Re: kern/50038: udl (DisplayLink GX-DVI_U2B) alignment fault on earmv6hf NETWALKER

[Nick Hudson <skrll%netbsd.org@localhost>]

The following reply was made to PR kern/50038; it has been noted by GNATS.

From: Nick Hudson <skrll%netbsd.org@localhost>
To: MOCHIDA Shuji <mochid%netside.co.jp@localhost>
Cc: gnats-bugs%NetBSD.org@localhost, kern-bug-people%netbsd.org@localhost,
 gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/50038: udl (DisplayLink GX-DVI_U2B) alignment fault on
 earmv6hf NETWALKER
Date: Wed, 16 Nov 2016 14:25:59 +0000

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 On 11/16/16 13:32, MOCHIDA Shuji wrote:
 >>>    In these functions, (curcpu()->ci_ctrl & CPU_CONTROL_AFLT_ENABLE) is zero.
 >> We should be running with SCTLR.A =0 and SCTLR.U = 1, i.e.
 >> CPU_CONTROL_AFLT_ENABLE unset and CPU_CONTROL_UNAL_ENABLE set, but
 >> I think the usb transfer buffer is being marked as device/strongly ordered memory and
 >> we get an unaligned access fault because of this.
 > be32enc(sc->sc_cmd_buf, val) -- sc_cmd_buf is allocated in
 > usbdi.c:414 usbd_alloc_buffer() using kmem_alloc()..
 
 nearly... usbd_alloc_buller() using  usb_allocmem_flags()
 
 https://nxr.netbsd.org/xref/src/sys/dev/usb/usbdi.c#403
 
 You could try removing BUS_DMA_COHERENT from the bus_dmamem_map call - 
 see diff.
 
 > -mochid
 >
 >
 
 Nick
 
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