[PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

[PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

[Shaik Sajida Bhanu]

Add support for winbond W25Q512NW-IM chip.

Signed-off-by: Shaik Sajida Bhanu <quic_c_sbhanu@quicinc.com>
Reviewed-by: Doug Anderson <dianders@chromium.org>
---

Changes since V1:
	- Added space before name of the flash part as suggested by Doug.

Changes since V2:
	- Updated chip name as w25q512nwm as suggested by Doug.

Changes since V3:
	- Updated flash_info flags passing according to below patch
	 https://lore.kernel.org/all/20211207140254.87681-7-tudor.ambarus@microchip.com/
	 As suggested by Tudor Ambarus.
---
 drivers/mtd/spi-nor/winbond.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/mtd/spi-nor/winbond.c b/drivers/mtd/spi-nor/winbond.c
index 675f32c..c4be225 100644
--- a/drivers/mtd/spi-nor/winbond.c
+++ b/drivers/mtd/spi-nor/winbond.c
@@ -124,6 +124,10 @@ static const struct flash_info winbond_parts[] = {
 	{ "w25m512jv", INFO(0xef7119, 0, 64 * 1024, 1024)
 		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_QUAD_READ |
 			      SPI_NOR_DUAL_READ) },
+	{ "w25q512nwm", INFO(0xef8020, 0, 64 * 1024, 1024)
+		FLAGS(SPI_NOR_HAS_LOCK | SPI_NOR_HAS_TB)
+		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_DUAL_READ |
+			      SPI_NOR_QUAD_READ) },
 	{ "w25q512jvq", INFO(0xef4020, 0, 64 * 1024, 1024)
 		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_DUAL_READ |
 			      SPI_NOR_QUAD_READ) },
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member 
of Code Aurora Forum, hosted by The Linux Foundation

Re: [PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

[Pratyush Yadav]

Hi,

On 20/01/22 03:24PM, Shaik Sajida Bhanu wrote:
> Add support for winbond W25Q512NW-IM chip.
> 
> Signed-off-by: Shaik Sajida Bhanu <quic_c_sbhanu@quicinc.com>
> Reviewed-by: Doug Anderson <dianders@chromium.org>
> ---
> 
> Changes since V1:
> 	- Added space before name of the flash part as suggested by Doug.
> 
> Changes since V2:
> 	- Updated chip name as w25q512nwm as suggested by Doug.
> 
> Changes since V3:
> 	- Updated flash_info flags passing according to below patch
> 	 https://lore.kernel.org/all/20211207140254.87681-7-tudor.ambarus@microchip.com/
> 	 As suggested by Tudor Ambarus.
> ---
>  drivers/mtd/spi-nor/winbond.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/winbond.c b/drivers/mtd/spi-nor/winbond.c
> index 675f32c..c4be225 100644
> --- a/drivers/mtd/spi-nor/winbond.c
> +++ b/drivers/mtd/spi-nor/winbond.c
> @@ -124,6 +124,10 @@ static const struct flash_info winbond_parts[] = {
>  	{ "w25m512jv", INFO(0xef7119, 0, 64 * 1024, 1024)
>  		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_QUAD_READ |
>  			      SPI_NOR_DUAL_READ) },
> +	{ "w25q512nwm", INFO(0xef8020, 0, 64 * 1024, 1024)
> +		FLAGS(SPI_NOR_HAS_LOCK | SPI_NOR_HAS_TB)
> +		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_DUAL_READ |
> +			      SPI_NOR_QUAD_READ) },

This way is for "legacy" flash code and is not recommended anymore. Does 
the flash support SFDP? In that case just add PARSE_SFDP and let the 
SFDP parser discover these capabilities. You can keep the "FLAGS" part 
since those are not discoverable via SFDP.

>  	{ "w25q512jvq", INFO(0xef4020, 0, 64 * 1024, 1024)
>  		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_DUAL_READ |
>  			      SPI_NOR_QUAD_READ) },
> -- 
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member 
> of Code Aurora Forum, hosted by The Linux Foundation
> 

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.

