From: Landry Breuil <landry@openbsd.org>
Subject: Re: smmu(4): don't always set DMA coherent tag
To: Patrick Wildt <patrick@blueri.se>
Cc: tech@openbsd.org, kettenis@openbsd.org
Date: Thu, 28 Aug 2025 08:28:31 +0200

Le Wed, Aug 27, 2025 at 02:03:39PM +0200, Patrick Wildt a écrit :
> Hi,
> 
> SMMUs don't necessarily influence device DMA coherency attributes.
> I assume we have been lucky so far that our machines that have an
> SMMUv2 usually have devices with DMA coherency.  On the RK3588
> this is not the case, and us always adding the COHERENT flag makes
> devices fail to work when used with smmu(4) enabled.
> 
> Please give this a run on machines where "dmesg | grep ^smmu" shows
> some output.

i dont have regressions on the omnibook x14 with that patch and the
previous, but smmu is still disabled. should i test with it enabled ?
that's only adding 'early 1' to the 'smmu* at fdt?' line right ?