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

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Message-ID: <437a8d6d-8d59-4ae3-beda-d9eab1300109@suse.de>
Date: Tue, 19 Aug 2025 13:36:25 +0300
From: Stanimir Varbanov <svarbanov@...e.de>
To: Nicolas Ferre <nicolas.ferre@...rochip.com>,
 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

Hi Nicolas,

Thank you for the review!

On 8/19/25 11:29 AM, Nicolas Ferre wrote:
> 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.

Hmm, that reminds me that I have to update the patch body because the
credits should go to Jonathan Bell and Phil Elwell if I decipher
properly the description in raspberrypi downstream kernel :)

> 
>> Signed-off-by: Stanimir Varbanov <svarbanov@...e.de>
> 
> A "Fixes" tag might be interesting here.

Sure, I'll do that.

> 
>> ---
>>   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.

Ack.

> 
>> +#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
> 

regards,
~Stan