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Message-ID: <e7daf3f4-de9e-4c06-ae60-6fb215c7364e@linux.dev>
Date: Tue, 1 Jul 2025 12:20:37 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Théo Lebrun <theo.lebrun@...tlin.com>,
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>,
Nicolas Ferre <nicolas.ferre@...rochip.com>,
Claudiu Beznea <claudiu.beznea@...on.dev>,
Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
<palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Alexandre Ghiti <alex@...ti.fr>, Samuel Holland <samuel.holland@...ive.com>,
Richard Cochran <richardcochran@...il.com>,
Russell King <linux@...linux.org.uk>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>,
Gregory CLEMENT <gregory.clement@...tlin.com>,
Cyrille Pitchen <cyrille.pitchen@...el.com>,
Harini Katakam <harini.katakam@...inx.com>,
Rafal Ozieblo <rafalo@...ence.com>,
Haavard Skinnemoen <hskinnemoen@...el.com>, Jeff Garzik <jeff@...zik.org>
Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
linux-mips@...r.kernel.org, Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
Tawfik Bayouk <tawfik.bayouk@...ileye.com>
Subject: Re: [PATCH net-next v2 10/18] net: macb: remove illusion about
TBQPH/RBQPH being per-queue
On 7/1/25 12:15, Sean Anderson wrote:
> On 6/27/25 05:08, Théo Lebrun wrote:
>> 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.
>
> While better than silent memory corruption, this is not a good solution
> since bringing the netdev up will now randomly fail. Can we allocate the
> rings in one contiguous chunk instead?
Ah, looks like you do this in the next patch. In that case, (with the other
comments addressed)
Reviewed-by: Sean Anderson <sean.anderson@...ux.dev>
>> - 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")
>> Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
>
> As this is a bugfix, can you move it before your cleanup patches? This
> will make it easier to backport to stable kernels.
>
>> ---
>> drivers/net/ethernet/cadence/macb.h | 4 ----
>> drivers/net/ethernet/cadence/macb_main.c | 36 +++++++++++++-------------------
>> 2 files changed, 14 insertions(+), 26 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
>> index 707b3286a6b8408a3bc4bbbcb1335ae8c3cd95ad..adc70b6efd52b0b11e436c2c95bb5108c40f3490 100644
>> --- a/drivers/net/ethernet/cadence/macb.h
>> +++ b/drivers/net/ethernet/cadence/macb.h
>> @@ -209,10 +209,8 @@
>>
>> #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))
>> @@ -1208,10 +1206,8 @@ 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 a6633e076644089c796453f856a766299bae2ec6..d3b3635998cad095246edf8a75faebbcf7115355 100644
>> --- a/drivers/net/ethernet/cadence/macb_main.c
>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>> @@ -482,15 +482,15 @@ static void macb_init_buffers(struct macb *bp)
>> struct macb_queue *queue;
>> unsigned int q;
>>
>> + if (macb_dma_is_64b(bp)) {
>> + /* Single register for all queues' high 32 bits. */
>> + macb_writel(bp, RBQPH, upper_32_bits(bp->queues->rx_ring_dma));
>> + macb_writel(bp, TBQPH, upper_32_bits(bp->queues->tx_ring_dma));
>> + }
>> +
>> for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) {
>> queue_writel(queue, RBQP, lower_32_bits(queue->rx_ring_dma));
>> - if (macb_dma_is_64b(bp))
>> - queue_writel(queue, RBQPH,
>> - upper_32_bits(queue->rx_ring_dma));
>> queue_writel(queue, TBQP, lower_32_bits(queue->tx_ring_dma));
>> - if (macb_dma_is_64b(bp))
>> - queue_writel(queue, TBQPH,
>> - upper_32_bits(queue->tx_ring_dma));
>> }
>> }
>>
>> @@ -1145,8 +1145,6 @@ 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));
>> - if (macb_dma_is_64b(bp))
>> - queue_writel(queue, TBQPH, upper_32_bits(queue->tx_ring_dma));
>> /* Make TX ring reflect state of hardware */
>> queue->tx_head = 0;
>> queue->tx_tail = 0;
>> @@ -2524,7 +2522,8 @@ 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)
>> + if (!queue->tx_ring ||
>> + upper_32_bits(queue->tx_ring_dma) != upper_32_bits(bp->queues->tx_ring_dma))
>> goto out_err;
>> netdev_dbg(bp->dev,
>> "Allocated TX ring for queue %u of %d bytes at %08lx (mapped %p)\n",
>> @@ -2539,7 +2538,8 @@ 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)
>> + if (!queue->rx_ring ||
>> + upper_32_bits(queue->rx_ring_dma) != upper_32_bits(bp->queues->rx_ring_dma))
>
> Can you write this as bp->queues[0].rx_ring_dma for clarity?
>
>> goto out_err;
>> netdev_dbg(bp->dev,
>> "Allocated RX ring of %d bytes at %08lx (mapped %p)\n",
>> @@ -4269,10 +4269,6 @@ 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);
>> - if (macb_dma_is_64b(bp)) {
>> - queue->TBQPH = GEM_TBQPH(hw_q - 1);
>> - queue->RBQPH = GEM_RBQPH(hw_q - 1);
>> - }
>> } else {
>> /* queue0 uses legacy registers */
>> queue->ISR = MACB_ISR;
>> @@ -4281,10 +4277,6 @@ static int macb_init(struct platform_device *pdev)
>> queue->IMR = MACB_IMR;
>> queue->TBQP = MACB_TBQP;
>> queue->RBQP = MACB_RBQP;
>> - if (macb_dma_is_64b(bp)) {
>> - queue->TBQPH = MACB_TBQPH;
>> - queue->RBQPH = MACB_RBQPH;
>> - }
>> }
>>
>> /* get irq: here we use the linux queue index, not the hardware
>> @@ -5401,6 +5393,10 @@ 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 */
>> @@ -5410,10 +5406,6 @@ 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);
>>
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