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Date:   Thu, 26 Nov 2020 21:46:43 +0100
From:   Michael Walle <michael@...le.cc>
To:     Tudor.Ambarus@...rochip.com
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        miquel.raynal@...tlin.com, richard@....at, vigneshr@...com,
        boris.brezillon@...labora.com
Subject: Re: [PATCH v5 3/3] mtd: spi-nor: keep lock bits if they are
 non-volatile

Am 2020-11-25 19:52, schrieb Michael Walle:
> Am 2020-11-25 13:21, schrieb Tudor.Ambarus@...rochip.com:

[..]

>>> diff --git a/drivers/mtd/spi-nor/esmt.c b/drivers/mtd/spi-nor/esmt.c
>>> index c93170008118..c2ebf29d95f2 100644
>>> --- a/drivers/mtd/spi-nor/esmt.c
>>> +++ b/drivers/mtd/spi-nor/esmt.c
>>> @@ -11,9 +11,13 @@
>>>  static const struct flash_info esmt_parts[] = {
>>>         /* ESMT */
>>>         { "f25l32pa", INFO(0x8c2016, 0, 64 * 1024, 64,
>>> -                          SECT_4K | SPI_NOR_HAS_LOCK) },
>>> +                          SECT_4K | SPI_NOR_HAS_LOCK | 
>>> SPI_NOR_WP_IS_VOLATILE) },
>> 
>> https://www.esmt.com.tw/upload/pdf/ESMT/datasheets/F25L32PA.pdf
>> BP GENMASK(4,2), volatile, ok
>> 
>>>         { "f25l32qa", INFO(0x8c4116, 0, 64 * 1024, 64,
>>> -                          SECT_4K | SPI_NOR_HAS_LOCK) },
>>> +                          SECT_4K | SPI_NOR_HAS_LOCK | 
>>> SPI_NOR_WP_IS_VOLATILE) },
>> 
>> https://datasheetspdf.com/pdf-file/796196/ESMT/F25L32QA/1
>> Datasheet states that "BP0~3, QE and BPL bits are non-volatile."
>> At the same time, it says: "After power-up, BP3, BP2, BP1 and BP0 bits
>> are set to 0."
> 
> Mhh I had this datasheet:
> https://www.esmt.com.tw/upload/pdf/ESMT/datasheets/F25L32QA.pdf
> 
> In that one they are volatile.. but yours is a newer version. So I
> guess the flashes with the PA suffix have volatile BP and the QA ones
> have the non-volatile version.
> 
>> Maybe factory default setting for BPn is 0? Let's treat them as NV, as 
>> in
>> f25l64qa.
> 
> Yes will fix it.
> 
>> Do we need BP3?
> 
> Rather the top bottom bit. But that is outside of the scope of this 
> patch.
> And as per your rule, as I don't have this particular flash I cannot 
> test
> and thus couldn't add the TB bit (technically). But if you like I can 
> do
> another patch (outside of this series and after it is applied) which 
> will
> add the TB bit flag.

I've had a closer look at this. The top/bottom behavior is different
to that what we support in spi_nor_sr_lock(). But on the upside, the
current code is correct; it just doesn't support the TB bit. So we can
only protect addresses starting from the top. No changes needed here.

>> 
>>> +       /*
>>> +        * According to the datasheet the BPn bits are non-volatile, 
>>> whereas
>>> +        * they are volatile for the smaller f25l32qa.
>>> +        */
>>>         { "f25l64qa", INFO(0x8c4117, 0, 64 * 1024, 128,
>>>                            SECT_4K | SPI_NOR_HAS_LOCK) },
>> 
>> https://datasheetspdf.com/pdf-file/967488/EliteSemiconductor/F25L64QA/1
>> BP GENMASK(5, 2), non-volatile.
>> 
>> BP3?
> 
> Same as F25L32QA.

[..]

