macronix ONFI nand flash OTP support

[Belisko Marek]

Hi Miquel,

On Thu, Nov 23, 2017 at 9:57 AM, Miquel RAYNAL
<miquel.raynal at free-electrons.com> wrote:
> Hi Marek,
>
> +CC: NAND maintainers Boris and Richard
>
>> Hi,
>>
>> I'm trying to add find out how to use OTP area in Macronix
>> MX30LF4G18AC flash. AFAIU it is ONFI based flash and I did some quick
>> hack and I can set/reset flash to go to OTP mode via get/set_features
>> function available in nand_base.c.
>
> Ok, so until now you can enter/leave OTP mode with get/set_features(),
> right ?
Yes exactly. Yesterday I make otp write/read working. Problem was that
otp pages for flash start at offset 0x2 up to 0x1f (at least mine
flash does have such range - 30 pages for otp).
>
>> But for read page I need to send
>> according datasheet:
>> To use the PAGE READ command for reading data from the OTP area, issue
>> the 00h command, and then issue five address cycles: for the first two
>> cycles, the column address; and for the remaining address cycles,
>> select a page in the range of 02h-00h-00h through 1Fh-00h-00h. Lastly,
>> issue the 30h command. The PAGE READ CACHE MODE command is not
>> supported on OTP pages.
>
> This is the description of a normal READ operation, there is nothing
> specific to OTP.
OH ok I did't see it in code I was looking at but from my above
comment it seems that it is because it's working :).
>
>>
>> I did check nand_do_read_ops function but it's not sending e.g. 0x30
>> which should be at the end of command. I'm using 4.1 kernel but
>> checked also 4.14 and no such functionality is added even there.
>> Nobody is using OTP area in nand flashes ;) ? Thanks for any pointers.
>
> I suppose you added some tweaks to enable OTP and use nand_do_read_ops,
> because there is currently no implementation for that in the NAND
> framework (I think there is something in MTD layer though). But must
> importantly, nand_do_read_ops basically calls chip->ecc.read*() which
> is handled by the controller driver, so what driver are you using ?
>
> How (where) did you trace the commands sent to the NAND chip ? For
> instance, if you just looked at the arguments of ->cmdfunc(), it is
> normal not to see any READSTART (0x30) command as it should be added
> automatically later in the function. If the driver implements
> ->cmd_ctrl(), you may see there what exactly is sent to the device.
Yes I checked ->cmdfunc() output. I think my changes would be
beneficial for other so I'll cook some patches and post for review
here.
>
> Thanks,
> Miquèl

thanks and BR,

marek

-- 
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-------------------------------------------------
Marek Belisko - OPEN-NANDRA
Freelance Developer

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