Re: [PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

[Michael Walle]

Hi,

Am 2022-01-20 10:54, schrieb Shaik Sajida Bhanu:
> Add support for winbond W25Q512NW-IM chip.
> 
> Signed-off-by: Shaik Sajida Bhanu <quic_c_sbhanu@quicinc.com>
> Reviewed-by: Doug Anderson <dianders@chromium.org>
> ---
> 
> Changes since V1:
> 	- Added space before name of the flash part as suggested by Doug.
> 
> Changes since V2:
> 	- Updated chip name as w25q512nwm as suggested by Doug.
> 
> Changes since V3:
> 	- Updated flash_info flags passing according to below patch

Thanks!

Please note, that you also have to supply a SFDP dump, see [1].

> https://lore.kernel.org/all/20211207140254.87681-7-tudor.ambarus@microchip.com/
> 	 As suggested by Tudor Ambarus.
> ---
>  drivers/mtd/spi-nor/winbond.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/winbond.c 
> b/drivers/mtd/spi-nor/winbond.c
> index 675f32c..c4be225 100644
> --- a/drivers/mtd/spi-nor/winbond.c
> +++ b/drivers/mtd/spi-nor/winbond.c
> @@ -124,6 +124,10 @@ static const struct flash_info winbond_parts[] = {
>  	{ "w25m512jv", INFO(0xef7119, 0, 64 * 1024, 1024)
>  		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_QUAD_READ |
>  			      SPI_NOR_DUAL_READ) },
> +	{ "w25q512nwm", INFO(0xef8020, 0, 64 * 1024, 1024)
> +		FLAGS(SPI_NOR_HAS_LOCK | SPI_NOR_HAS_TB)
> +		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_DUAL_READ |
> +			      SPI_NOR_QUAD_READ) },

Could you try adding OTP_INFO(256, 3, 0x1000, 0x1000), this
should enable OTP support. Could you please test this using the
flash_otp_{dump,info,erase,write} tools and add that line?

I've checked ID duplications, because there is the w25qNNjw
series. There doesn't seem to exist a w25q512jw, so we are
safe for now. There is only a w25q512jv and it has the id
0xef4020.

fun fact.. the w25q512nwm describes the OTP lock bit for
the first OTP region (the one which is not documented and
I've found out that its used for storing the SFDP) as
SFDP lock bit. See ch "7.1.1 Security Register Lock Bits
(LB3, LB2, LB1, SFDP Lock bit)". So we finally have
evidence :)

-michael

[1] 
https://lore.kernel.org/linux-mtd/4304e19f3399a0a6e856119d01ccabe0@walle.cc/

RE: [PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

[Sajida Bhanu (Temp) (QUIC)]

Hi,

Thanks for the review.

Please find the inline comments.

Thanks,
Sajida

-----Original Message-----
From: Pratyush Yadav <p.yadav@ti.com> 
Sent: Thursday, January 20, 2022 3:42 PM
To: Sajida Bhanu (Temp) (QUIC) <quic_c_sbhanu@quicinc.com>
Cc: dianders@chromium.org; tudor.ambarus@microchip.com; michael@walle.cc; miquel.raynal@bootlin.com; richard@nod.at; vigneshr@ti.com; linux-mtd@lists.infradead.org; linux-kernel@vger.kernel.org; stummala@codeaurora.org; vbadigan@codeaurora.org; Ram Prakash Gupta (QUIC) <quic_rampraka@quicinc.com>; Pradeep Pragallapati (QUIC) <quic_pragalla@quicinc.com>; sartgarg@codeaurora.org
Subject: Re: [PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

