[PATCH 8/8] mtd: spi-nor: spansion: Add support for Infineon

[Tudor.Ambarus at microchip.com]

On 8/8/22 11:09, Takahiro Kuwano wrote:
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> On 8/8/2022 4:34 PM, Tudor.Ambarus at microchip.com wrote:
>> On 8/8/22 09:41, Takahiro Kuwano wrote:
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>>> On 8/8/2022 3:08 PM, Tudor.Ambarus at microchip.com wrote:
>>>> On 8/8/22 08:42, Takahiro Kuwano wrote:
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>>>>>
>>>>> On 8/8/2022 1:47 PM, Tudor.Ambarus at microchip.com wrote:
>>>>>> On 8/6/22 09:34, tkuw584924 at gmail.com wrote:
>>>>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>>>>
>>>>>>> From: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>
>>>>>>
>>>>>> Hi!
>>>>>>
>>>>>>>
>>>>>>> s25hl02gt and s25hs02gt
>>>>>>>
>>>>>>> Add ID, flags, and fixup for s25hl02gt and s25hs02gt.
>>>>>>> These parts are
>>>>>>>   - Dual-die package parts
>>>>>>>   - Not support chip erase
>>>>>>>   - 4-byte addressing mode by default
>>>>>>
>>>>>> CFR2N[7] CFR2V[7] says that: "For the DDP or QDP devices, if ADRBYT = 0
>>>>>> only the first 128 Mb of die 1 can be accessed."
>>>>>> So there are flashes of the same family that are by default in 3 byte address
>>>>>> mode. You added support just for a subset of them and used a generic name,
>>>>>> which is not accurate, right?
>>>>>>
>>>>> We added model #15 (3-byte address mode by default) to address special
>>>>> requirement from a customer who needs to use bootrom with 3-byte addressing.
>>>>> Anyway, I overlooked model # difference. Thanks for pointing out this.
>>>>>
>>>>>> Can we instead make an algorithm to determine the current address mode?
>>>>>>
>>>>> I have just found that we can distinguish model # via BFPT DWORD16.
>>>>> If Hardware reset, Software reset, or Power cycle can exit 4-byte address
>>>>> mode, that means the device is 3-byte address mode by default.
>>>>
>>>> I don't think this will help us. It doesn't matter the default mode if you
>>>> have a non volatile register that can be updated and changes the default
>>>> mode.
>>>>
>>>> Are there any registers/data that can be read successively in 3 byte addr mode
>>>> and then in 4 byte addr mode? We'll then compare what we receive from the flash
>>>> with a known value and determine the mode.
>>>>
>>> As we discussed before [0], if address mode in the controller and device are
>>
>> I remember, yes, but without determining the mode, the driver will work only
>> with flashes that come with the factory settings. The driver will be unusable
>> if someone changes the address mode in a non volatile way, right?
>>
> Yes, right.
> 
>>> different, the read data will be undetermined.
>>>
>>> But if we really want...
>>> Compare SR1 data read by RDSR1(05h - No Addr) and RDAR(65h - Addr 0).
>>> In most cases (without block protection), SR1=00h. The value of 00h would be
>>> awkward to determine if this is 'real' output from Flash or not. So, use> WREN(06h) and WRDI(04h) that flips BIT(1) in SR1.
>>
>> Would be good to have more fixed/OPT-like bits, or if we could change more bits
>> to increase the chances to not hit just some undetermined data.
>>>
>>> Therefore, something like:
>>> 1) RDSR1
>>> 2) RDAR with 3-byte addr (000000h)
>>> 3) If #1 == #2
>>>         4) WREN
>>>         5) RDAR with 3-byte addr (000000h)
>>>         6) BIT(1) is SR1==1?
>>>         ...
>>>
>>> Or simply WREN -> RDAR -> WRDI -> RDAR then check if only BIT(1) is toggled.
>>
>> Both may work, yes, but making the assumption on only one bit is fragile.
>> Can we use the Read Any Register Command with 3 and 4 byte address modes and
>> compare the values? Are there any registers with fixed values?
>>
> Register values can vary because it's register:)
> 
> So... let's use Data Integrity Check CRC registers. These registers do not
> have fixed values but we can calculate expected values by offline. Read
> several bytes (>=4) from Flash array with Read(03h) then calculate CRC by
> crc32(). Issue Data integrity Check command (5Bh) followed by start and
> end address (4-byte for each), wait till ready. Read calculated CRC by
> Read Any Register in 3 and 4 byte address (00800095h~0080098h) then compare
> the crc32() result and register read result.

Much better, yes. I think it is worth it. What's your opinion, Takahiro?
Others, Michael, Pratyush?

-- 
Cheers,
ta