Re: [PATCH net v6 2/5] net: macb: remove illusion about TBQPH/RBQPH being per-queue

[Simon Horman <horms@kernel.org>]

On Tue, Sep 23, 2025 at 06:00:24PM +0200, Théo Lebrun wrote:
> The MACB driver acts as if TBQPH/RBQPH are configurable on a per queue
> basis; this is a lie. A single register configures the upper 32 bits of
> each DMA descriptor buffers for all queues.
> 
> Concrete actions:
> 
>  - Drop GEM_TBQPH/GEM_RBQPH macros which have a queue index argument.
>    Only use MACB_TBQPH/MACB_RBQPH constants.
> 
>  - Drop struct macb_queue->TBQPH/RBQPH fields.
> 
>  - In macb_init_buffers(): do a single write to TBQPH and RBQPH for all
>    queues instead of a write per queue.
> 
>  - In macb_tx_error_task(): drop the write to TBQPH.
> 
>  - In macb_alloc_consistent(): if allocations give different upper
>    32-bits, fail. Previously, it would have lead to silent memory
>    corruption as queues would have used the upper 32 bits of the alloc
>    from queue 0 and their own low 32 bits.
> 
>  - In macb_suspend(): if we use the tie off descriptor for suspend, do
>    the write once for all queues instead of once per queue.
> 
> Fixes: fff8019a08b6 ("net: macb: Add 64 bit addressing support for GEM")
> Fixes: ae1f2a56d273 ("net: macb: Added support for many RX queues")
> Reviewed-by: Sean Anderson <sean.anderson@linux.dev>
> Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
> Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>

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