Hi,

On 20/01/22 03:24PM, Shaik Sajida Bhanu wrote:
> Add support for winbond W25Q512NW-IM chip.
> 
> Signed-off-by: Shaik Sajida Bhanu <quic_c_sbhanu@quicinc.com>
> Reviewed-by: Doug Anderson <dianders@chromium.org>
> ---
> 
> Changes since V1:
> 	- Added space before name of the flash part as suggested by Doug.
> 
> Changes since V2:
> 	- Updated chip name as w25q512nwm as suggested by Doug.
> 
> Changes since V3:
> 	- Updated flash_info flags passing according to below patch
> 	 https://lore.kernel.org/all/20211207140254.87681-7-tudor.ambarus@microchip.com/
> 	 As suggested by Tudor Ambarus.
> ---
>  drivers/mtd/spi-nor/winbond.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/winbond.c 
> b/drivers/mtd/spi-nor/winbond.c index 675f32c..c4be225 100644
> --- a/drivers/mtd/spi-nor/winbond.c
> +++ b/drivers/mtd/spi-nor/winbond.c
> @@ -124,6 +124,10 @@ static const struct flash_info winbond_parts[] = {
>  	{ "w25m512jv", INFO(0xef7119, 0, 64 * 1024, 1024)
>  		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_QUAD_READ |
>  			      SPI_NOR_DUAL_READ) },
> +	{ "w25q512nwm", INFO(0xef8020, 0, 64 * 1024, 1024)
> +		FLAGS(SPI_NOR_HAS_LOCK | SPI_NOR_HAS_TB)
> +		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_DUAL_READ |
> +			      SPI_NOR_QUAD_READ) },

This way is for "legacy" flash code and is not recommended anymore. Does the flash support SFDP? In that case just add PARSE_SFDP and let the SFDP parser discover these capabilities. You can keep the "FLAGS" part since those are not discoverable via SFDP.

>>>>>>>Yes this flash supports SFDP, sure will pass PARSE_SFDP.

>  	{ "w25q512jvq", INFO(0xef4020, 0, 64 * 1024, 1024)
>  		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_DUAL_READ |
>  			      SPI_NOR_QUAD_READ) },
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a 
> member of Code Aurora Forum, hosted by The Linux Foundation
> 

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.

RE: [PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

[Sajida Bhanu (Temp) (QUIC)]

-----Original Message-----
From: Michael Walle <michael@walle.cc> 
Sent: Thursday, January 20, 2022 4:02 PM
To: Sajida Bhanu (Temp) (QUIC) <quic_c_sbhanu@quicinc.com>
Cc: dianders@chromium.org; tudor.ambarus@microchip.com; p.yadav@ti.com; miquel.raynal@bootlin.com; richard@nod.at; vigneshr@ti.com; linux-mtd@lists.infradead.org; linux-kernel@vger.kernel.org; stummala@codeaurora.org; vbadigan@codeaurora.org; Ram Prakash Gupta (QUIC) <quic_rampraka@quicinc.com>; Pradeep Pragallapati (QUIC) <quic_pragalla@quicinc.com>; sartgarg@codeaurora.org
Subject: Re: [PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

Hi,

Am 2022-01-20 10:54, schrieb Shaik Sajida Bhanu:
> Add support for winbond W25Q512NW-IM chip.
> 
> Signed-off-by: Shaik Sajida Bhanu <quic_c_sbhanu@quicinc.com>
> Reviewed-by: Doug Anderson <dianders@chromium.org>
> ---
> 
> Changes since V1:
> 	- Added space before name of the flash part as suggested by Doug.
> 
> Changes since V2:
> 	- Updated chip name as w25q512nwm as suggested by Doug.
> 
> Changes since V3:
> 	- Updated flash_info flags passing according to below patch

Thanks!

Please note, that you also have to supply a SFDP dump, see [1].

> https://lore.kernel.org/all/20211207140254.87681-7-tudor.ambarus@microchip.com/
> 	 As suggested by Tudor Ambarus.
> ---
>  drivers/mtd/spi-nor/winbond.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/winbond.c 
> b/drivers/mtd/spi-nor/winbond.c index 675f32c..c4be225 100644
> --- a/drivers/mtd/spi-nor/winbond.c
> +++ b/drivers/mtd/spi-nor/winbond.c
> @@ -124,6 +124,10 @@ static const struct flash_info winbond_parts[] = {
>  	{ "w25m512jv", INFO(0xef7119, 0, 64 * 1024, 1024)
>  		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_QUAD_READ |
>  			      SPI_NOR_DUAL_READ) },
> +	{ "w25q512nwm", INFO(0xef8020, 0, 64 * 1024, 1024)
> +		FLAGS(SPI_NOR_HAS_LOCK | SPI_NOR_HAS_TB)
> +		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_DUAL_READ |
> +			      SPI_NOR_QUAD_READ) },

Could you try adding OTP_INFO(256, 3, 0x1000, 0x1000), this should enable OTP support. Could you please test this using the flash_otp_{dump,info,erase,write} tools and add that line?

