| Message ID | 20210913143156.1264570-1-linus.walleij@linaro.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 339133f6c318612f9a4556c300753beda27abc01 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next] net: dsa: tag_rtl4_a: Drop bit 9 from egress frames | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | success | CCed 7 of 7 maintainers |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 8 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
On Mon, Sep 13, 2021 at 04:31:56PM +0200, Linus Walleij wrote: > This drops the code setting bit 9 on egress frames on the > Realtek "type A" (RTL8366RB) frames. > > This bit was set on ingress frames for unknown reason, > and was set on egress frames as the format of ingress > and egress frames was believed to be the same. As that > assumption turned out to be false, and since this bit > seems to have zero effect on the behaviour of the switch > let's drop this bit entirely. > > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Andrew
On 9/13/2021 7:31 AM, Linus Walleij wrote: > This drops the code setting bit 9 on egress frames on the > Realtek "type A" (RTL8366RB) frames. > > This bit was set on ingress frames for unknown reason, > and was set on egress frames as the format of ingress > and egress frames was believed to be the same. As that > assumption turned out to be false, and since this bit > seems to have zero effect on the behaviour of the switch > let's drop this bit entirely. > > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Hello: This patch was applied to netdev/net-next.git (refs/heads/master): On Mon, 13 Sep 2021 16:31:56 +0200 you wrote: > This drops the code setting bit 9 on egress frames on the > Realtek "type A" (RTL8366RB) frames. > > This bit was set on ingress frames for unknown reason, > and was set on egress frames as the format of ingress > and egress frames was believed to be the same. As that > assumption turned out to be false, and since this bit > seems to have zero effect on the behaviour of the switch > let's drop this bit entirely. > > [...] Here is the summary with links: - [net-next] net: dsa: tag_rtl4_a: Drop bit 9 from egress frames https://git.kernel.org/netdev/net-next/c/339133f6c318 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
On Mon, Sep 13, 2021 at 04:31:56PM +0200, Linus Walleij wrote: > This drops the code setting bit 9 on egress frames on the > Realtek "type A" (RTL8366RB) frames. FYI, on RTL8366S, bit 9 on egress frames is disable learning. > This bit was set on ingress frames for unknown reason, I think it could be the reason why the frame is forwarded to the CPU. > and was set on egress frames as the format of ingress > and egress frames was believed to be the same. As that > assumption turned out to be false, and since this bit > seems to have zero effect on the behaviour of the switch > let's drop this bit entirely. > > Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
On Wed, Sep 15, 2021 at 9:20 AM DENG Qingfang <dqfext@gmail.com> wrote: > On Mon, Sep 13, 2021 at 04:31:56PM +0200, Linus Walleij wrote: > > This drops the code setting bit 9 on egress frames on the > > Realtek "type A" (RTL8366RB) frames. > > FYI, on RTL8366S, bit 9 on egress frames is disable learning. > > > This bit was set on ingress frames for unknown reason, > > I think it could be the reason why the frame is forwarded to the CPU. Hm I suspect it disable learning on RTL8366RB as well. Do we have some use for that feature in DSA taggers? Yours, Linus Walleij
On Thu, Sep 23, 2021 at 11:59:36PM +0200, Linus Walleij wrote: > On Wed, Sep 15, 2021 at 9:20 AM DENG Qingfang <dqfext@gmail.com> wrote: > > On Mon, Sep 13, 2021 at 04:31:56PM +0200, Linus Walleij wrote: > > > > This drops the code setting bit 9 on egress frames on the > > > Realtek "type A" (RTL8366RB) frames. > > > > FYI, on RTL8366S, bit 9 on egress frames is disable learning. > > > > > This bit was set on ingress frames for unknown reason, > > > > I think it could be the reason why the frame is forwarded to the CPU. > > Hm I suspect it disable learning on RTL8366RB as well. Suspicion based on what? > Do we have some use for that feature in DSA taggers? Yes.
