[PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Stanimir Varbanov]

In case of rx queue reset and 64bit capable hardware, set the upper
32bits of DMA ring buffer address.

Cc: stable@vger.kernel.org # v4.6+
Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue to handle RX errors")
Credits-to: Phil Elwell <phil@raspberrypi.com>
Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
v1 -> v2: 
 - Added credits.
 - Use lower_32_bits() for RBQP register writes for consistency (Nicolas).
 - Added Fixes tag.

 drivers/net/ethernet/cadence/macb_main.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index ce95fad8cedd..36717e7e5811 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -1634,7 +1634,11 @@ static int macb_rx(struct macb_queue *queue, struct napi_struct *napi,
 		macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
 
 		macb_init_rx_ring(queue);
-		queue_writel(queue, RBQP, queue->rx_ring_dma);
+		queue_writel(queue, RBQP, lower_32_bits(queue->rx_ring_dma));
+#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));
 
-- 
2.47.0

Re: [PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Nicolas Ferre]

On 22/08/2025 at 11:34, Stanimir Varbanov wrote:
> In case of rx queue reset and 64bit capable hardware, set the upper
> 32bits of DMA ring buffer address.
> 
> Cc: stable@vger.kernel.org # v4.6+
> Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue to handle RX errors")
> Credits-to: Phil Elwell <phil@raspberrypi.com>
> Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
> Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
> Reviewed-by: Andrew Lunn <andrew@lunn.ch>

Looks good to me: thanks!
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>

> ---
> v1 -> v2:
>   - Added credits.
>   - Use lower_32_bits() for RBQP register writes for consistency (Nicolas).
>   - Added Fixes tag.
> 
>   drivers/net/ethernet/cadence/macb_main.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index ce95fad8cedd..36717e7e5811 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -1634,7 +1634,11 @@ static int macb_rx(struct macb_queue *queue, struct napi_struct *napi,
>                  macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
> 
>                  macb_init_rx_ring(queue);
> -               queue_writel(queue, RBQP, queue->rx_ring_dma);
> +               queue_writel(queue, RBQP, lower_32_bits(queue->rx_ring_dma));
> +#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));
> 
> --
> 2.47.0
> 

Re: [PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Claudiu Beznea]

On 22.08.2025 12:34, Stanimir Varbanov wrote:
> In case of rx queue reset and 64bit capable hardware, set the upper
> 32bits of DMA ring buffer address.
> 
> Cc: stable@vger.kernel.org # v4.6+
> Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue to handle RX errors")
> Credits-to: Phil Elwell <phil@raspberrypi.com>
> Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
> Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
> Reviewed-by: Andrew Lunn <andrew@lunn.ch>

Reviewed-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>

Re: [PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Jakub Kicinski]

On Fri, 22 Aug 2025 12:34:36 +0300 Stanimir Varbanov wrote:
> In case of rx queue reset and 64bit capable hardware, set the upper
> 32bits of DMA ring buffer address.
> 
> Cc: stable@vger.kernel.org # v4.6+
> Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue to handle RX errors")
> Credits-to: Phil Elwell <phil@raspberrypi.com>
> Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
> Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
> Reviewed-by: Andrew Lunn <andrew@lunn.ch>

> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index ce95fad8cedd..36717e7e5811 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -1634,7 +1634,11 @@ static int macb_rx(struct macb_queue *queue, struct napi_struct *napi,
>  		macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
>  
>  		macb_init_rx_ring(queue);
> -		queue_writel(queue, RBQP, queue->rx_ring_dma);
> +		queue_writel(queue, RBQP, lower_32_bits(queue->rx_ring_dma));
> +#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));
>  

Looks like a subset of Théo Lebrun's work:
https://lore.kernel.org/all/20250820-macb-fixes-v4-0-23c399429164@bootlin.com/
let's wait for his patches to get merged instead?

