The tx/rx ring size calculation is somewhat complex and partially hidden
behind a macro. Move that out of the {RX,TX}_RING_BYTES() macros and
macb_{alloc,free}_consistent() functions into neat separate functions.

In macb_free_consistent(), we drop the size variable and directly call
the size helpers in the arguments list. In macb_alloc_consistent(), we
keep the size variable that is used by netdev_dbg() calls.

Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
 drivers/net/ethernet/cadence/macb_main.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 3e634049dadf14d371eac68448f80b111f228dfd..73840808ea801b35a64a296dedc3a91e6e1f9f51 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -51,14 +51,10 @@ struct sifive_fu540_macb_mgmt {
 #define DEFAULT_RX_RING_SIZE	512 /* must be power of 2 */
 #define MIN_RX_RING_SIZE	64
 #define MAX_RX_RING_SIZE	8192
-#define RX_RING_BYTES(bp)	(macb_dma_desc_get_size(bp)	\
-				 * (bp)->rx_ring_size)
 
 #define DEFAULT_TX_RING_SIZE	512 /* must be power of 2 */
 #define MIN_TX_RING_SIZE	64
 #define MAX_TX_RING_SIZE	4096
-#define TX_RING_BYTES(bp)	(macb_dma_desc_get_size(bp)	\
-				 * (bp)->tx_ring_size)
 
 /* level of occupied TX descriptors under which we wake up TX process */
 #define MACB_TX_WAKEUP_THRESH(bp)	(3 * (bp)->tx_ring_size / 4)
@@ -2470,11 +2466,20 @@ static void macb_free_rx_buffers(struct macb *bp)
 	}
 }
 
+static unsigned int macb_tx_ring_size_per_queue(struct macb *bp)
+{
+	return macb_dma_desc_get_size(bp) * bp->tx_ring_size + bp->tx_bd_rd_prefetch;
+}
+
+static unsigned int macb_rx_ring_size_per_queue(struct macb *bp)
+{
+	return macb_dma_desc_get_size(bp) * bp->rx_ring_size + bp->rx_bd_rd_prefetch;
+}
+
 static void macb_free_consistent(struct macb *bp)
 {
 	struct macb_queue *queue;
 	unsigned int q;
-	int size;
 
 	if (bp->rx_ring_tieoff) {
 		dma_free_coherent(&bp->pdev->dev, macb_dma_desc_get_size(bp),
@@ -2488,14 +2493,14 @@ static void macb_free_consistent(struct macb *bp)
 		kfree(queue->tx_skb);
 		queue->tx_skb = NULL;
 		if (queue->tx_ring) {
-			size = TX_RING_BYTES(bp) + bp->tx_bd_rd_prefetch;
-			dma_free_coherent(&bp->pdev->dev, size,
+			dma_free_coherent(&bp->pdev->dev,
+					  macb_tx_ring_size_per_queue(bp),
 					  queue->tx_ring, queue->tx_ring_dma);
 			queue->tx_ring = NULL;
 		}
 		if (queue->rx_ring) {
-			size = RX_RING_BYTES(bp) + bp->rx_bd_rd_prefetch;
-			dma_free_coherent(&bp->pdev->dev, size,
+			dma_free_coherent(&bp->pdev->dev,
+					  macb_rx_ring_size_per_queue(bp),
 					  queue->rx_ring, queue->rx_ring_dma);
 			queue->rx_ring = NULL;
 		}
@@ -2546,7 +2551,7 @@ static int macb_alloc_consistent(struct macb *bp)
 	int size;
 
 	for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) {
-		size = TX_RING_BYTES(bp) + bp->tx_bd_rd_prefetch;
+		size = macb_tx_ring_size_per_queue(bp);
 		queue->tx_ring = dma_alloc_coherent(&bp->pdev->dev, size,
 						    &queue->tx_ring_dma,
 						    GFP_KERNEL);
@@ -2564,7 +2569,7 @@ static int macb_alloc_consistent(struct macb *bp)
 		if (!queue->tx_skb)
 			goto out_err;
 
-		size = RX_RING_BYTES(bp) + bp->rx_bd_rd_prefetch;
+		size = macb_rx_ring_size_per_queue(bp);
 		queue->rx_ring = dma_alloc_coherent(&bp->pdev->dev, size,
 						    &queue->rx_ring_dma,
 						    GFP_KERNEL);

