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From: Peter Maydell <peter.maydell@linaro.org>
Date: Thu, 12 Jan 2017 10:42:41 +0000
Message-ID: <CAFEAcA8asry6LGTuv+SLVyemNVFk9Q7WhU74Cc2YA_yud8qPMg@mail.gmail.com>
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Subject: Re: [Qemu-devel] [PATCH] pflash_cfi01: fix per device sector length
 in CFI table
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To: David Engraf <david.engraf@sysgo.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Max Reitz <mreitz@redhat.com>, Qemu-block <qemu-block@nongnu.org>, QEMU Developers <qemu-devel@nongnu.org>, Andrew Jones <drjones@redhat.com>

On 12 January 2017 at 10:35, David Engraf <david.engraf@sysgo.com> wrote:
> The CFI entry for sector length must be set to sector length per device.
> This is important for boards using multiple devices like the ARM Vexpress
> board (width = 4, device-width = 2).
>
> Linux and u-boots calculate the size ratio by dividing both values:
>
> size_ratio = info->portwidth / info->chipwidth;
>
> After that the sector length will be multiplied by the size_ratio, thus the
> CFI entry for sector length is doubled. When Linux or u-boot send a sector
> erase, they expect to erase the doubled sector length, but QEMU only erases
> the board specified sector length.
>
> This patch fixes the sector length in the CFI table to match the length per
> device, equal to blocks_per_device.

Thanks for the patch. I haven't checked against the pflash spec yet,
but this looks like it's probably the right thing.

The only two machines which use a setup with multiple devices (ie
which specify device_width to the pflash_cfi01) are vexpress and virt.
For all other machines this patch leaves the behaviour unchanged.

Q: do we need to have some kind of nasty hack so that pre-2.9 virt
still gets the old broken values in the CFI table, for version and
migration compatibility? Ccing Drew for an opinion...

thanks
-- PMM