6.17-stable review patch. If anyone has any objections, please let me know.
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From: Théo Lebrun theo.lebrun@bootlin.com
[ Upstream commit 78d901897b3cae06b38f54e48a2378cf9da21175 ]
Move from 2*NUM_QUEUES dma_alloc_coherent() for DMA descriptor rings to 2 calls overall.
Issue is with how all queues share the same register for configuring the upper 32-bits of Tx/Rx descriptor rings. Taking Tx, notice how TBQPH does *not* depend on the queue index:
#define GEM_TBQP(hw_q) (0x0440 + ((hw_q) << 2)) #define GEM_TBQPH(hw_q) (0x04C8)
queue_writel(queue, TBQP, lower_32_bits(queue->tx_ring_dma)); #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT if (bp->hw_dma_cap & HW_DMA_CAP_64B) queue_writel(queue, TBQPH, upper_32_bits(queue->tx_ring_dma)); #endif
To maximise our chances of getting valid DMA addresses, we do a single dma_alloc_coherent() across queues. This improves the odds because alloc_pages() guarantees natural alignment. Other codepaths (IOMMU or dev/arch dma_map_ops) don't give high enough guarantees (even page-aligned isn't enough).
Two consideration:
- dma_alloc_coherent() gives us page alignment. Here we remove this constraint meaning each queue's ring won't be page-aligned anymore.
- This can save some tiny amounts of memory. Fewer allocations means (1) less overhead (constant cost per alloc) and (2) less wasted bytes due to alignment constraints.
Example for (2): 4 queues, default ring size (512), 64-bit DMA descriptors, 16K pages: - Before: 8 allocs of 8K, each rounded to 16K => 64K wasted. - After: 2 allocs of 32K => 0K wasted.
Fixes: 02c958dd3446 ("net/macb: add TX multiqueue support for gem") Reviewed-by: Sean Anderson sean.anderson@linux.dev Acked-by: Nicolas Ferre nicolas.ferre@microchip.com Tested-by: Nicolas Ferre nicolas.ferre@microchip.com # on sam9x75 Signed-off-by: Théo Lebrun theo.lebrun@bootlin.com Reviewed-by: Simon Horman horms@kernel.org Link: https://patch.msgid.link/20250923-macb-fixes-v6-4-772d655cdeb6@bootlin.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/cadence/macb_main.c | 80 ++++++++++++------------ 1 file changed, 41 insertions(+), 39 deletions(-)
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c index 73840808ea801..fc082a7a5a313 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -2478,32 +2478,30 @@ static unsigned int macb_rx_ring_size_per_queue(struct macb *bp)
static void macb_free_consistent(struct macb *bp) { + struct device *dev = &bp->pdev->dev; struct macb_queue *queue; unsigned int q; + size_t size;
if (bp->rx_ring_tieoff) { - dma_free_coherent(&bp->pdev->dev, macb_dma_desc_get_size(bp), + dma_free_coherent(dev, macb_dma_desc_get_size(bp), bp->rx_ring_tieoff, bp->rx_ring_tieoff_dma); bp->rx_ring_tieoff = NULL; }
bp->macbgem_ops.mog_free_rx_buffers(bp);
+ size = bp->num_queues * macb_tx_ring_size_per_queue(bp); + dma_free_coherent(dev, size, bp->queues[0].tx_ring, bp->queues[0].tx_ring_dma); + + size = bp->num_queues * macb_rx_ring_size_per_queue(bp); + dma_free_coherent(dev, size, bp->queues[0].rx_ring, bp->queues[0].rx_ring_dma); + for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) { kfree(queue->tx_skb); queue->tx_skb = NULL; - if (queue->tx_ring) { - 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) { - dma_free_coherent(&bp->pdev->dev, - macb_rx_ring_size_per_queue(bp), - queue->rx_ring, queue->rx_ring_dma); - queue->rx_ring = NULL; - } + queue->tx_ring = NULL; + queue->rx_ring = NULL; } }
@@ -2545,41 +2543,45 @@ static int macb_alloc_rx_buffers(struct macb *bp)
static int macb_alloc_consistent(struct macb *bp) { + struct device *dev = &bp->pdev->dev; + dma_addr_t tx_dma, rx_dma; struct macb_queue *queue; unsigned int q; - u32 upper; - int size; + void *tx, *rx; + size_t size; + + /* + * Upper 32-bits of Tx/Rx DMA descriptor for each queues much match! + * We cannot enforce this guarantee, the best we can do is do a single + * allocation and hope it will land into alloc_pages() that guarantees + * natural alignment of physical addresses. + */ + + 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; + netdev_dbg(bp->dev, "Allocated %zu bytes for %u TX rings at %08lx (mapped %p)\n", + size, bp->num_queues, (unsigned long)tx_dma, tx); + + size = bp->num_queues * macb_rx_ring_size_per_queue(bp); + rx = dma_alloc_coherent(dev, size, &rx_dma, GFP_KERNEL); + if (!rx || upper_32_bits(rx_dma) != upper_32_bits(rx_dma + size - 1)) + goto out_err; + netdev_dbg(bp->dev, "Allocated %zu bytes for %u RX rings at %08lx (mapped %p)\n", + size, bp->num_queues, (unsigned long)rx_dma, rx);
for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) { - size = macb_tx_ring_size_per_queue(bp); - queue->tx_ring = dma_alloc_coherent(&bp->pdev->dev, size, - &queue->tx_ring_dma, - GFP_KERNEL); - upper = upper_32_bits(queue->tx_ring_dma); - if (!queue->tx_ring || - upper != upper_32_bits(bp->queues[0].tx_ring_dma)) - goto out_err; - netdev_dbg(bp->dev, - "Allocated TX ring for queue %u of %d bytes at %08lx (mapped %p)\n", - q, size, (unsigned long)queue->tx_ring_dma, - queue->tx_ring); + queue->tx_ring = tx + macb_tx_ring_size_per_queue(bp) * q; + queue->tx_ring_dma = tx_dma + macb_tx_ring_size_per_queue(bp) * q; + + queue->rx_ring = rx + macb_rx_ring_size_per_queue(bp) * q; + queue->rx_ring_dma = rx_dma + macb_rx_ring_size_per_queue(bp) * q;
size = bp->tx_ring_size * sizeof(struct macb_tx_skb); queue->tx_skb = kmalloc(size, GFP_KERNEL); if (!queue->tx_skb) goto out_err; - - size = macb_rx_ring_size_per_queue(bp); - queue->rx_ring = dma_alloc_coherent(&bp->pdev->dev, size, - &queue->rx_ring_dma, - GFP_KERNEL); - upper = upper_32_bits(queue->rx_ring_dma); - if (!queue->rx_ring || - upper != upper_32_bits(bp->queues[0].rx_ring_dma)) - goto out_err; - netdev_dbg(bp->dev, - "Allocated RX ring of %d bytes at %08lx (mapped %p)\n", - size, (unsigned long)queue->rx_ring_dma, queue->rx_ring); } if (bp->macbgem_ops.mog_alloc_rx_buffers(bp)) goto out_err;