[PATCH net v2] net: dsa: tag_rtl4_a: Fix egress tags

I noticed that only port 0 worked on the RTL8366RB since we
started to use custom tags.

It turns out that the format of egress custom tags is actually
different from ingress custom tags. While the lower bits just
contain the port number in ingress tags, egress tags need to
indicate destination port by setting the bit for the
corresponding port.

It was working on port 0 because port 0 added 0x00 as port
number in the lower bits, and if you do this the packet appears
at all ports, including the intended port. Ooops.

Fix this and all ports work again. Use the define for shifting
the "type A" into place while we're at it.

Tested on the D-Link DIR-685 by sending traffic to each of
the ports in turn. It works.

Fixes: 86dd9868b878 ("net: dsa: tag_rtl4_a: Support also egress tags")
Cc: DENG Qingfang <dqfext@gmail.com>
Cc: Mauri Sandberg <redacted>
Signed-off-by: Linus Walleij <redacted>
---
ChangeLog v1->v2:
- Drop the removal of bit 9 (2 << 8) so as to not stir up unwanted
  side effects.
---
 net/dsa/tag_rtl4_a.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/dsa/tag_rtl4_a.c b/net/dsa/tag_rtl4_a.c
index 57c46b4ab2b3..e34b80fa52e1 100644
--- a/net/dsa/tag_rtl4_a.c
+++ b/net/dsa/tag_rtl4_a.c

@@ -54,9 +54,10 @@ static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb,
 	p = (__be16 *)tag;
 	*p = htons(RTL4_A_ETHERTYPE);
 
-	out = (RTL4_A_PROTOCOL_RTL8366RB << 12) | (2 << 8);
-	/* The lower bits is the port number */
-	out |= (u8)dp->index;
+	out = (RTL4_A_PROTOCOL_RTL8366RB << RTL4_A_PROTOCOL_SHIFT) | (2 << 8);
+	/* The lower bits indicate the port number */
+	out |= BIT(dp->index);
+
 	p = (__be16 *)(tag + 2);
 	*p = htons(out);
 

-- 
2.31.1

On 8/31/2021 11:50 AM, Linus Walleij wrote:

I noticed that only port 0 worked on the RTL8366RB since we
started to use custom tags.

It turns out that the format of egress custom tags is actually
different from ingress custom tags. While the lower bits just
contain the port number in ingress tags, egress tags need to
indicate destination port by setting the bit for the
corresponding port.

It was working on port 0 because port 0 added 0x00 as port
number in the lower bits, and if you do this the packet appears
at all ports, including the intended port. Ooops.

Fix this and all ports work again. Use the define for shifting
the "type A" into place while we're at it.

Tested on the D-Link DIR-685 by sending traffic to each of
the ports in turn. It works.

Fixes: 86dd9868b878 ("net: dsa: tag_rtl4_a: Support also egress tags")
Cc: DENG Qingfang <dqfext@gmail.com>
Cc: Mauri Sandberg <redacted>
Signed-off-by: Linus Walleij <redacted>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Tue, 31 Aug 2021 20:50:50 +0200 you wrote:

I noticed that only port 0 worked on the RTL8366RB since we
started to use custom tags.

It turns out that the format of egress custom tags is actually
different from ingress custom tags. While the lower bits just
contain the port number in ingress tags, egress tags need to
indicate destination port by setting the bit for the
corresponding port.

[...]

Here is the summary with links:
  - [net,v2] net: dsa: tag_rtl4_a: Fix egress tags
    https://git.kernel.org/netdev/net/c/0e90dfa7a8d8

You are awesome, thank you!
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