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PR/54486 CVS commit: [netbsd-9] src/sys
The following reply was made to PR kern/54486; it has been noted by GNATS.
From: "Martin Husemann" <martin%netbsd.org@localhost>
Subject: PR/54486 CVS commit: [netbsd-9] src/sys
Date: Sun, 1 Sep 2019 14:03:03 +0000
Module Name: src
Committed By: martin
Date: Sun Sep 1 14:03:02 UTC 2019
src/sys/arch/arm/conf [netbsd-9]: Makefile.arm
src/sys/dev/usb [netbsd-9]: if_axe.c
Pull up following revision(s) (requested by rin in ticket #146):
sys/arch/arm/conf/Makefile.arm: revision 1.50
sys/dev/usb/if_axe.c: revision 1.120
Workaround for alignment faults on ARMv6+, at least occur with
axe(4) and athn(4) drivers.
For ARMv6+, unaligned access is enabled by default. However, it
cannot be used for non-cacheable memory, which is used as DMA
buffers. This results in alignment faults above. A real fix is
to use cacheable memory as DMA buffers. However, it breaks some
drivers, awge(4) and vchiq(4) at least.
Until we figure out problems and fix them, we choose a fail-safe
workaround here; forbid unaligned memory access for whole kernel.
Affects on performance is negligibly small as far as we can see.
Revert workaround introduced in rev 1.94:
This is a problem specific to ARMv6+, and addressed by
arch/arm/conf/Makefile.arm rev 1.50:
To generate a diff of this commit:
cvs rdiff -u -r1.49 -r126.96.36.199 src/sys/arch/arm/conf/Makefile.arm
cvs rdiff -u -r188.8.131.52 -r184.108.40.206 src/sys/dev/usb/if_axe.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
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