Re: [PATCH v3 2/3] mtd: spi-nor: add 4bit block protection support

[<Tudor.Ambarus@xxxxxxxxxxxxx>]

On Monday, February 10, 2020 2:14:48 PM EET Michael Walle wrote:
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> Am 2020-02-10 12:27, schrieb Tudor.Ambarus@xxxxxxxxxxxxx:
> > On Monday, February 10, 2020 12:40:59 PM EET Michael Walle wrote:
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> >> 
> >> Am 2020-02-10 10:59, schrieb Tudor.Ambarus@xxxxxxxxxxxxx:
> >> > On Monday, February 10, 2020 11:47:23 AM EET Tudor Ambarus wrote:
> >> >> > btw. we should catch the two special cases:
> >> >> > - lock none -> 0 (that was already the case)
> >> >> > - lock all -> all BP bits
> >> >> > 
> >> >> > The latter is important if "bp_slots_needed < bp_slots_available"
> >> >> > because there
> >> >> > are multiple settings for protect all. Most flashes will define any
> >> >> > remaining
> >> >> > setting for "protect all", but I've also seen flashes where the
> >> >> > in-between ones
> >> >> > were undefined (not mentioned) and only the "all bit set" was
> >> >> > protect
> >> >> > all.
> >> > 
> >> > I re-read this. Do you have such an example of flash? Aren't the BP
> >> > bits in
> >> > this case marked with "X", i.e. don't care? If not, probably we can
> >> > mask out
> >> > those undefined slots.
> >> 
> >> There was definetly some datasheet where the remaining ones wasn't
> >> described
> >> _and_ there was no X (don't care) bits. Unfortunately, I don't find it
> >> right
> >> now. That datasheed made me wonder what the other "undefinded" cases
> >> would be.
> >> Probably it will also be "protect all"; I just mentioned it because it
> >> would
> >> be an easy special case to handle. I don't think we should mask out
> >> anything,
> >> either use the slot in between (ie the one which the formula gives us)
> >> to
> >> protect all or use the largest setting (ie [TB3 |] TB2 | TB1 | TB0).
> >> And
> >> given the reasons above, I'd prefer the latter.
> > 
> > I'm fine with using the largest setting, but we'll need the proof
> > before going
> > this way.
> 
> have a look at 7.1.11:
>    https://www.winbond.com/resource-files/w25q80dv_revg_07212015.pdf
> 
> BP[2:0]=0b101 and 0b110 is not defined.
> 

Good enough for me. Thanks, Michael!




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