Re: kern/54486: athn driver panics on arm

[Rin Okuyama <rokuyama%meiji.ac.jp@localhost>]

The following reply was made to PR kern/54486; it has been noted by GNATS.

From: Rin Okuyama <rokuyama%meiji.ac.jp@localhost>
To: matthew green <mrg%eterna.com.au@localhost>, Andreas Gustafsson <gson%gson.org@localhost>,
	Nick Hudson <nick.hudson%gmx.co.uk@localhost>
Cc: Christos Zoulas <christos%astron.com@localhost>, "maya%NetBSD.org@localhost"
	<maya%NetBSD.org@localhost>, "gnats-bugs%netbsd.org@localhost" <gnats-bugs%netbsd.org@localhost>
Subject: Re: kern/54486: athn driver panics on arm
Date: Sat, 24 Aug 2019 12:01:41 +0000

 On 2019/08/24 20:11, matthew green wrote:
 >> I found some related discussion in the port-arm archives, starting at:
 >>
 >>    http://mail-index.netbsd.org/port-arm/2019/01/06/msg005357.html
 >>
 >> My understanding of that discussion is that there are two alternative
 >> correct fixes: either apply the patch from the above message to add
 >> -mno-unaligned-access to CFLAGS, or stop using PMAP_NOCACHE in
 >> bus_dma.c as mentioned in:
 >>
 >>    http://mail-index.netbsd.org/port-arm/2019/01/06/msg005358.html
 >>
 >> The problem is that *neither* has been done.  Since the patch is less
 >> likely to have bad side effects, I think we should apply the patch
 >> now, and if or when the pmap change is ever made, the patch can be
 >> reverted.
 >=20
 > apparently i agreed with you back in january.  Rin, can you
 > commit your change for now.  at least until we fix pmap..
 
 IMO, adding -mno-unaligned-access to CFLAGS is not a correct fix,
 although affects on performance seems negligible as far as I can
 see (I guess that benefits by ability of unaligned access are
 canceled by penalty of it).
 
 A real fix should be using cacheble memory for DMA buffer. However,
 it breaks some drivers, at least, awge(4) and vchiq(4). Now, Nick
 is working on it.
 
 Nick, how is the progress? If it takes a long time, we need to
 consider a workaround of -mno-unaligned-access (and pull it up
 into netbsd-9).
 
 Thanks,
 rin