[PATCH net v5 2/5] net: macb: remove illusion about TBQPH/RBQPH being per-queue

Théo Lebrun
2025-09-10T16:16:36Z

The MACB driver acts as if TBQPH/RBQPH are configurable on a per queue
basis; this is a lie. A single register configures the upper 32 bits of
each DMA descriptor buffers for all queues.

Concrete actions:

- Drop GEM_TBQPH/GEM_RBQPH macros which have a queue index argument.
Only use MACB_TBQPH/MACB_RBQPH constants.

- Drop struct macb_queue->TBQPH/RBQPH fields.

- In macb_init_buffers(): do a single write to TBQPH and RBQPH for all
queues instead of a write per queue.

- In macb_tx_error_task(): drop the write to TBQPH.

- In macb_alloc_consistent(): if allocations give different upper
32-bits, fail. Previously, it would have lead to silent memory
corruption as queues would have used the upper 32 bits of the alloc
from queue 0 and their own low 32 bits.

- In macb_suspend(): if we use the tie off descriptor for suspend, do
the write once for all queues instead of once per queue.

Fixes: fff8019a08b6 ("net: macb: Add 64 bit addressing support for GEM")
Fixes: ae1f2a56d273 ("net: macb: Added support for many RX queues")
Reviewed-by: Sean Anderson <sean.anderson@linux.dev>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
drivers/net/ethernet/cadence/macb.h | 4 ---
drivers/net/ethernet/cadence/macb_main.c | 57 ++++++++++++++------------------
2 files changed, 24 insertions(+), 37 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index c9a5c8beb2fa8166195d1d83f187d2d0c62668a8..a7e845fee4b3a2e3d14abb49abdbaf3e8e6ea02b 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -213,10 +213,8 @@

#define GEM_ISR(hw_q) (0x0400 + ((hw_q) << 2))
#define GEM_TBQP(hw_q) (0x0440 + ((hw_q) << 2))
-#define GEM_TBQPH(hw_q) (0x04C8)
#define GEM_RBQP(hw_q) (0x0480 + ((hw_q) << 2))
#define GEM_RBQS(hw_q) (0x04A0 + ((hw_q) << 2))
-#define GEM_RBQPH(hw_q) (0x04D4)
#define GEM_IER(hw_q) (0x0600 + ((hw_q) << 2))
#define GEM_IDR(hw_q) (0x0620 + ((hw_q) << 2))
#define GEM_IMR(hw_q) (0x0640 + ((hw_q) << 2))
@@ -1214,10 +1212,8 @@ struct macb_queue {
unsigned int IDR;
unsigned int IMR;
unsigned int TBQP;
- unsigned int TBQPH;
unsigned int RBQS;
unsigned int RBQP;
- unsigned int RBQPH;

/* Lock to protect tx_head and tx_tail */
spinlock_t tx_ptr_lock;
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index c769b7dbd3baf5cafe64008e18dff939623528d4..3e634049dadf14d371eac68448f80b111f228dfd 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -495,19 +495,19 @@ static void macb_init_buffers(struct macb *bp)
struct macb_queue *queue;
unsigned int q;

+#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
+ /* Single register for all queues' high 32 bits. */
+ if (bp->hw_dma_cap & HW_DMA_CAP_64B) {
+ macb_writel(bp, RBQPH,
+ upper_32_bits(bp->queues[0].rx_ring_dma));
+ macb_writel(bp, TBQPH,
+ upper_32_bits(bp->queues[0].tx_ring_dma));
+ }
+#endif
+
for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) {
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)
- queue_writel(queue, RBQPH,
- upper_32_bits(queue->rx_ring_dma));
-#endif
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
}
}

@@ -1166,10 +1166,6 @@ static void macb_tx_error_task(struct work_struct *work)

/* Reinitialize the TX desc queue */
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
/* Make TX ring reflect state of hardware */
queue->tx_head = 0;
queue->tx_tail = 0;
@@ -2546,6 +2542,7 @@ static int macb_alloc_consistent(struct macb *bp)
{
struct macb_queue *queue;
unsigned int q;
+ u32 upper;
int size;

for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) {
@@ -2553,7 +2550,9 @@ static int macb_alloc_consistent(struct macb *bp)
queue->tx_ring = dma_alloc_coherent(&bp->pdev->dev, size,
&queue->tx_ring_dma,
GFP_KERNEL);
- if (!queue->tx_ring)
+ 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",
@@ -2567,8 +2566,11 @@ static int macb_alloc_consistent(struct macb *bp)

size = RX_RING_BYTES(bp) + bp->rx_bd_rd_prefetch;
queue->rx_ring = dma_alloc_coherent(&bp->pdev->dev, size,
- &queue->rx_ring_dma, GFP_KERNEL);
- if (!queue->rx_ring)
+ &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",
@@ -4309,12 +4311,6 @@ static int macb_init(struct platform_device *pdev)
queue->TBQP = GEM_TBQP(hw_q - 1);
queue->RBQP = GEM_RBQP(hw_q - 1);
queue->RBQS = GEM_RBQS(hw_q - 1);
-#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
- if (bp->hw_dma_cap & HW_DMA_CAP_64B) {
- queue->TBQPH = GEM_TBQPH(hw_q - 1);
- queue->RBQPH = GEM_RBQPH(hw_q - 1);
- }
-#endif
} else {
/* queue0 uses legacy registers */
queue->ISR = MACB_ISR;
@@ -4323,12 +4319,6 @@ static int macb_init(struct platform_device *pdev)
queue->IMR = MACB_IMR;
queue->TBQP = MACB_TBQP;
queue->RBQP = MACB_RBQP;
-#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
- if (bp->hw_dma_cap & HW_DMA_CAP_64B) {
- queue->TBQPH = MACB_TBQPH;
- queue->RBQPH = MACB_RBQPH;
- }
-#endif
}

/* get irq: here we use the linux queue index, not the hardware
@@ -5452,6 +5442,11 @@ static int __maybe_unused macb_suspend(struct device *dev)
*/
tmp = macb_readl(bp, NCR);
macb_writel(bp, NCR, tmp & ~(MACB_BIT(TE) | MACB_BIT(RE)));
+#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
+ if (!(bp->caps & MACB_CAPS_QUEUE_DISABLE))
+ macb_writel(bp, RBQPH,
+ upper_32_bits(bp->rx_ring_tieoff_dma));
+#endif
for (q = 0, queue = bp->queues; q < bp->num_queues;
++q, ++queue) {
/* Disable RX queues */
@@ -5461,10 +5456,6 @@ static int __maybe_unused macb_suspend(struct device *dev)
/* Tie off RX queues */
queue_writel(queue, RBQP,
lower_32_bits(bp->rx_ring_tieoff_dma));
-#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
- queue_writel(queue, RBQPH,
- upper_32_bits(bp->rx_ring_tieoff_dma));
-#endif
}
/* Disable all interrupts */
queue_writel(queue, IDR, -1);

--
2.51.0