Re: [PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Stanimir Varbanov]

Hi Jakub,

On 8/26/25 2:53 AM, Jakub Kicinski wrote:
> On Fri, 22 Aug 2025 12:34:36 +0300 Stanimir Varbanov wrote:
>> In case of rx queue reset and 64bit capable hardware, set the upper
>> 32bits of DMA ring buffer address.
>>
>> Cc: stable@vger.kernel.org # v4.6+
>> Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue to handle RX errors")
>> Credits-to: Phil Elwell <phil@raspberrypi.com>
>> Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
>> Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
>> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
> 
>> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
>> index ce95fad8cedd..36717e7e5811 100644
>> --- a/drivers/net/ethernet/cadence/macb_main.c
>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>> @@ -1634,7 +1634,11 @@ static int macb_rx(struct macb_queue *queue, struct napi_struct *napi,
>>  		macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
>>  
>>  		macb_init_rx_ring(queue);
>> -		queue_writel(queue, RBQP, queue->rx_ring_dma);
>> +		queue_writel(queue, RBQP, lower_32_bits(queue->rx_ring_dma));
>> +#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));
>>  
> 
> Looks like a subset of Théo Lebrun's work:
> https://lore.kernel.org/all/20250820-macb-fixes-v4-0-23c399429164@bootlin.com/
> let's wait for his patches to get merged instead?

No objections for this patch, it could be postponed. But the others from
the series could be applied.

regards,
~Stan

Re: [PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Nicolas Ferre]

On 26/08/2025 at 10:35, Stanimir Varbanov wrote:
> Hi Jakub,
> 
> On 8/26/25 2:53 AM, Jakub Kicinski wrote:
>> On Fri, 22 Aug 2025 12:34:36 +0300 Stanimir Varbanov wrote:
>>> In case of rx queue reset and 64bit capable hardware, set the upper
>>> 32bits of DMA ring buffer address.
>>>
>>> Cc: stable@vger.kernel.org # v4.6+
>>> Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue to handle RX errors")
>>> Credits-to: Phil Elwell <phil@raspberrypi.com>
>>> Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
>>> Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
>>> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
>>
>>> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
>>> index ce95fad8cedd..36717e7e5811 100644
>>> --- a/drivers/net/ethernet/cadence/macb_main.c
>>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>>> @@ -1634,7 +1634,11 @@ static int macb_rx(struct macb_queue *queue, struct napi_struct *napi,
>>>               macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
>>>
>>>               macb_init_rx_ring(queue);
>>> -            queue_writel(queue, RBQP, queue->rx_ring_dma);
>>> +            queue_writel(queue, RBQP, lower_32_bits(queue->rx_ring_dma));
>>> +#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));
>>>
>>
>> Looks like a subset of Théo Lebrun's work:
>> https://lore.kernel.org/all/20250820-macb-fixes-v4-0-23c399429164@bootlin.com/
>> let's wait for his patches to get merged instead?
> 
> No objections for this patch, it could be postponed. But the others from
> the series could be applied.

Some cleanup by Théo, could interfere with sorting of compatibility 
strings...
We'll try make all this be queued in order, as Théo was first to send. 
Sorry for not having realized this earlier.

Best regards,
   Nicolas

Re: [PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Stanimir Varbanov]

