[PATCH v4 0/3] add support for is25wp256 spi-nor device.

From: Sagar Shrikant Kadam
Date: Sat May 11 2019 - 06:09:53 EST

The patch set is tested on HiFive Unleashed board and is based on mainline
kernel v5.1. Its intended to add support for 32 MB spi-nor flash
mounted on the board. Memory Device supports 4/32/and 64 KB sectors size.
The device id table is updated accordingly.

Flash parameter table for ISSI device is set to use macronix_quad_enable
procedure to set the QE (quad-enable) bit of Status register.

A unilaterlay block unlocking scheme is added in patch 2.

These patches are based on original work done by Wesley Terpstra and/or Palmer Dabbelt:

Erase/Read/Write operations are verified on HiFive Unleashed board using mtd and flash utils (v1.5.2):
1. mtd_debug :Options available are : erase/read/write.
2. flashcp :Single utility that erases flash, writes a file to flash and verifies the data back.
3. flash_unlock: Unlock flash memory blocks.Arguments: are offset and number of blocks.
3. flash_lock: Lock flash memory blocks. Arguments: are offset and number of blocks.

Unlock scheme clears the protection bits of all blocks in the Status register.

Lock scheme:
A basic implementation based on stm_lock scheme and is validated for different number of blocks passed
to flash_lock. ISSI devices have Top/Bottom area selection in "function register" which is OTP memory.

Revision history:
-Extracted comman code and renamed few stm functions so that it can be reused for issi lock implementation.
-Added function's to read and write FR register, for selecting Top/Bottom area.

-Rebased patch to mainline v5.1 from earlier v5.1-rc5
-Updated commit messages, and cover letter with reference to git URL and author information.
-Deferred flash_lock mechanism and can go as separate patch.

V1<-> V2:
-Incorporated changes suggested by reviewers regarding patch/cover letter versioning, references of patch.
-Updated cover letter with description for flash operations verified with these changes.
-Add support for unlocking is25xxxxxx device
-Add support for locking is25xxxxxx device.

-Add support for is25wp256 device.

Sagar Shrikant Kadam (3):
mtd: spi-nor: add support for is25wp256
mtd: spi-nor: add support to unlock flash device.
mtd: spi-nor: add locking support for is25xxxxx device

drivers/mtd/spi-nor/spi-nor.c | 345 +++++++++++++++++++++++++++++++++++-------
include/linux/mtd/spi-nor.h | 7 +
2 files changed, 301 insertions(+), 51 deletions(-)