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Date:      Sun, 31 Jul 2016 19:21:13 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-arm@FreeBSD.org
Subject:   [Bug 211484] Zynq/Zybo cannot mount USB drives as root
Message-ID:  <bug-211484-7@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D211484

            Bug ID: 211484
           Summary: Zynq/Zybo cannot mount USB drives as root
           Product: Base System
           Version: CURRENT
          Hardware: arm
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: arm
          Assignee: freebsd-arm@FreeBSD.org
          Reporter: thoma555-bsd@yahoo.com

Created attachment 173141
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D173141&action=
=3Dedit
patch to zynq-7000.dtsi

A Zynq/Zybo system cannot mount a USB drive/stick as the root filesystem.  =
The
problem is the the ehci driver tries to DMA to a location in the first half
megabyte of memory space which has several caveats on Zynq including a hole
between 256K-512K that is inaccessible by bus masters.

Originally, I tried to avoid something like this happening by starting memo=
ry
at 0x100000 in the Zynq DTS file.  But, ubldr "fixes up" memory ranges using
information from u-boot (retrieved by a sysinfo call to the API).  That cau=
ses
the kernel to allocate the first megabyte.

The simplest work-around seems to be to add a =E2=80=9Cmemreserve=E2=80=9D =
property to the DTS.
 Also, It turns out that only the first half megabyte needs to be excluded.

--=20
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