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Re: kern/54486: athn driver panics on arm

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

From: Nick Hudson <>
To: Rin Okuyama <>, matthew green <>,
 Andreas Gustafsson <>
Cc: Christos Zoulas <>, ""
 <>, "" <>
Subject: Re: kern/54486: athn driver panics on arm
Date: Sun, 25 Aug 2019 08:54:35 +0100

 On 24/08/2019 13:01, Rin Okuyama wrote:
 > On 2019/08/24 20:11, matthew green wrote:
 >>> I found some related discussion in the port-arm archives, starting at:
 >>> 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:
 >>> 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.
 >> 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).
 My focus is elsewhere at the moment, so feel free to apply the workaround.
 Perhaps we can compile a handful of drivers with -mno-unaligned-access
 and not the whole kernel?

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