Re: [PATCH 3/3] MTD: spi-nor: add flag to not use sector erase.

[Marek Vasut]

On Monday, May 04, 2015 at 03:18:56 PM, Michal Suchanek wrote:
> On 4 May 2015 at 14:12, Marek Vasut <marex@xxxxxxx> wrote:
> > On Monday, May 04, 2015 at 01:11:03 PM, Michal Suchanek wrote:
> >> Hello,
> > 
> > Hi!
> > 
> >> On 1 May 2015 at 16:20, Marek Vasut <marex@xxxxxxx> wrote:
> >> > On Friday, May 01, 2015 at 09:05:15 AM, Michal Suchanek wrote:
> >> >> On 1 May 2015 at 01:13, Marek Vasut <marex@xxxxxxx> wrote:
> >> >> I can determine it for this particular chip. However, when the vendor
> >> >> datasheet says the block is 64/32K it might mean that chips with this
> >> >> ID can have either block size.
> >> > 
> >> > http://www.chingistek.com/img/Product_Files/Pm25LD010020datasheet%20v0
> >> > 4.p df page 21:
> >> > 
> >> > SECTOR_ER (20h) erases 4kByte sector.
> >> > BLOCK_ER (d8h) erases 64kByte sector.
> >> > 
> >> > http://www.gigadevice.com/product/download/366.html?locale=en_US
> >> > page 27-28:
> >> > 
> >> > Sector Erase (SE) (20h) erases 4kByte sector
> >> > 64KB Block Erase (BE) (d8h) erases 64kByte sector
> >> 
> >> It's pretty much the same as the datasheet I used
> >> http://www.elm-tech.com/en/products/spi-flash-memory/gd25q41/gd25q41.pdf
> >> 
> >> It mentions both
> >> 32KB Block Erase (BE) (52H)
> >> and
> >> 64KB Block Erase (BE) (D8H)
> > 
> > The SPI NOR framework will use 0xbe opcode, no problem.
> > 
> >> So the chip probably tries its best to be compatible with any command
> >> set and this last patch is not needed. The memory organization table
> >> on page 7 is not all that reassuring, though.
> > 
> > Which exact part do you refer to please ?
> 
> Start of page 7 where it says sector size 32/64K in either datasheet.
> 
> It can refer to both BE opcode variants being supported but it's quite
> unclear.

My guess here would be that the internal organisation of the SPI NOR is
in 4k blocks, which is no surprise really. My understanding is that opcode
0x52 erases 8x4k sector (ie. 32k of data) while 0xd8 erases 16x4k sector
(ie. 64k of data). I don't see any problem here -- there are two different 
opcodes which do two different things and their behavior matches the one on 
various other SPI NORs.

> Write protection seems to be calculated in 4k sectors and not blocks
> so the block size does not seem very relevant.

See above. Does it make sense now please ?

Best regards,
Marek Vasut
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