Re: [PATCH v5 10/11] hw/arm: Wire up BMC boot flash for npcm750-evb and quanta-gsj - Philippe Mathieu-Daudé

From: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
To: Markus Armbruster <armbru@redhat.com>,
	Havard Skinnemoen <hskinnemoen@google.com>
Cc: "Peter Maydell" <peter.maydell@linaro.org>,
	Qemu-block <qemu-block@nongnu.org>,
	"QEMU Developers" <qemu-devel@nongnu.org>,
	"CS20 KFTing" <kfting@nuvoton.com>,
	qemu-arm <qemu-arm@nongnu.org>, "Cédric Le Goater" <clg@kaod.org>,
	"IS20 Avi Fishman" <Avi.Fishman@nuvoton.com>
Subject: Re: [PATCH v5 10/11] hw/arm: Wire up BMC boot flash for npcm750-evb and quanta-gsj
Date: Tue, 14 Jul 2020 13:29:02 +0200	[thread overview]
Message-ID: <19733456-a672-595d-e721-e0ef26d7f665@amsat.org> (raw)
In-Reply-To: <875zaq78xq.fsf@dusky.pond.sub.org>

+ qemu-block experts.

On 7/14/20 11:16 AM, Markus Armbruster wrote:
> Havard Skinnemoen <hskinnemoen@google.com> writes:
> 
>> On Mon, Jul 13, 2020 at 7:57 AM Cédric Le Goater <clg@kaod.org> wrote:
>>>
>>> On 7/9/20 2:36 AM, Havard Skinnemoen wrote:
>>>> This allows these NPCM7xx-based boards to boot from a flash image, e.g.
>>>> one built with OpenBMC. For example like this:
>>>>
>>>> IMAGE=${OPENBMC}/build/tmp/deploy/images/gsj/image-bmc
>>>> qemu-system-arm -machine quanta-gsj -nographic \
>>>>       -bios ~/qemu/bootrom/npcm7xx_bootrom.bin \
>>>>       -drive file=${IMAGE},if=mtd,bus=0,unit=0,format=raw,snapshot=on
>>>>
>>>> Reviewed-by: Tyrone Ting <kfting@nuvoton.com>
>>>> Signed-off-by: Havard Skinnemoen <hskinnemoen@google.com>
>>>
>>> May be we don't need to create the flash object if dinfo is NULL.
>>
>> It's soldered on the board, so you can't really boot the board without
>> it. But if you think it's better to remove it altogether if we don't
>> have an image to load into it, I can do that.
> 
> If a device is a fixed part of the physical board, it should be a fixed
> part of the virtual board, too.

We agree so far but ... how to do it?

I never used this API, does that makes sense?

    if (!dinfo) {
        QemuOpts *opts;

        opts = qemu_opts_create(NULL, "spi-flash", 1, &error_abort);
        qdict_put_str(opts, "format", "null-co");
        qdict_put_int(opts, BLOCK_OPT_SIZE, 64 * MiB);
        qdict_put_bool(opts, NULL_OPT_ZEROES, false); // XXX

        dinfo = drive_new(opts, IF_MTD, &error_abort);
        qemu_opts_del(opts);
    }

We should probably add a public helper for that.

'XXX' because NOR flashes erase content is when hardware bit
is set, so it would be more useful to return -1/0xff... rather
than zeroes.