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

[Takahiro Kuwano <tkuw584924@gmail.com>]

Hi Tudor,

I submitted another series about address mode discovery.
Please review that. I will revise this series after another one is settled.

Thanks,
Takahiro

On 8/8/2022 5:31 PM, Takahiro Kuwano wrote:
> On 8/8/2022 5:26 PM, Tudor.Ambarus@microchip.com wrote:
>> On 8/8/22 11:09, Takahiro Kuwano wrote:
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>
>>> On 8/8/2022 4:34 PM, Tudor.Ambarus@microchip.com wrote:
>>>> On 8/8/22 09:41, Takahiro Kuwano wrote:
>>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>>
>>>>> On 8/8/2022 3:08 PM, Tudor.Ambarus@microchip.com wrote:
>>>>>> On 8/8/22 08:42, Takahiro Kuwano wrote:
>>>>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>>>>
>>>>>>> On 8/8/2022 1:47 PM, Tudor.Ambarus@microchip.com wrote:
>>>>>>>> On 8/6/22 09:34, tkuw584924@gmail.com wrote:
>>>>>>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>>>>>>
>>>>>>>>> From: Takahiro Kuwano <Takahiro.Kuwano@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?
>>
> OK, I will prototype and test it.

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