Re: [Qemu-devel] [PATCH] pflash_cfi01: fix per device sector length in CFI table

[Andrew Jones <drjones@redhat.com>]

On Thu, Jan 12, 2017 at 10:42:41AM +0000, Peter Maydell wrote:
> 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...
>

I'm pretty sure we need the nasty hack, but I'm also Ccing David for
his opinion.

Thanks,
drew