Re: [PATCH net v3 2/2] net:ethernet: mtk_wed: setup WDMA_RING_TX(0) for non-DBDC MT7986

[Zhi-Jun You <hujy652@gmail.com>]

On Thu, Jul 30, 2026 at 11:00:30AM +0200, Paolo Abeni wrote:
> From: AI Reviewer <ai@example.com>
> 
> This is an AI-generated review of your patch. The human sending this
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> ---
> --- Patch [2]: [PATCH net v3 2/2] net:ethernet: mtk_wed: setup WDMA_RING_TX(0) for non-DBDC MT7986 ---
> commit 30cd2d1bc8bf876e5d201d631684431920a3f165
> Author: Zhi-Jun You <hujy652@gmail.com>
> 
> net:ethernet: mtk_wed: setup WDMA_RING_TX(0) for non-DBDC MT7986
> 
> This commit fixes an issue on non-DBDC MT7986 where WDMA_RING_TX(0) is
> never set up because idx is 1, even though it is required for WED RX to
> function. It addresses this by explicitly calling mtk_wed_wdma_tx_ring_setup
> if the WED version is v2 and rx_ring[0] is unallocated.
> 
> Link: https://lore.kernel.org/r/20260711112128.971-1-hujy652@gmail.com
> Link: https://lore.kernel.org/r/20260630144831.1109-1-hujy652@gmail.com
> 
> > diff --git a/drivers/net/ethernet/mediatek/mtk_wed.c b/drivers/net/ethernet/mediatek/mtk_wed.c
> > --- a/drivers/net/ethernet/mediatek/mtk_wed.c
> > +++ b/drivers/net/ethernet/mediatek/mtk_wed.c
> [ ... ]
> > @@ -2334,6 +2334,13 @@ mtk_wed_start(struct mtk_wed_device *dev, u32 irq_mask)
> >  		if (!dev->rx_wdma[i].desc)
> >  			mtk_wed_wdma_rx_ring_setup(dev, i, 16, false);
> 
> [Severity: High]
> This is a pre-existing issue, but does this code ignore the return value
> from mtk_wed_wdma_rx_ring_setup()? 
> 
> If mtk_wed_ring_alloc() fails due to memory pressure, it returns an error
> without configuring the hardware base registers. Because the error is
> ignored, when DMA is later enabled in mtk_wed_start(), could the hardware
> attempt to fetch from unmapped physical addresses and cause an IOMMU fault?
> 
> >  
> > +	/*
> > +	 * non-DBDC MT7986 allocates only rx_ring[1] and tx_wdma[1] during setup
> > +	 * but tx_wdma[0] is also needed for WED to function.
> > +	 */
> > +	if (mtk_wed_is_v2(dev->hw) && !dev->rx_ring[0].desc)
> > +		mtk_wed_wdma_tx_ring_setup(dev, 0, MTK_WED_WDMA_RING_SIZE, !!dev->tx_wdma[0].desc);
> 
> [Severity: High]
> Does this new call to mtk_wed_wdma_tx_ring_setup() also need to check its
> return value? 
> 
> Similar to the RX ring above, if mtk_wed_ring_alloc() fails to allocate
> memory, the hardware base registers won't be configured. Since the caller
> proceeds to enable hardware DMA regardless, might this lead to the WED
> processing descriptors from unmapped memory and causing memory corruption
> or a system crash?
> 

I am not sure how to proceed with this.

Can Felix or Lorenzo comment this?

Best regards,
Zhi-Jun

> > +
> >  	if (dev->wlan.hw_rro) {
> >  		for (i = 0; i < MTK_WED_RX_PAGE_QUEUES; i++) {
> -- 
> This is an AI-generated review.
>