Re: flash_lock issue for n25q 128mb spi nor part

[John Garry <john.garry@huawei.com>]

On 03/12/2019 12:35, John Garry wrote:
> On 03/12/2019 12:27, Tudor.Ambarus@microchip.com wrote:
>>
>>
>> On 12/3/19 2:05 PM, Tudor.Ambarus@microchip.com wrote:
>>> diff --git a/drivers/mtd/spi-nor/spi-nor.c 
>>> b/drivers/mtd/spi-nor/spi-nor.c
>>> index f4afe123e9dc..f1490c7b5cb9 100644
>>> --- a/drivers/mtd/spi-nor/spi-nor.c
>>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>>> @@ -1033,10 +1033,19 @@ static int 
>>> spi_nor_write_16bit_sr_and_check(struct spi_nor *nor, u8 sr1)
>>>
>>>          sr_cr[0] = sr1;
>>>
>>> +       dev_err(nor->dev, "before write: sr_cr[0] = %02x, sr_cr[1] = 
>>> %02x\n",
>>> +               sr_cr[0], sr_cr[1]);
>>> +
>>>          ret = spi_nor_write_sr(nor, sr_cr, 2);
>>>          if (ret)
>>>                  return ret;
>>>
>>> +       ret = spi_nor_read_sr(nor, &sr_cr[0]);
>>> +       if (ret)
>>> +               return ret;
>>> +
>>> +       dev_err(nor->dev, "read back sr1: sr_cr[0] = %02x\n", sr_cr[0]);
>>> +
>>>          if (nor->flags & SNOR_F_NO_READ_CR)
>>>                  return 0;
>>>
>>> @@ -1046,6 +1055,8 @@ static int 
>>> spi_nor_write_16bit_sr_and_check(struct spi_nor *nor, u8 sr1)
>>>          if (ret)
>>>                  return ret;
>>>
>>> +       dev_err(nor->dev, "read back sr2: sr_cr[1] = %02x\n", sr_cr[1]);
>>> +
>>>          if (cr_written != sr_cr[1]) {
>>>                  dev_dbg(nor->dev, "CR: read back test failed\
>>
>> On n25q256a I obtain:
>>
>> root@sama5d2-xplained-sd:~# flash_lock -l /dev/mtd1
>> spi-nor spi1.0: before write: sr_cr[0] = 9e, sr_cr[1] = ff
>> spi-nor spi1.0: read back sr1: sr_cr[0] = 02
>> spi-nor spi1.0: read back sr2: sr_cr[1] = ff
>>
> 
> So here is what I get:
> 
> root@ubuntu:/home/john# flash_lock -l /dev/mtd0
> [  109.037492] spi-nor spi-PRP0001:00: before write: sr_cr[0] = 9e, 
> sr_cr[1] = 00
> [  109.044769] spi-nor spi-PRP0001:00: read back sr1: sr_cr[0] = 02
> [  109.050790] spi-nor spi-PRP0001:00: read back sr2: sr_cr[1] = 00
> 
> 
>> the 16 bit write SR does not execute correctly and the WE remains set. If
>> neither of the micron flashes do not support the 16 bit write SR, we 
>> can add a
>> condition based on MFR. Let me check few datasheets.
>>
> 
> OK, thanks.

Hi Tudor,

Something else which I wanted to ask is why we don't check the FSR after 
a write command for that part?

Without it, if the flash is locked, a flash write reports no error, 
which could be maybe misleading.

A more real problem is that I find that SR.WEL is not cleared when we 
attempt to write when the flash is locked, and this causes issues when 
we attempt to reset the SR.

Here's an example flow (with my hack to stop using 16b SR method):

root@ubuntu:/home/john# flash_lock -l /dev/mtd0
root@ubuntu:/home/john# mtd_debug erase /dev/mtd0 0xe00000 4096
[   69.650642] spi-nor spi-PRP0001:00: at 0xe00000, len 4096
Erased 4096 bytes from address 0x00e00000 in flash
root@ubuntu:/home/john# mtd_debug write /dev/mtd0 0xe00000 4096 dump4096
[   77.093755] spi-nor spi-PRP0001:00: to 0x00e00000, len 4096
Copied 4096 bytes from dump4096 to address 0x00e00000 in flash
root@ubuntu:/home/john# mtd_debug read /dev/mtd0 0xe00000 4096 temp
[   82.162445] spi-nor spi-PRP0001:00: from 0x00e00000, len 4096
Copied 4096 bytes from address 0x00e00000 in flash to temp
root@ubuntu:/home/john# flash_lock -u /dev/mtd0
[   87.558435] spi-nor spi-PRP0001:00: SR1: read back test failed
flash_lock: error!: could not unlock device: /dev/mtd0

             error 5 (Input/output error)
root@ubuntu:/home/john#

Unlock reports an error as the the read back test in 
spi_nor_write_sr1_and_check() fails as the SR.WEL has never been cleared.

I'm just saying this while it's fresh in my head - I don't want to seem 
pushy :)

Thanks,
John

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/