From: Stafford Horne <shorne@gmail.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Joel Stanley <joel@jms.id.au>,
"Jason A. Donenfeld" <Jason@zx2c4.com>,
Openrisc <openrisc@lists.librecores.org>,
QEMU Development <qemu-devel@nongnu.org>
Subject: Re: [RFC PATCH 3/3] hw/openrisc: Add the OpenRISC virtual machine
Date: Tue, 7 Jun 2022 21:12:07 +0900 [thread overview]
Message-ID: <Yp9Al1UfqvIzStI7@antec> (raw)
In-Reply-To: <CAFEAcA97oraa5OSdqmubmJ2-ONTCTF4ZszwfTcZ9VhqKRFhogA@mail.gmail.com>
On Tue, Jun 07, 2022 at 11:43:08AM +0100, Peter Maydell wrote:
> So I don't have a strong view on whether these devices should
> be DEVICE_NATIVE_ENDIAN or DEVICE_LITTLE_ENDIAN (except that
> my impression is that a DEVICE_LITTLE_ENDIAN device on a
> big-endian system is a bit weird, because it means the guest
> has to byteswap everything. You see that with PCI devices because
> the PCI spec mandates LE, but not often elsewhere).
>
> If there's an official-ish spec for how goldfish devices are
> supposed to behave (does anybody have a pointer to one?) and it says
> "always little-endian" then that would probably suggest that fixing
> m68k would be nice if we can.
I think there are some conflicting thoughts on this.
In Geert's he mentioned:
Using Goldfish devices as little-endian devices should be fine.
In Arnd's mail he mentions:
https://lore.kernel.org/lkml/CAK8P3a1oN8NrUjkh2X8jHQbyz42Xo6GSa=5n0gD6vQcXRjmq1Q@mail.gmail.com/#t
... the device was clearly defined as having little-endian
registers,
Based on that I was thinking that switching to DEVICE_LITTLE_ENDIAN would make
sense.
However, in a followup mail from Laurent we see:
https://lore.kernel.org/lkml/cb884368-0226-e913-80d2-62d2b7b2e761@vivier.eu/
The reference document[1] doesn't define the endianness of goldfish.
[1] https://android.googlesource.com/platform/external/qemu/+/master/docs/GOLDFISH-VIRTUAL-HARDWARE.TXT
The documentation does not clearly specify it. So maybe maybe or1k should just
be updated on the linux side and add gf_ioread32/gf_iowrite32 big-endian
accessors.
-Stafford
next prev parent reply other threads:[~2022-06-07 12:44 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-27 17:27 [RFC PATCH 0/3] OpenRISC Semihosting and Virt Stafford Horne
2022-05-27 17:27 ` [RFC PATCH 1/3] target/openrisc: Add basic support for semihosting Stafford Horne
2022-06-02 15:39 ` Richard Henderson
2022-06-05 0:57 ` Stafford Horne
2022-06-05 14:36 ` Richard Henderson
2022-05-27 17:27 ` [RFC PATCH 2/3] hw/openrisc: Split re-usable boot time apis out to boot.c Stafford Horne
2022-06-02 15:40 ` Richard Henderson
2022-05-27 17:27 ` [RFC PATCH 3/3] hw/openrisc: Add the OpenRISC virtual machine Stafford Horne
2022-06-02 11:42 ` Joel Stanley
2022-06-02 15:49 ` Richard Henderson
2022-06-02 19:08 ` Geert Uytterhoeven
2022-06-02 19:59 ` Stafford Horne
2022-06-03 7:05 ` Geert Uytterhoeven
2022-06-05 1:58 ` Stafford Horne
2022-06-05 7:32 ` Stafford Horne
2022-06-05 8:19 ` Jason A. Donenfeld
2022-06-07 9:48 ` Jason A. Donenfeld
2022-06-07 8:11 ` Geert Uytterhoeven
2022-06-07 8:42 ` Arnd Bergmann
2022-06-07 9:47 ` Stafford Horne
2022-06-07 10:04 ` Arnd Bergmann
2022-06-07 10:43 ` Peter Maydell
2022-06-07 12:12 ` Stafford Horne [this message]
2022-06-07 14:08 ` Arnd Bergmann
2022-06-05 2:36 ` Stafford Horne
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