Hi Nicolas,

On 8/26/25 12:13 PM, Nicolas Ferre wrote:
> On 26/08/2025 at 10:35, Stanimir Varbanov wrote:
>> Hi Jakub,
>>
>> On 8/26/25 2:53 AM, Jakub Kicinski wrote:
>>> On Fri, 22 Aug 2025 12:34:36 +0300 Stanimir Varbanov wrote:
>>>> In case of rx queue reset and 64bit capable hardware, set the upper
>>>> 32bits of DMA ring buffer address.
>>>>
>>>> Cc: stable@vger.kernel.org # v4.6+
>>>> Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue
>>>> to handle RX errors")
>>>> Credits-to: Phil Elwell <phil@raspberrypi.com>
>>>> Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
>>>> Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
>>>> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
>>>
>>>> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/
>>>> ethernet/cadence/macb_main.c
>>>> index ce95fad8cedd..36717e7e5811 100644
>>>> --- a/drivers/net/ethernet/cadence/macb_main.c
>>>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>>>> @@ -1634,7 +1634,11 @@ static int macb_rx(struct macb_queue *queue,
>>>> struct napi_struct *napi,
>>>>               macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
>>>>
>>>>               macb_init_rx_ring(queue);
>>>> -            queue_writel(queue, RBQP, queue->rx_ring_dma);
>>>> +            queue_writel(queue, RBQP, lower_32_bits(queue-
>>>> >rx_ring_dma));
>>>> +#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));
>>>>
>>>
>>> Looks like a subset of Théo Lebrun's work:
>>> https://lore.kernel.org/all/20250820-macb-fixes-
>>> v4-0-23c399429164@bootlin.com/
>>> let's wait for his patches to get merged instead?
>>
>> No objections for this patch, it could be postponed. But the others from
>> the series could be applied.
> 
> Some cleanup by Théo, could interfere with sorting of compatibility
> strings...

Théo's series touches clk properties so I do not expect conflicts.

regards,
~Stan

Re: [PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Nicolas Ferre]

On 26/08/2025 at 01:53, Jakub Kicinski wrote:
> On Fri, 22 Aug 2025 12:34:36 +0300 Stanimir Varbanov wrote:
>> In case of rx queue reset and 64bit capable hardware, set the upper
>> 32bits of DMA ring buffer address.
>>
>> Cc: stable@vger.kernel.org # v4.6+
>> Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue to handle RX errors")
>> Credits-to: Phil Elwell <phil@raspberrypi.com>
>> Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
>> Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
>> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
> 
>> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
>> index ce95fad8cedd..36717e7e5811 100644
>> --- a/drivers/net/ethernet/cadence/macb_main.c
>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>> @@ -1634,7 +1634,11 @@ static int macb_rx(struct macb_queue *queue, struct napi_struct *napi,
>>                macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
>>
>>                macb_init_rx_ring(queue);
>> -             queue_writel(queue, RBQP, queue->rx_ring_dma);
>> +             queue_writel(queue, RBQP, lower_32_bits(queue->rx_ring_dma));
>> +#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));
>>
> 
> Looks like a subset of Théo Lebrun's work:
> https://lore.kernel.org/all/20250820-macb-fixes-v4-0-23c399429164@bootlin.com/
> let's wait for his patches to get merged instead?

Yes, we can certainly wait. As RBOPH changes by Théo are key, they will 
probably remove the need for this fix altogether: but I count on you 
Stanimir to monitor that (as I don't have a 64 bit capable platform at 
hand).

Best regards,
   Nicolas

Re: [PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Stanimir Varbanov]

On 8/26/25 12:14 PM, Nicolas Ferre wrote:
> On 26/08/2025 at 01:53, Jakub Kicinski wrote:
>> On Fri, 22 Aug 2025 12:34:36 +0300 Stanimir Varbanov wrote:
>>> In case of rx queue reset and 64bit capable hardware, set the upper
>>> 32bits of DMA ring buffer address.
>>>
>>> Cc: stable@vger.kernel.org # v4.6+
>>> Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue
>>> to handle RX errors")
>>> Credits-to: Phil Elwell <phil@raspberrypi.com>
>>> Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
>>> Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
>>> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
>>
>>> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/
>>> ethernet/cadence/macb_main.c
>>> index ce95fad8cedd..36717e7e5811 100644
>>> --- a/drivers/net/ethernet/cadence/macb_main.c
>>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>>> @@ -1634,7 +1634,11 @@ static int macb_rx(struct macb_queue *queue,
>>> struct napi_struct *napi,
>>>                macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
>>>
>>>                macb_init_rx_ring(queue);
>>> -             queue_writel(queue, RBQP, queue->rx_ring_dma);
>>> +             queue_writel(queue, RBQP, lower_32_bits(queue-
>>> >rx_ring_dma));
>>> +#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));
>>>
>>
>> Looks like a subset of Théo Lebrun's work:
>> https://lore.kernel.org/all/20250820-macb-fixes-
>> v4-0-23c399429164@bootlin.com/
>> let's wait for his patches to get merged instead?
> 
> Yes, we can certainly wait. As RBOPH changes by Théo are key, they will
> probably remove the need for this fix altogether: but I count on you
> Stanimir to monitor that (as I don't have a 64 bit capable platform at
> hand).

