linux-kernel - Re: [PATCH 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

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Message-ID: <37427c1a-68af-4c50-ac6d-da5ee135c260@microchip.com>
Date: Tue, 19 Aug 2025 10:29:40 +0200
From: Nicolas Ferre <nicolas.ferre@...rochip.com>
To: Stanimir Varbanov <svarbanov@...e.de>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-rpi-kernel@...ts.infradead.org>, Broadcom internal kernel review list
	<bcm-kernel-feedback-list@...adcom.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>, Florian Fainelli <florian.fainelli@...adcom.com>,
	Andrea della Porta <andrea.porta@...e.com>, Claudiu Beznea
	<claudiu.beznea@...on.dev>, Phil Elwell <phil@...pberrypi.com>, Jonathan Bell
	<jonathan@...pberrypi.com>, Dave Stevenson <dave.stevenson@...pberrypi.com>
Subject: Re: [PATCH 1/5] net: cadence: macb: Set upper 32bits of DMA ring
 buffer

On 15/08/2025 at 15:59, Stanimir Varbanov wrote:
> In case of rx queue reset and 64bit capable hardware, set the upper
> 32bits of DMA ring buffer address.

Very nice finding! Thanks.

> Signed-off-by: Stanimir Varbanov <svarbanov@...e.de>

A "Fixes" tag might be interesting here.

> ---
>   drivers/net/ethernet/cadence/macb_main.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index ce95fad8cedd..41c0cbb5262e 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -1635,6 +1635,11 @@ static int macb_rx(struct macb_queue *queue, struct napi_struct *napi,
> 
>                  macb_init_rx_ring(queue);
>                  queue_writel(queue, RBQP, queue->rx_ring_dma);

For the sake of consistency, I would add lower_32_bits() to this call, 
as I see it for each use of RBQP or TBQP.

> +#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
> +               if (bp->hw_dma_cap & HW_DMA_CAP_64B)
> +                       macb_writel(bp, RBQPH,
> +                                   upper_32_bits(queue->rx_ring_dma));
> +#endif
> 
>                  macb_writel(bp, NCR, ctrl | MACB_BIT(RE));

Best regards,
   Nicolas