Re: [PATCH] bcma: use the SoC device for DMA on MIPS

[Rosen Penev]

On Tue, Oct 13, 2026 at 5:30 AM Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote:
>
> On Fri, 2026-10-09 at 14:31 -0700, Rosen Penev wrote:
> > The MIPS BCM47xx code allocates a struct device for the SoC, sets a
> > 32-bit DMA mask on it and passes it to bcma in struct bcma_soc. bcma
> > never uses it: bus->dev stays NULL for the MIPS SoC host, so cores fall
> > back to doing DMA through their own struct device, whose
> > coherent_dma_mask is 0. Since
> > commit f8c55dc6e828 ("MIPS: use generic dma noncoherent ops for simple noncoherent platforms")
> > coherent allocations then fail:
> >
> >   bgmac_bcma bcma0:2: Allocation of TX ring 0x200 failed
> >   bgmac_bcma bcma0:2: Unable to alloc memory for DMA
> >   bgmac_bcma: probe of bcma0:2 failed with error -12
> >
> > Set bus->dev from the SoC device and do DMA through it, as the ARM SoC
> > host already does. Every SoC host now has a bus device, so drop the
> > fallback that pointed a core's dma_mask at its coherent_dma_mask.
> >
> > This addresses the review of the earlier postings: the cores' DMA masks
> > are no longer touched at all.
> >
> > Tested on an ASUS RT-N16 (BCM4718): bgmac probes and passes traffic.
> >
> > Fixes: f8c55dc6e828 ("MIPS: use generic dma noncoherent ops for simple noncoherent platforms")
> >
>
> That was in a MIPS tree, so perhaps this fix should be too? I don't
> really know what to do with it.
I thought it was weird as well. The last submission was sent to
wireless-next as well. FWIW I ran get_maintainers.pl
>
> johannes