On Fri, Sep 24, 2021 at 12:12 AM Vladimir Oltean <olteanv@gmail.com> wrote: > > Hm I suspect it disable learning on RTL8366RB as well. > > Suspicion based on what? I have a not yet finished patch that dumps the FDB :) The contents change around a bit under the patch sets I have floating, but can certainly be determined when I have time to test things properly. > > Do we have some use for that feature in DSA taggers? > > Yes. OK I'll add it to my TODO, right now trying to fix up the base of the RTL8366RB patch set to handle VLANs the right way. Yours, Linus Walleij
On Fri, Sep 24, 2021 at 12:21:39AM +0200, Linus Walleij wrote: > On Fri, Sep 24, 2021 at 12:12 AM Vladimir Oltean <olteanv@gmail.com> wrote: > > > > Hm I suspect it disable learning on RTL8366RB as well. > > > > Suspicion based on what? > > I have a not yet finished patch that dumps the FDB :) > > The contents change around a bit under the patch > sets I have floating, but can certainly be determined > when I have time to test things properly. To be clear, if bit 9 is a "disable learning" bit, address learning is a process that takes place on the ingress of a packet, and in this case the ingress port is the CPU port. But the ndo_fdb_dump works with net devices, of which CPU ports have none. So it seems unlikely that you would see any difference in the output of "bridge fdb" that could be attributed to that bit. > > > Do we have some use for that feature in DSA taggers? > > > > Yes. > > OK I'll add it to my TODO, right now trying to fix up the base > of the RTL8366RB patch set to handle VLANs the right way. But you didn't ask what that use is...
On Fri, Sep 24, 2021 at 12:25 AM Vladimir Oltean <olteanv@gmail.com> wrote: > On Fri, Sep 24, 2021 at 12:21:39AM +0200, Linus Walleij wrote: > > > > Do we have some use for that feature in DSA taggers? > > > > > > Yes. > > > > OK I'll add it to my TODO, right now trying to fix up the base > > of the RTL8366RB patch set to handle VLANs the right way. > > But you didn't ask what that use is... Allright spill the beans :D I might not be the most clever at times... Yours, Linus Walleij
On Fri, Sep 24, 2021 at 12:58:00AM +0200, Linus Walleij wrote: > On Fri, Sep 24, 2021 at 12:25 AM Vladimir Oltean <olteanv@gmail.com> wrote: > > On Fri, Sep 24, 2021 at 12:21:39AM +0200, Linus Walleij wrote: > > > > > Do we have some use for that feature in DSA taggers? > > > > > > > > Yes. > > > > > > OK I'll add it to my TODO, right now trying to fix up the base > > > of the RTL8366RB patch set to handle VLANs the right way. > > > > But you didn't ask what that use is... > > Allright spill the beans :D I might not be the most clever at times... So the essence of the answer is in the discussion we've already had on your v1 attempt to disable this "unknown" bit: https://patchwork.kernel.org/project/netdevbpf/patch/20210828235619.249757-1-linus.walleij@linaro.org/ The idea is that bridges should learn only from data plane packets, and the only chance a DSA tagger has to distinguish between a data and a control packet sent by the network stack is to look at skb->offload_fwd_mark, which will be set on xmit by the bridge driver, if you implement the .port_bridge_tx_fwd_offload and .port_bridge_tx_fwd_unoffload methods, and declare a non-zero ds->max_num_bridges value (note: the API for bridge TX forwarding offload in DSA is subject to change/get simplified during this development cycle). And to offload the replication for data packets correctly, you should really re-read the discussion we had about what happens when the egress port mask set by the tagger is all-zeroes. Not to blow my own horn or anything, but I've repeated this stuff for so many times now that I wrote it down for future reference, you can find the basic concepts detailed in chapter "The data plane and the control plane" from the paper attached here (there are also pictures, not sure how much they help): https://linuxplumbersconf.org/event/11/contributions/949/
diff --git a/net/dsa/tag_rtl4_a.c b/net/dsa/tag_rtl4_a.c index f920487ae145..6d928ee3ef7a 100644 --- a/net/dsa/tag_rtl4_a.c +++ b/net/dsa/tag_rtl4_a.c @@ -54,7 +54,7 @@ static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb, p = (__be16 *)tag; *p = htons(RTL4_A_ETHERTYPE); - out = (RTL4_A_PROTOCOL_RTL8366RB << RTL4_A_PROTOCOL_SHIFT) | (2 << 8); + out = (RTL4_A_PROTOCOL_RTL8366RB << RTL4_A_PROTOCOL_SHIFT); /* The lower bits indicate the port number */ out |= BIT(dp->index);
This drops the code setting bit 9 on egress frames on the Realtek "type A" (RTL8366RB) frames. This bit was set on ingress frames for unknown reason, and was set on egress frames as the format of ingress and egress frames was believed to be the same. As that assumption turned out to be false, and since this bit seems to have zero effect on the behaviour of the switch let's drop this bit entirely. Signed-off-by: Linus Walleij <linus.walleij@linaro.org> --- net/dsa/tag_rtl4_a.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)