I've checked ID duplications, because there is the w25qNNjw series. There doesn't seem to exist a w25q512jw, so we are safe for now. There is only a w25q512jv and it has the id 0xef4020.

fun fact.. the w25q512nwm describes the OTP lock bit for the first OTP region (the one which is not documented and I've found out that its used for storing the SFDP) as SFDP lock bit. See ch "7.1.1 Security Register Lock Bits (LB3, LB2, LB1, SFDP Lock bit)". So we finally have evidence :)

-michael

Hi,

Thanks for the review.. 

Can you please share the documentation about OTP_INFO settings(Advantages etc..) if any.

Can you please share more info on  flash_otp_{dump,info,erase,write} tools.

Thanks,
Sajida

[1]
https://lore.kernel.org/linux-mtd/4304e19f3399a0a6e856119d01ccabe0@walle.cc/

Re: [PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

[Michael Walle]

Hi,

Am 2022-01-25 16:36, schrieb Sajida Bhanu (Temp) (QUIC):
> Am 2022-01-20 10:54, schrieb Shaik Sajida Bhanu:
>> Add support for winbond W25Q512NW-IM chip.
>> 
>> Signed-off-by: Shaik Sajida Bhanu <quic_c_sbhanu@quicinc.com>
>> Reviewed-by: Doug Anderson <dianders@chromium.org>
>> ---
>> 
>> Changes since V1:
>> 	- Added space before name of the flash part as suggested by Doug.
>> 
>> Changes since V2:
>> 	- Updated chip name as w25q512nwm as suggested by Doug.
>> 
>> Changes since V3:
>> 	- Updated flash_info flags passing according to below patch
> 
> Thanks!
> 
> Please note, that you also have to supply a SFDP dump, see [1].
> 
>> https://lore.kernel.org/all/20211207140254.87681-7-tudor.ambarus@microchip.com/
>> 	 As suggested by Tudor Ambarus.
>> ---
>>  drivers/mtd/spi-nor/winbond.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>> 
>> diff --git a/drivers/mtd/spi-nor/winbond.c
>> b/drivers/mtd/spi-nor/winbond.c index 675f32c..c4be225 100644
>> --- a/drivers/mtd/spi-nor/winbond.c
>> +++ b/drivers/mtd/spi-nor/winbond.c
>> @@ -124,6 +124,10 @@ static const struct flash_info winbond_parts[] = 
>> {
>>  	{ "w25m512jv", INFO(0xef7119, 0, 64 * 1024, 1024)
>>  		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_QUAD_READ |
>>  			      SPI_NOR_DUAL_READ) },
>> +	{ "w25q512nwm", INFO(0xef8020, 0, 64 * 1024, 1024)
>> +		FLAGS(SPI_NOR_HAS_LOCK | SPI_NOR_HAS_TB)
>> +		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_DUAL_READ |
>> +			      SPI_NOR_QUAD_READ) },
> 
> Could you try adding OTP_INFO(256, 3, 0x1000, 0x1000), this should
> enable OTP support. Could you please test this using the
> flash_otp_{dump,info,erase,write} tools and add that line?
> 
> I've checked ID duplications, because there is the w25qNNjw series.
> There doesn't seem to exist a w25q512jw, so we are safe for now. There
> is only a w25q512jv and it has the id 0xef4020.
> 
> fun fact.. the w25q512nwm describes the OTP lock bit for the first OTP
> region (the one which is not documented and I've found out that its
> used for storing the SFDP) as SFDP lock bit. See ch "7.1.1 Security
> Register Lock Bits (LB3, LB2, LB1, SFDP Lock bit)". So we finally have
> evidence :)
> 
> -michael
> 
> Hi,
> 
> Thanks for the review..
> 
> Can you please share the documentation about OTP_INFO
> settings(Advantages etc..) if any.

