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authorAlex Elder <elder@linaro.org>2021-11-24 13:44:16 -0600
committerJakub Kicinski <kuba@kernel.org>2021-11-25 20:04:52 -0800
commitfe68c43ce38865299de03b691e5069d3daca015a (patch)
tree5fd569e7a35684a3e498f0d6c9d925116ef8a48f /net/tipc
parent4c9d631adbc277b33704a971cde6dd8ce44fbb8f (diff)
net: ipa: support enhanced channel flow control
IPA v4.2 introduced GSI channel flow control, used instead of IPA endpoint DELAY mode to prevent a TX channel from injecting packets into the IPA core. It used a new FLOW_CONTROLLED channel state which could be entered using GSI generic commands. IPA v4.11 extended the channel flow control model. Rather than having a distinct FLOW_CONTROLLED channel state, each channel has a "flow control" property that can be enabled or not--independent of the channel state. The AP (or modem) can modify this property using the same GSI generic commands as before. The AP only uses channel flow control on modem TX channels, and only when recovering from a modem crash. The AP has no way to discover the state of a modem channel, so the fact that (starting with IPA v4.11) flow control no longer uses a distinct channel state is invisible to the AP. So enhanced flow control generally does not change the way AP uses flow control. There are a few small differences, however: - There is a notion of "primary" or "secondary" flow control, and when enabling or disabling flow control that must be specified in a new field in the GSI generic command register. For now, we always specify 0 (meaning "primary"). - When disabling flow control, it's possible a request will need to be retried. We retry up to 5 times in this case. - Another new generic command allows the current flow control state to be queried. We do not use this. Other than the need for retries, the code essentially works the same way as before. Signed-off-by: Alex Elder <elder@linaro.org> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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