mainlining shenanigans
ebbcac3dc2
Tobias Waldekranz says: ==================== net: dsa: Allow default tag protocol to be overridden from DT This is a continuation of the work started in this patch: https://lore.kernel.org/netdev/20210323102326.3677940-1-tobias@waldekranz.com/ In addition to the mv88e6xxx support to dynamically change the protocol, it is now possible to override the protocol from the device tree. This means that when a board vendor finds an incompatibility, they can specify a working protocol in the DT, and users will not have to worry about it. Some background information: In a system using an NXP T1023 SoC connected to a 6390X switch, we noticed that TO_CPU frames where not reaching the CPU. This only happened on hardware port 8. Looking at the DSA master interface (dpaa-ethernet) we could see that an Rx error counter was bumped at the same rate. The logs indicated a parser error. It just so happens that a TO_CPU coming in on device 0, port 8, will result in the first two bytes of the DSA tag being one of: 00 40 00 44 00 46 My guess was that since these values looked like 802.3 length fields, the controller's parser would signal an error if the frame length did not match what was in the header. This was later confirmed using two different workarounds provided by Vladimir. Unfortunately these either bypass or ignore the hardware parser and thus robs working combinations of the ability to do RSS and other nifty things. It was therefore decided to go with the option of a DT override. v1 -> v2: - Fail if the device does not support changing protocols instead of falling back to the default. (Andrew) - Only call change_tag_protocol on CPU ports. (Andrew/Vladimir) - Only allow changing the protocol on chips that have at least "undocumented" level of support for EDSA. (Andrew). - List the supported protocols in the binding documentation. I opted for only listing the protocols that I have tested. As more people test their drivers, they can add them. (Rob) v2 -> v3: - Rename "dsa,tag-protocol" -> "dsa-tag-protocol". (Rob) - Some cleanups to 4/5. (Vladimir) - Add a comment detailing how tree/driver agreement on the tag protocol is enforced. (Vladimir). ==================== Signed-off-by: David S. Miller <davem@davemloft.net> |
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Linux kernel
============
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In order to build the documentation, use ``make htmldocs`` or
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the problems which may result by upgrading your kernel.