I would like to see support for OTP right from the start, and
because you have that specific flash chip, you are in the position
to test it :)

With this line (it should already be exact that line I provided,
I checked the datasheet), you just enable access to a seperate
OTP memory inside that flash. The datasheet calls them Security
Registers, you can have a look there.

> Can you please share more info on
> flash_otp_{dump,info,erase,write} tools.

What do you mean? You can find these tools in the mtd-utils
package or at http://www.linux-mtd.infradead.org/ (couldn't check,
website seems to be down for me at least).

You should make sure to have the latest version, which has a
bugfix for the flash_otp_dump and only newer versions have the
flash_otp_erase tool.

Examples:

# flash_otp_dump -u /dev/mtd0 0
OTP user data for /dev/mtd0
0x0000: 56 01 55 53 44 30 47 30 30 30 32 00 00 00 00 00
0x0010: 00 00 a0 a5 5c 6b 62 7b ff ff ff ff ff ff ff ff
0x0020: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
0x0030: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
0x0040: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[..]

# flash_otp_info -u /dev/mtd0
Number of OTP user blocks on /dev/mtd0: 3
block  0:  offset = 0x0000  size = 256 bytes  [locked]
block  1:  offset = 0x0100  size = 256 bytes  [unlocked]
block  2:  offset = 0x0200  size = 256 bytes  [unlocked]

# echo -n hello world | flash_otp_write -u /dev/mtd0 0x100
Writing OTP user data on /dev/mtd0 at offset 0x100
Wrote 11 bytes of OTP user data

# flash_otp_dump -u /dev/mtd0 0x100
OTP user data for /dev/mtd0
0x0100: 68 65 6c 6c 6f 20 77 6f 72 6c 64 ff ff ff ff ff
0x0110: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
0x0120: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[..]

# flash_otp_erase -u /dev/mtd0 0x100 0x200
# flash_otp_dump -u /dev/mtd0 0x100
OTP user data for /dev/mtd0
0x0100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
0x0110: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
0x0120: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[..]

For completeness, there is also flash_otp_lock, but that
is not reversible and you'd lock the OTP area forever.

HTH,
-michael

RE: [PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

[Sajida Bhanu (Temp) (QUIC)]

HI,

Sure thanks for the info .. will add the change and test it.

Thanks,
Sajida
-----Original Message-----
From: Michael Walle <michael@walle.cc> 
Sent: Tuesday, January 25, 2022 9:23 PM
To: Sajida Bhanu (Temp) (QUIC) <quic_c_sbhanu@quicinc.com>
Cc: dianders@chromium.org; tudor.ambarus@microchip.com; p.yadav@ti.com; miquel.raynal@bootlin.com; richard@nod.at; vigneshr@ti.com; linux-mtd@lists.infradead.org; linux-kernel@vger.kernel.org; stummala@codeaurora.org; vbadigan@codeaurora.org; Ram Prakash Gupta (QUIC) <quic_rampraka@quicinc.com>; Pradeep Pragallapati (QUIC) <quic_pragalla@quicinc.com>; sartgarg@codeaurora.org
Subject: Re: [PATCH V4] mtd: spi-nor: winbond: Add support for winbond chip

