Re: [PATCH] hw/block: m25p80: Fix fast read for SST flashes

[Francisco Iglesias <frasse.iglesias@gmail.com>]

Hi Bin and Alistair,

On [2020 Dec 02] Wed 11:40:11, Alistair Francis wrote:
> On Sun, Nov 29, 2020 at 6:55 PM Bin Meng <bmeng.cn@gmail.com> wrote:
> >
> > From: Bin Meng <bin.meng@windriver.com>
> >
> > SST flashes require a dummy byte after the address bits.
> >
> > Signed-off-by: Bin Meng <bin.meng@windriver.com>
> 
> I couldn't find a datasheet that says this... But the actual code
> change looks fine, so:
> 
> Acked-by: Alistair Francis <alistair.francis@wdc.com>
> 
> Alistair
> 
> > ---
> >
> >  hw/block/m25p80.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
> > index 483925f..9b36762 100644
> > --- a/hw/block/m25p80.c
> > +++ b/hw/block/m25p80.c
> > @@ -825,6 +825,9 @@ static void decode_fast_read_cmd(Flash *s)
> >      s->needed_bytes = get_addr_length(s);
> >      switch (get_man(s)) {
> >      /* Dummy cycles - modeled with bytes writes instead of bits */
> > +    case MAN_SST:
> > +        s->needed_bytes += 1;

1 dummy clk cycle is modelled as 1 byte write (see the comment above), so 1
dummy byte (8 dummy clk cycles) will need +8 above. An option could be to fall
through to the Windbond case below instead (since it seems to operate
likewise). 

Best regards,
Francisco Iglesias


> > +        break;
> >      case MAN_WINBOND:
> >          s->needed_bytes += 8;
> >          break;
> > --
> > 2.7.4
> >
> >
>