From: Mark Kettenis <mark.kettenis@xs4all.nl>
Subject: Re: Intel AX210 DMA memory allocation fails
To: "Jan Schreiber" <jes@posteo.de>
Cc: tech@openbsd.org
Date: Wed, 15 Jul 2026 16:09:51 +0200

> Content-Type: text/plain; charset=UTF-8
> Date: Wed, 15 Jul 2026 13:20:10 +0000
> 
> On my RK3588 board with an Intel AX210 wifi card I reliably get:
> 
> iwx0: could not allocate DMA memory for firmware image loader
> iwx0: could not init context info
> iwx0: failed to load init firmware
> iwx0: could not allocate context info DMA memory
> iwx0: could not init context info
> iwx0: failed to load init firmware
> 
> Retrying to allocate the memory works and the error does not show up any
> more. Another way to fix this would be look at the state of the wifi
> connection after boot and retry in e.g. /etc/rc.local with some logic.

The proper way to solve this is to use BUS_DMA_WAITOK instead of
BUS_DMA_NOWAIT.  Some careful analysis is needed to make sure that
sleeping is ok in all the codepaths that call iwx_dma_contig_alloc().


> diff --git sys/dev/pci/if_iwx.c sys/dev/pci/if_iwx.c
> index 2bf28bd4480..7c2ac7e9af6 100644
> --- sys/dev/pci/if_iwx.c
> +++ sys/dev/pci/if_iwx.c
> @@ -143,6 +143,9 @@ int iwx_debug = 1;
>  #define DPRINTFN(n, x)	do { ; } while (0)
>  #endif
> 
> +#define IWX_DMA_RETRY_MAX	100
> +#define IWX_DMA_RETRY_DELAY	10000	/* usec (10ms) */
> +
>  #include <dev/pci/if_iwxreg.h>
>  #include <dev/pci/if_iwxvar.h>
> 
> @@ -1869,9 +1872,10 @@ int
>  iwx_dma_contig_alloc(bus_dma_tag_t tag, struct iwx_dma_info *dma,
>      bus_size_t size, bus_size_t alignment)
>  {
> -	int nsegs, err;
> +	int nsegs, err, retry = 0;
>  	caddr_t va;
> 
> +again:
>  	dma->tag = tag;
>  	dma->size = size;
> 
> @@ -1907,6 +1911,10 @@ iwx_dma_contig_alloc(bus_dma_tag_t tag, struct iwx_dma_info *dma,
>  	return 0;
> 
>  fail:	iwx_dma_contig_free(dma);
> +	if (err == ENOMEM && retry++ < IWX_DMA_RETRY_MAX) {
> +		DELAY(IWX_DMA_RETRY_DELAY);
> +		goto again;
> +	}
>  	return err;
>  }
> 
> 
>