alignment workaround for MPC5121.
Dear Grant Likely, In message fa686aa40905061337w6aa82f5aj787618ba108e5...@mail.gmail.com you wrote: The FEC on 5121 has problems with misaligned tx buffers. The RM says any alignment is ok but empirical results show that packet buffers ending in 0x1E will sometimes hang the FEC. Other bad alignment does not hang but will cause silent TX failures resulting in about a 1% packet loss as tested by ping -f from a remote host. This patch is a work around that copies every tx packet to an aligned skb before sending. OUCH! Yes :-( +#else +#define tx_skb_align_workaround(dev, skb) (skb) +#endif Another use of #ifdef blocks. What is the multiplatform impact? Hm... Can you recommend a better way to solve the problem? Suggestions are welcome. Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de You don't have to worry about me. I might have been born yesterday... but I stayed up all night. ___ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
Re: [PATCH 03/12] fs_enet: Add FEC TX Alignment workaround for MPC5121.
On Wed, May 6, 2009 at 4:12 PM, Wolfgang Denk w...@denx.de wrote: Dear Grant Likely, In message fa686aa40905061337w6aa82f5aj787618ba108e5...@mail.gmail.com you wrote: The FEC on 5121 has problems with misaligned tx buffers. The RM says any alignment is ok but empirical results show that packet buffers ending in 0x1E will sometimes hang the FEC. Other bad alignment does not hang but will cause silent TX failures resulting in about a 1% packet loss as tested by ping -f from a remote host. This patch is a work around that copies every tx packet to an aligned skb before sending. OUCH! Yes :-( +#else +#define tx_skb_align_workaround(dev, skb) (skb) +#endif Another use of #ifdef blocks. What is the multiplatform impact? Hm... Can you recommend a better way to solve the problem? Suggestions are welcome. I'd rather see a runtime selectable workaround. ie. enable it based on the compatible property. g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. ___ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