Hi,

Am 2022-01-25 16:36, schrieb Sajida Bhanu (Temp) (QUIC):
> Am 2022-01-20 10:54, schrieb Shaik Sajida Bhanu:
>> Add support for winbond W25Q512NW-IM chip.
>> 
>> Signed-off-by: Shaik Sajida Bhanu <quic_c_sbhanu@quicinc.com>
>> Reviewed-by: Doug Anderson <dianders@chromium.org>
>> ---
>> 
>> Changes since V1:
>> 	- Added space before name of the flash part as suggested by Doug.
>> 
>> Changes since V2:
>> 	- Updated chip name as w25q512nwm as suggested by Doug.
>> 
>> Changes since V3:
>> 	- Updated flash_info flags passing according to below patch
> 
> Thanks!
> 
> Please note, that you also have to supply a SFDP dump, see [1].
> 
>> https://lore.kernel.org/all/20211207140254.87681-7-tudor.ambarus@microchip.com/
>> 	 As suggested by Tudor Ambarus.
>> ---
>>  drivers/mtd/spi-nor/winbond.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>> 
>> diff --git a/drivers/mtd/spi-nor/winbond.c 
>> b/drivers/mtd/spi-nor/winbond.c index 675f32c..c4be225 100644
>> --- a/drivers/mtd/spi-nor/winbond.c
>> +++ b/drivers/mtd/spi-nor/winbond.c
>> @@ -124,6 +124,10 @@ static const struct flash_info winbond_parts[] = 
>> {
>>  	{ "w25m512jv", INFO(0xef7119, 0, 64 * 1024, 1024)
>>  		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_QUAD_READ |
>>  			      SPI_NOR_DUAL_READ) },
>> +	{ "w25q512nwm", INFO(0xef8020, 0, 64 * 1024, 1024)
>> +		FLAGS(SPI_NOR_HAS_LOCK | SPI_NOR_HAS_TB)
>> +		NO_SFDP_FLAGS(SECT_4K | SPI_NOR_DUAL_READ |
>> +			      SPI_NOR_QUAD_READ) },
> 
> Could you try adding OTP_INFO(256, 3, 0x1000, 0x1000), this should 
> enable OTP support. Could you please test this using the 
> flash_otp_{dump,info,erase,write} tools and add that line?
> 
> I've checked ID duplications, because there is the w25qNNjw series.
> There doesn't seem to exist a w25q512jw, so we are safe for now. There 
> is only a w25q512jv and it has the id 0xef4020.
> 
> fun fact.. the w25q512nwm describes the OTP lock bit for the first OTP 
> region (the one which is not documented and I've found out that its 
> used for storing the SFDP) as SFDP lock bit. See ch "7.1.1 Security 
> Register Lock Bits (LB3, LB2, LB1, SFDP Lock bit)". So we finally have 
> evidence :)
> 
> -michael
> 
> Hi,
> 
> Thanks for the review..
> 
> Can you please share the documentation about OTP_INFO 
> settings(Advantages etc..) if any.

I would like to see support for OTP right from the start, and because you have that specific flash chip, you are in the position to test it :)

With this line (it should already be exact that line I provided, I checked the datasheet), you just enable access to a seperate OTP memory inside that flash. The datasheet calls them Security Registers, you can have a look there.

> Can you please share more info on
> flash_otp_{dump,info,erase,write} tools.

What do you mean? You can find these tools in the mtd-utils package or at http://www.linux-mtd.infradead.org/ (couldn't check, website seems to be down for me at least).

You should make sure to have the latest version, which has a bugfix for the flash_otp_dump and only newer versions have the flash_otp_erase tool.

Examples:

# flash_otp_dump -u /dev/mtd0 0
OTP user data for /dev/mtd0
0x0000: 56 01 55 53 44 30 47 30 30 30 32 00 00 00 00 00
0x0010: 00 00 a0 a5 5c 6b 62 7b ff ff ff ff ff ff ff ff
0x0020: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
0x0030: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
0x0040: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff [..]

# flash_otp_info -u /dev/mtd0
Number of OTP user blocks on /dev/mtd0: 3 block  0:  offset = 0x0000  size = 256 bytes  [locked] block  1:  offset = 0x0100  size = 256 bytes  [unlocked] block  2:  offset = 0x0200  size = 256 bytes  [unlocked]

# echo -n hello world | flash_otp_write -u /dev/mtd0 0x100 Writing OTP user data on /dev/mtd0 at offset 0x100 Wrote 11 bytes of OTP user data

# flash_otp_dump -u /dev/mtd0 0x100
OTP user data for /dev/mtd0
0x0100: 68 65 6c 6c 6f 20 77 6f 72 6c 64 ff ff ff ff ff
0x0110: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
0x0120: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff [..]

# flash_otp_erase -u /dev/mtd0 0x100 0x200 # flash_otp_dump -u /dev/mtd0 0x100 OTP user data for /dev/mtd0
0x0100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
0x0110: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
0x0120: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff [..]

For completeness, there is also flash_otp_lock, but that is not reversible and you'd lock the OTP area forever.

HTH,
-michael