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

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Message-ID: <20250925084902.GU836419@horms.kernel.org>
Date: Thu, 25 Sep 2025 09:49:02 +0100
From: Simon Horman <horms@...nel.org>
To: Théo Lebrun <theo.lebrun@...tlin.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Harini Katakam <harini.katakam@...inx.com>,
	Richard Cochran <richardcochran@...il.com>,
	Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Tawfik Bayouk <tawfik.bayouk@...ileye.com>,
	Sean Anderson <sean.anderson@...ux.dev>
Subject: Re: [PATCH net v6 2/5] net: macb: remove illusion about TBQPH/RBQPH
 being per-queue

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@...ux.dev>
> Acked-by: Nicolas Ferre <nicolas.ferre@...rochip.com>
> Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>

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