>>> diff --git a/drivers/mtd/spi-nor/sst.c b/drivers/mtd/spi-nor/sst.c
>>> index 8b169fa4102a..5e4450877d66 100644
>>> --- a/drivers/mtd/spi-nor/sst.c
>>> +++ b/drivers/mtd/spi-nor/sst.c
>>> @@ -11,26 +11,27 @@
>>>  static const struct flash_info sst_parts[] = {
>>>         /* SST -- large erase sizes are "overlays", "sectors" are 4K 
>>> */
>>>         { "sst25vf040b", INFO(0xbf258d, 0, 64 * 1024,  8,
>>> -                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK) 
>>> },
>>> +                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK 
>>> | SPI_NOR_WP_IS_VOLATILE) },
>>>         { "sst25vf080b", INFO(0xbf258e, 0, 64 * 1024, 16,
>>> -                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK) 
>>> },
>>> +                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK 
>>> | SPI_NOR_WP_IS_VOLATILE) },
>>>         { "sst25vf016b", INFO(0xbf2541, 0, 64 * 1024, 32,
>>> -                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK) 
>>> },
>>> +                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK 
>>> | SPI_NOR_WP_IS_VOLATILE) },
>>>         { "sst25vf032b", INFO(0xbf254a, 0, 64 * 1024, 64,
>>> -                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK) 
>>> },
>>> -       { "sst25vf064c", INFO(0xbf254b, 0, 64 * 1024, 128, SECT_4K | 
>>> SPI_NOR_HAS_LOCK) },
>>> +                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK 
>>> | SPI_NOR_WP_IS_VOLATILE) },
>>> +       { "sst25vf064c", INFO(0xbf254b, 0, 64 * 1024, 128,
>>> +                             SECT_4K | SPI_NOR_HAS_LOCK | 
>>> SPI_NOR_WP_IS_VOLATILE) },
>> 
>> Looks like BP3 is needed here.
> 
> https://ww1.microchip.com/downloads/en/DeviceDoc/20005036C.pdf
> 
> agreed. But again cannot test it. Would add it as a seperate patch
> to this series. (or leave it like it is)

I'll look at this tomorrow.

-michael

>> 
>>>         { "sst25wf512",  INFO(0xbf2501, 0, 64 * 1024,  1,
>>> -                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK) 
>>> },
>>> +                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK 
>>> | SPI_NOR_WP_IS_VOLATILE) },
>>>         { "sst25wf010",  INFO(0xbf2502, 0, 64 * 1024,  2,
>>> -                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK) 
>>> },
>>> +                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK 
>>> | SPI_NOR_WP_IS_VOLATILE) },
>>>         { "sst25wf020",  INFO(0xbf2503, 0, 64 * 1024,  4,
>>> -                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK) 
>>> },
>>> +                             SECT_4K | SST_WRITE | SPI_NOR_HAS_LOCK 
>>> | SPI_NOR_WP_IS_VOLATILE) },
>>>         { "sst25wf020a", INFO(0x621612, 0, 64 * 1024,  4, SECT_4K | 
>>> SPI_NOR_HAS_LOCK) },
>>>         { "sst25wf040b", INFO(0x621613, 0, 64 * 1024,  8, SECT_4K | 
>>> SPI_NOR_HAS_LOCK) },
>> 
>> These two flashes have just two BP bits located at bit 2 and 3.
>> Probably will work.
> 
> Mhh? What datasheet were you looking at? There are three BPs:
> https://ww1.microchip.com/downloads/en/DeviceDoc/SST25WF040B-4-Mbit-1.8V-SPI-Serial-Flash-Data-Sheet-DS20005193E.pdf
> 
> Ahh here are the tables which only inidicate two. But there are three.
> https://ww1.microchip.com/downloads/en/DeviceDoc/20005016C.pdf
> 
> And yes since the rework of the BP bits algorithm this should work
> as expected. Its just because the flash is too small to actually fill
> up all the BP bits.
> 
> -michael

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