Re: [PATCH] hw/net: cadence: Return current Cadence GEM queue pointers

On 20/7/26 14:07, Bin Meng wrote:
> Cadence GEM queue pointer registers are programmed with the descriptor
> ring base, but reads return the descriptor currently being accessed.
> The model tracked the current positions separately while continuing to
> return the configured base.
> 
> The Linux macb driver uses the transmit queue pointer when recovering
> from a used-buffer interrupt. A stale priority-queue pointer can make
> the driver restart DMA before that queue handles its completion
> interrupt, causing queue 0 to repeatedly raise TX_USED.
> 
> The primary queue has had this mismatch since the initial model.
> Priority queue support later copied the same register-read behavior.
> 
> A single-queue machine usually handles TX_COMPLETE before TX_USED and
> empties the software queue before the restart check, which kept the
> issue hidden there.
> 
> Return the current RX and TX descriptor positions on queue-pointer reads
> and clear those positions on reset.
> 
> Fixes: e9f186e514a7 ("cadence_gem: initial version of device model")
> Fixes: 6710172501be ("cadence_gem: Add queue support")
> Cc: [email protected]
> Signed-off-by: Bin Meng <[email protected]>
> 
> ---
> 
>   hw/net/cadence_gem.c | 17 ++++++++++++++++-
>   1 file changed, 16 insertions(+), 1 deletion(-)

Reviewed-by: Philippe Mathieu-Daudé <[email protected]>

and queued, thanks.