Sure I will monitor those series. Unfortunately I also don't have MACB
64bit platform, I only have GEM.

regards,
~Stan

Re: [PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Théo Lebrun]

Hello Nicolas, Jakub, Stanimir,

On Tue Aug 26, 2025 at 11:14 AM CEST, Nicolas Ferre wrote:
> On 26/08/2025 at 01:53, Jakub Kicinski wrote:
>> On Fri, 22 Aug 2025 12:34:36 +0300 Stanimir Varbanov wrote:
>>> In case of rx queue reset and 64bit capable hardware, set the upper
>>> 32bits of DMA ring buffer address.
>>>
>>> Cc: stable@vger.kernel.org # v4.6+
>>> Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue to handle RX errors")
>>> Credits-to: Phil Elwell <phil@raspberrypi.com>
>>> Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
>>> Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
>>> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
>> 
>>> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
>>> index ce95fad8cedd..36717e7e5811 100644
>>> --- a/drivers/net/ethernet/cadence/macb_main.c
>>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>>> @@ -1634,7 +1634,11 @@ static int macb_rx(struct macb_queue *queue, struct napi_struct *napi,
>>>                macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
>>>
>>>                macb_init_rx_ring(queue);
>>> -             queue_writel(queue, RBQP, queue->rx_ring_dma);
>>> +             queue_writel(queue, RBQP, lower_32_bits(queue->rx_ring_dma));
>>> +#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));
>>>
>> 
>> Looks like a subset of Théo Lebrun's work:
>> https://lore.kernel.org/all/20250820-macb-fixes-v4-0-23c399429164@bootlin.com/
>> let's wait for his patches to get merged instead?
>
> Yes, we can certainly wait. As RBOPH changes by Théo are key, they will 
> probably remove the need for this fix altogether: but I count on you 
> Stanimir to monitor that (as I don't have a 64 bit capable platform at 
> hand).

I when looking for where this patch came from.
Commit in the raspberrypi downstream kernel:
https://github.com/raspberrypi/linux/commit/e45c98decbb16e58a79c7ec6fbe4374320e814f1

It is somewhat unreadable; the only part that seems related is the:

> net: macb: Several patches for RP1
> 64-bit RX fix

 - Is there any MACB hardware (not GEM) that uses 64-bit DMA
   descriptors? What platforms? RPi maybe?

 - Assuming such a platform exists, the next question is why does
   macb_rx() need to reinit RBQPH/0x04D4. It reinits RBQP/0x0018
   because it is the buffer pointer and increments as buffers get used.

   To reinit RBQPH would be for the case of the increment overflowing
   into the upper 32-bits. Sounds like a reasonable fix (for a really
   rare bug) if that hardware actually exists.

   This wouldn't be needed on GEM because RBQPH is shared across queues.
   So of course RBQPH would not increment with the buffer pointer.

If this patch is needed (does HW exist?), then my series doesn't address
it. I can take the patch in a potential V6 if you want. V5 got posted
today [0].

