NAK: [SRU][F:linux-bluefield][PATCH v1 0/1] mlxbf_gige: increase MDIO polling rate to 5us

[Tim Gardner]

This patch, though simple enough, has had no upstream review and should 
therefore be an 'UBUNTU: SAUCE:' patch until such time as it is included 
in net-next or linux-next. Furthermore, define a macro for the POLL time 
instead of duplicating magic numbers in the code.

rtg

On 5/19/22 16:49, David Thompson wrote:
> BugLink: https://bugs.launchpad.net/bugs/1974246
> 
> SRU Justification:
> 
> [Impact]
> 
> There is MDIO logic within the mlxbf_gige driver that currently
> polls for completed transactions every 100us. This has been
> reviewed and tested in the lab and found to be inefficient.
> 
> [Fix]
> 
> The fix is to modify the driver logic to increase the MDIO
> polling rate to 5us. With this change the amount of
> time spent waiting for the MDIO BUSY signal to de-assert
> drops from ~100us to ~27us for each operation.
> 
> [Test Case]
> 
> The driver should function as before, specifically:
> * driver probes successfully
> * oob_net0 link comes up, as seen with "ifconfig -a"
> * reset and power cycle testing toggle PHY hardware,
>    and oob_net0 link still comes up
> 
> [Regression Potential]
> 
> This change affects all MDIO transactions to the board-level
> PHY device, and as such, could cause a regression with PHY
> communications. However, this change has been heavily tested.
> 
> David Thompson (1):
>    mlxbf_gige: increase MDIO polling rate to 5us
> 
>   drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_mdio.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 

-- 
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Tim Gardner
Canonical, Inc