-- 
2.51.0

Hi Theo,


On 9/10/2025 9:45 PM, Théo Lebrun wrote:
<...>
>   #define DEFAULT_TX_RING_SIZE	512 /* must be power of 2 */
>   #define MIN_TX_RING_SIZE	64
>   #define MAX_TX_RING_SIZE	4096
> -#define TX_RING_BYTES(bp) (macb_dma_desc_get_size(bp) \
> - * (bp)->tx_ring_size)
>   
>   /* level of occupied TX descriptors under which we wake up TX process */
>   #define MACB_TX_WAKEUP_THRESH(bp)	(3 * (bp)->tx_ring_size / 4)
> @@ -2470,11 +2466,20 @@ static void macb_free_rx_buffers(struct macb *bp)
>   	}
>   }
>   
> +static unsigned int macb_tx_ring_size_per_queue(struct macb *bp)
> +{
> + return macb_dma_desc_get_size(bp) * bp->tx_ring_size + bp- 
>  >tx_bd_rd_prefetch;
> +}
> +
> +static unsigned int macb_rx_ring_size_per_queue(struct macb *bp)
> +{
> + return macb_dma_desc_get_size(bp) * bp->rx_ring_size + bp- 
>  >rx_bd_rd_prefetch;
> +}
> +


it would be good to have these functions as inline.
May be as a separate patch.

<...>
-- 
🙏 Vineeth

Hello Vineeth,

On Thu Sep 11, 2025 at 8:43 AM CEST, Karumanchi, Vineeth wrote:
> On 9/10/2025 9:45 PM, Théo Lebrun wrote:
>>   #define DEFAULT_TX_RING_SIZE	512 /* must be power of 2 */
>>   #define MIN_TX_RING_SIZE	64
>>   #define MAX_TX_RING_SIZE	4096
>> -#define TX_RING_BYTES(bp) (macb_dma_desc_get_size(bp) \
>> - * (bp)->tx_ring_size)
>>   
>>   /* level of occupied TX descriptors under which we wake up TX process */
>>   #define MACB_TX_WAKEUP_THRESH(bp)	(3 * (bp)->tx_ring_size / 4)
>> @@ -2470,11 +2466,20 @@ static void macb_free_rx_buffers(struct macb *bp)
>>   	}
>>   }
>>   
>> +static unsigned int macb_tx_ring_size_per_queue(struct macb *bp)
>> +{
>> + return macb_dma_desc_get_size(bp) * bp->tx_ring_size + bp- 
>>  >tx_bd_rd_prefetch;
>> +}
>> +
>> +static unsigned int macb_rx_ring_size_per_queue(struct macb *bp)
>> +{
>> + return macb_dma_desc_get_size(bp) * bp->rx_ring_size + bp- 
>>  >rx_bd_rd_prefetch;
>> +}
>> +
>
> it would be good to have these functions as inline.
> May be as a separate patch.

I don't see why? Compilers are clever pieces, they'll know to inline it.

If we added inline to macb_{tx,rx}_ring_size_per_queue(), should we also
add it to macb_dma_desc_get_size()? I do not know, but my compiler
decided to inline it as well. It might make other decisions on other
platforms.

Last point I see: those two functions are not called in the hotpath,
only at alloc & free. If we talk about inline for the theoretical speed
gain, then it doesn't matter in that case. If it is a code size aspect,
then once again the compiler is more aware than myself.

I don't like the tone, but it is part of the kernel doc and is on topic:
https://www.kernel.org/doc/html/latest/process/coding-style.html#the-inline-disease

Thanks Vineeth!

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

On Thu, 11 Sep 2025 11:14:52 +0200 Théo Lebrun wrote:
> > it would be good to have these functions as inline.
> > May be as a separate patch.  
> 
> I don't see why? Compilers are clever pieces, they'll know to inline it.
> 
> If we added inline to macb_{tx,rx}_ring_size_per_queue(), should we also
> add it to macb_dma_desc_get_size()? I do not know, but my compiler
> decided to inline it as well. It might make other decisions on other
> platforms.
> 
> Last point I see: those two functions are not called in the hotpath,
> only at alloc & free. If we talk about inline for the theoretical speed
> gain, then it doesn't matter in that case. If it is a code size aspect,
> then once again the compiler is more aware than myself.
> 
> I don't like the tone, but it is part of the kernel doc and is on topic:
> https://www.kernel.org/doc/html/latest/process/coding-style.html#the-inline-disease

👍️ FWIW, please don't sprinkle inlines.