[0]: https://lore.kernel.org/lkml/20250910-macb-fixes-v5-0-f413a3601ce4@bootlin.com/

Thanks,
Have a nice day,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH v2 1/5] net: cadence: macb: Set upper 32bits of DMA ring buffer

[Théo Lebrun]

On Wed Sep 10, 2025 at 6:57 PM CEST, Théo Lebrun wrote:
> Hello Nicolas, Jakub, Stanimir,
>
> On Tue Aug 26, 2025 at 11:14 AM CEST, Nicolas Ferre wrote:
>> On 26/08/2025 at 01:53, Jakub Kicinski wrote:
>>> On Fri, 22 Aug 2025 12:34:36 +0300 Stanimir Varbanov wrote:
>>>> In case of rx queue reset and 64bit capable hardware, set the upper
>>>> 32bits of DMA ring buffer address.
>>>>
>>>> Cc: stable@vger.kernel.org # v4.6+
>>>> Fixes: 9ba723b081a2 ("net: macb: remove BUG_ON() and reset the queue to handle RX errors")
>>>> Credits-to: Phil Elwell <phil@raspberrypi.com>
>>>> Credits-to: Jonathan Bell <jonathan@raspberrypi.com>
>>>> Signed-off-by: Stanimir Varbanov <svarbanov@suse.de>
>>>> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
>>> 
>>>> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
>>>> index ce95fad8cedd..36717e7e5811 100644
>>>> --- a/drivers/net/ethernet/cadence/macb_main.c
>>>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>>>> @@ -1634,7 +1634,11 @@ static int macb_rx(struct macb_queue *queue, struct napi_struct *napi,
>>>>                macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
>>>>
>>>>                macb_init_rx_ring(queue);
>>>> -             queue_writel(queue, RBQP, queue->rx_ring_dma);
>>>> +             queue_writel(queue, RBQP, lower_32_bits(queue->rx_ring_dma));
>>>> +#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));
>>>>
>>> 
>>> Looks like a subset of Théo Lebrun's work:
>>> https://lore.kernel.org/all/20250820-macb-fixes-v4-0-23c399429164@bootlin.com/
>>> let's wait for his patches to get merged instead?
>>
>> Yes, we can certainly wait. As RBOPH changes by Théo are key, they will 
>> probably remove the need for this fix altogether: but I count on you 
>> Stanimir to monitor that (as I don't have a 64 bit capable platform at 
>> hand).
>
> I when looking for where this patch came from.
> Commit in the raspberrypi downstream kernel:
> https://github.com/raspberrypi/linux/commit/e45c98decbb16e58a79c7ec6fbe4374320e814f1
>
> It is somewhat unreadable; the only part that seems related is the:
>
>> net: macb: Several patches for RP1
>> 64-bit RX fix
>
>  - Is there any MACB hardware (not GEM) that uses 64-bit DMA
>    descriptors? What platforms? RPi maybe?
>
>  - Assuming such a platform exists, the next question is why does
>    macb_rx() need to reinit RBQPH/0x04D4. It reinits RBQP/0x0018
>    because it is the buffer pointer and increments as buffers get used.
>
>    To reinit RBQPH would be for the case of the increment overflowing
>    into the upper 32-bits. Sounds like a reasonable fix (for a really
>    rare bug) if that hardware actually exists.
>
>    This wouldn't be needed on GEM because RBQPH is shared across queues.
>    So of course RBQPH would not increment with the buffer pointer.
>
> If this patch is needed (does HW exist?), then my series doesn't address
> it. I can take the patch in a potential V6 if you want. V5 got posted
> today [0].
>
> [0]: https://lore.kernel.org/lkml/20250910-macb-fixes-v5-0-f413a3601ce4@bootlin.com/

Coming back after some sleep: my series does address this.
It updates macb_alloc_consistent() so allocs look like:

   size = bp->num_queues * macb_tx_ring_size_per_queue(bp);
   tx = dma_alloc_coherent(dev, size, &tx_dma, GFP_KERNEL);
   if (!tx || upper_32_bits(tx_dma) != upper_32_bits(tx_dma + size - 1))
      goto out_err;

   // same for rx

In the MACB (!GEM) case, bp->num_queues=1 so we will check that the
start and end of the DMA descriptor ring buffer have the same upper
32-bits.

That implies macb_rx() doesn't have to reinit RBQPH/0x04D4.

Thanks,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com