linux-kernel - Re: [PATCH v2 2/2] mtd: spi-nor: sst: Add support for Global Unlock on sst26vf

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Message-ID: <8a0e7885-4b9e-be62-eb46-1af74c65afa8@microchip.com>
Date:   Wed, 20 Jan 2021 15:39:17 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <michael@...le.cc>
CC:     <vigneshr@...com>, <p.yadav@...com>, <miquel.raynal@...tlin.com>,
        <richard@....at>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <Kavyasree.Kotagiri@...rochip.com>
Subject: Re: [PATCH v2 2/2] mtd: spi-nor: sst: Add support for Global Unlock
 on sst26vf

On 1/20/21 5:02 PM, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Am 2021-01-20 15:52, schrieb Tudor.Ambarus@...rochip.com:
>> On 1/20/21 4:05 PM, Michael Walle wrote:
>>>> diff --git a/drivers/mtd/spi-nor/sst.c b/drivers/mtd/spi-nor/sst.c
>>>> index 00e48da0744a..d6e1396abb96 100644
>>>> --- a/drivers/mtd/spi-nor/sst.c
>>>> +++ b/drivers/mtd/spi-nor/sst.c
>>>> @@ -8,6 +8,39 @@
>>>>
>>>>  #include "core.h"
>>>>
>>>> +static int sst26vf_lock(struct spi_nor *nor, loff_t ofs, uint64_t
>>>> len)
>>>> +{
>>>> +     return -EOPNOTSUPP;
>>>> +}
>>>> +
>>>> +static int sst26vf_unlock(struct spi_nor *nor, loff_t ofs, uint64_t
>>>> len)
>>>> +{
>>>> +     if (ofs == 0 && len == nor->params->size)
>>>> +             return spi_nor_global_block_unlock(nor);
>>>
>>>
>>> Some blocks might not be unlocked because they are permanently
>>> locked. Does it make sense to read BPNV of the control register
>>> and add a debug message here?
>>
>> It would, yes. If any block is permanently locked in the unlock_all
>> case,
>> I'll just print a dbg message and return -EINVAL. Sounds good?
> 
> spi_nor_sr_unlock(), atmel_at25fs_unlock() and atmel_global_unprotect()
> will return -EIO in case the SR wasn't writable.

You mean in the spi_nor_write_sr_and_check() calls. -EIO is fine
there if what we wrote is different than what we read back, it would
indicate an IO error.

GBULK command clears all the write-protection bits in the Block
Protection register, except for those bits that have been permanently
locked down. So even if we have few blocks permanently locked, i.e.
CR.BPNV == 1, the GBULK can clear the protection for the remaining
blocks. So not really an IO error, but rather an -EINVAL, because
the user asks to unlock more than we can.

Cheers,
ta