Re: [net PATCH v2 5/6] eth: fbnic: Set AW_FLUSH_MODE alongside AW_FLUSH when flushing the mailbox

[Simon Horman <horms@kernel.org>]

On Mon, Sep 14, 2026 at 02:10:25PM -0700, Alexander Duyck wrote:
> From: Alexander Duyck <alexanderduyck@fb.com>
> 
> When tearing down the FW mailbox Rx ring, fbnic_mbx_reset_desc_ring()
> writes AW_CFG with FLUSH set and everything else, BME included, cleared.
> Clearing BME halts the device's writes to the host but leaves the staged
> requests parked in the PUL write pipeline rather than draining them, so
> on the write path FLUSH alone never terminates the outstanding requests
> and the flush the firmware waits on never completes.
> 
> Add the FLUSH_MODE definition and set both bits so the staged writes
> drain out of the pipeline on their own. BME stays cleared, so nothing
> lands on the host; it is restored later in fbnic_mbx_init_desc_ring()
> when the ring is rebuilt, once the outstanding writes are gone.
> 
> The read path is unaffected. AR_CFG has no equivalent mode bit and
> AR_FLUSH terminates the outstanding reads by itself, so it is left as
> is.
> 
> Both writes remain plain stores rather than read-modify-writes. That is
> deliberate: the matching write in fbnic_mbx_init_desc_ring() restores
> BME and the TLP attributes, and clears both flush bits as a side effect.
> 
> Fixes: 3b12f00ddd08 ("fbnic: Gate AXI read/write enabling on FW mailbox")
> Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>

Reviewed-by: Simon Horman <horms@kernel.org>