linux-kernel - Re: [RFC PATCH 1/2] mtd: spi-nor: atmel: remove global SNOR_F_HAS

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Message-ID: <137692b0-ab6d-b9be-17c2-68e3b3146076@microchip.com>
Date:   Thu, 1 Oct 2020 14:25:43 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <michael@...le.cc>
CC:     <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <miquel.raynal@...tlin.com>,
        <richard@....at>, <vigneshr@...com>
Subject: Re: [RFC PATCH 1/2] mtd: spi-nor: atmel: remove global
 SNOR_F_HAS_LOCK

On 10/1/20 5:12 PM, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Am 2020-10-01 16:06, schrieb Tudor.Ambarus@...rochip.com:
>> On 10/1/20 3:28 PM, Michael Walle wrote:
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know
>>> the content is safe
>>>
>>> This is considered bad for the following reasons:
>>>  (1) We only support the block protection with BPn bits for write
>>>      protection. Not all Atmel parts support this.
>>>  (2) Newly added flash chip will automatically inherit the "has
>>>      locking" support and thus needs to explicitly tested. Better
>>>      be opt-in instead of opt-out.
>>>  (3) There are already supported flashes which don't support the
>>> locking
>>>          scheme. So I assume this wasn't properly tested before adding
>>> that
>>>          chip; which enforces my previous argument that locking
>>> support should
>>>          be an opt-in.
>>>
>>> Remove the global flag and add individual flags to all flashes
>>> which supports BP locking. In particular the following flashes
>>> don't support the BP scheme:
>>>  - AT26F004
>>>  - AT25SL321
>>>  - AT45DB081D
>>>
>>> Signed-off-by: Michael Walle <michael@...le.cc>
>>> ---
>>>  drivers/mtd/spi-nor/atmel.c | 28 +++++++++-------------------
>>>  1 file changed, 9 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/drivers/mtd/spi-nor/atmel.c b/drivers/mtd/spi-nor/atmel.c
>>> index 3f5f21a473a6..49d392c6c8bc 100644
>>> --- a/drivers/mtd/spi-nor/atmel.c
>>> +++ b/drivers/mtd/spi-nor/atmel.c
>>> @@ -10,37 +10,27 @@
>>>
>>>  static const struct flash_info atmel_parts[] = {
>>>         /* Atmel -- some are (confusingly) marketed as "DataFlash" */
>>> -       { "at25fs010",  INFO(0x1f6601, 0, 32 * 1024,   4, SECT_4K) },
>>> -       { "at25fs040",  INFO(0x1f6604, 0, 64 * 1024,   8, SECT_4K) },
>>> +       { "at25fs010",  INFO(0x1f6601, 0, 32 * 1024,   4, SECT_4K |
>>> SPI_NOR_HAS_LOCK) },
>>> +       { "at25fs040",  INFO(0x1f6604, 0, 64 * 1024,   8, SECT_4K |
>>> SPI_NOR_HAS_LOCK) },
>>
>> after a quick look in the datasheets of these flashes, I suspect that
>> what we have now in the SPI NOR core for SR locking does not work for
>> them. They probably supported just "unlock all", clearing all the
>> BP bits. Anyway, different problem.
>>>
>>> -       { "at25df041a", INFO(0x1f4401, 0, 64 * 1024,   8, SECT_4K) },
>>> -       { "at25df321",  INFO(0x1f4700, 0, 64 * 1024,  64, SECT_4K) },
>>> -       { "at25df321a", INFO(0x1f4701, 0, 64 * 1024,  64, SECT_4K) },
>>> -       { "at25df641",  INFO(0x1f4800, 0, 64 * 1024, 128, SECT_4K) },
>>> +       { "at25df041a", INFO(0x1f4401, 0, 64 * 1024,   8, SECT_4K |
>>> SPI_NOR_HAS_LOCK) },
>>
>> this one does not support BP locking:
>> https://www.adestotech.com/wp-content/uploads/doc3668.pdf
>>
>>> +       { "at25df321",  INFO(0x1f4700, 0, 64 * 1024,  64, SECT_4K |
>>> SPI_NOR_HAS_LOCK) },
>>
>> neither this one:
>> https://datasheet.octopart.com/AT25DF321-S3U-Atmel-datasheet-8700896.pdf
>>
>>> +       { "at25df321a", INFO(0x1f4701, 0, 64 * 1024,  64, SECT_4K |
>>> SPI_NOR_HAS_LOCK) },
>>
>> nor this one: https://www.adestotech.com/wp-content/uploads/doc3686.pdf
>>
>>> +       { "at25df641",  INFO(0x1f4800, 0, 64 * 1024, 128, SECT_4K |
>>> SPI_NOR_HAS_LOCK) },
>>
>> nor this one: https://www.adestotech.com/wp-content/uploads/doc3680.pdf
>>
>> I stop here.
> 
> These are all the ones which use the global unlock. I cannot just skip
> the HAS_LOCK bit here, because otherwise this patch wouldn't be
> backwards
> compatibe. Yes I missed that in the commit log, my bad.
> 

No worries.

"unlock all at boot" just cleared the SR bits. Clearing the SR bits unlocks
these flashes?

Cheers,
ta