linux/drivers/mtd/spi-nor/atmel.c
Michael Walle 31ad3eff09 mtd: spi-nor: keep lock bits if they are non-volatile
Traditionally, Linux unlocks the whole flash because there are legacy
devices which has the write protection bits set by default at startup.
If you actually want to use the flash protection bits, eg. because there
is a read-only part for a bootloader, this automatic unlocking is
harmful. If there is no hardware write protection in place (usually
called WP#), a startup of the kernel just discards this protection.

I've gone through the datasheets of all the flashes (except the Intel
ones where I could not find any datasheet nor reference) which supports
the unlocking feature and looked how the sector protection was
implemented. The currently supported flashes can be divided into the
following two categories:
 (1) block protection bits are non-volatile. Thus they keep their values
     at reset and power-cycle
 (2) flashes where these bits are volatile. After reset or power-cycle,
     the whole memory array is protected.
     (a) some devices needs a special "Global Unprotect" command, eg.
         the Atmel AT25DF041A.
     (b) some devices require to clear the BPn bits in the status
         register.

Due to the reasons above, we do not want to clear the bits for flashes
which belong to category (1). Fortunately for us, only Atmel flashes
fall into category (2a). Implement the "Global Protect" and "Global
Unprotect" commands for these. For (2b) we can use normal block
protection locking scheme.

This patch adds a new flag to indicate the case (2). Only if we have
such a flash we unlock the whole flash array. To be backwards compatible
it also introduces a kernel configuration option which restores the
complete legacy behavior ("Disable write protection on any flashes").
Hopefully, this will clean up "unlock the entire flash for legacy
devices" once and for all.

For reference here are the actually commits which introduced the legacy
behavior (and extended the behavior to other chip manufacturers):

commit f80e521c91 ("mtd: m25p80: add support for the Intel/Numonyx {16,32,64}0S33B SPI flash chips")
commit ea60658a08 ("mtd: m25p80: disable SST software protection bits by default")
commit 7228982442 ("[MTD] m25p80: fix bug - ATmel spi flash fails to be copied to")

Actually, this might also fix handling of the Atmel AT25DF flashes,
because the original commit 7228982442 ("[MTD] m25p80: fix bug -
ATmel spi flash fails to be copied to") was writing a 0 to the status
register, which is a "Global Unprotect". This might not be the case in
the current code which only handles the block protection bits BP2, BP1
and BP0. Thus, it depends on the current contents of the status register
if this unlock actually corresponds to a "Global Unprotect" command. In
the worst case, the current code might leave the AT25DF flashes in a
write protected state.

The commit 191f5c2ed4 ("mtd: spi-nor: use 16-bit WRR command when QE
is set on spansion flashes") changed that behavior by just clearing BP2
to BP0 instead of writing a 0 to the status register.

Further, the commit 3e0930f109 ("mtd: spi-nor: Rework the disabling
of block write protection") expanded the unlock_all() feature to ANY
flash which supports locking.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201203162959.29589-8-michael@walle.cc
2020-12-07 23:01:15 +05:30

200 lines
5.9 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2005, Intec Automation Inc.
* Copyright (C) 2014, Freescale Semiconductor, Inc.
*/
#include <linux/mtd/spi-nor.h>
#include "core.h"
#define ATMEL_SR_GLOBAL_PROTECT_MASK GENMASK(5, 2)
/*
* The Atmel AT25FS010/AT25FS040 parts have some weird configuration for the
* block protection bits. We don't support them. But legacy behavior in linux
* is to unlock the whole flash array on startup. Therefore, we have to support
* exactly this operation.
*/
static int atmel_at25fs_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
{
return -EOPNOTSUPP;
}
static int atmel_at25fs_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
{
int ret;
/* We only support unlocking the whole flash array */
if (ofs || len != nor->params->size)
return -EINVAL;
/* Write 0x00 to the status register to disable write protection */
ret = spi_nor_write_sr_and_check(nor, 0);
if (ret)
dev_dbg(nor->dev, "unable to clear BP bits, WP# asserted?\n");
return ret;
}
static int atmel_at25fs_is_locked(struct spi_nor *nor, loff_t ofs, uint64_t len)
{
return -EOPNOTSUPP;
}
static const struct spi_nor_locking_ops atmel_at25fs_locking_ops = {
.lock = atmel_at25fs_lock,
.unlock = atmel_at25fs_unlock,
.is_locked = atmel_at25fs_is_locked,
};
static void atmel_at25fs_default_init(struct spi_nor *nor)
{
nor->params->locking_ops = &atmel_at25fs_locking_ops;
}
static const struct spi_nor_fixups atmel_at25fs_fixups = {
.default_init = atmel_at25fs_default_init,
};
/**
* atmel_set_global_protection - Do a Global Protect or Unprotect command
* @nor: pointer to 'struct spi_nor'
* @ofs: offset in bytes
* @len: len in bytes
* @is_protect: if true do a Global Protect otherwise it is a Global Unprotect
*
* Return: 0 on success, -error otherwise.
*/
static int atmel_set_global_protection(struct spi_nor *nor, loff_t ofs,
uint64_t len, bool is_protect)
{
int ret;
u8 sr;
/* We only support locking the whole flash array */
if (ofs || len != nor->params->size)
return -EINVAL;
ret = spi_nor_read_sr(nor, nor->bouncebuf);
if (ret)
return ret;
sr = nor->bouncebuf[0];
/* SRWD bit needs to be cleared, otherwise the protection doesn't change */
if (sr & SR_SRWD) {
sr &= ~SR_SRWD;
ret = spi_nor_write_sr_and_check(nor, sr);
if (ret) {
dev_dbg(nor->dev, "unable to clear SRWD bit, WP# asserted?\n");
return ret;
}
}
if (is_protect) {
sr |= ATMEL_SR_GLOBAL_PROTECT_MASK;
/*
* Set the SRWD bit again as soon as we are protecting
* anything. This will ensure that the WP# pin is working
* correctly. By doing this we also behave the same as
* spi_nor_sr_lock(), which sets SRWD if any block protection
* is active.
*/
sr |= SR_SRWD;
} else {
sr &= ~ATMEL_SR_GLOBAL_PROTECT_MASK;
}
nor->bouncebuf[0] = sr;
/*
* We cannot use the spi_nor_write_sr_and_check() because this command
* isn't really setting any bits, instead it is an pseudo command for
* "Global Unprotect" or "Global Protect"
*/
return spi_nor_write_sr(nor, nor->bouncebuf, 1);
}
static int atmel_global_protect(struct spi_nor *nor, loff_t ofs, uint64_t len)
{
return atmel_set_global_protection(nor, ofs, len, true);
}
static int atmel_global_unprotect(struct spi_nor *nor, loff_t ofs, uint64_t len)
{
return atmel_set_global_protection(nor, ofs, len, false);
}
static int atmel_is_global_protected(struct spi_nor *nor, loff_t ofs, uint64_t len)
{
int ret;
if (ofs >= nor->params->size || (ofs + len) > nor->params->size)
return -EINVAL;
ret = spi_nor_read_sr(nor, nor->bouncebuf);
if (ret)
return ret;
return ((nor->bouncebuf[0] & ATMEL_SR_GLOBAL_PROTECT_MASK) == ATMEL_SR_GLOBAL_PROTECT_MASK);
}
static const struct spi_nor_locking_ops atmel_global_protection_ops = {
.lock = atmel_global_protect,
.unlock = atmel_global_unprotect,
.is_locked = atmel_is_global_protected,
};
static void atmel_global_protection_default_init(struct spi_nor *nor)
{
nor->params->locking_ops = &atmel_global_protection_ops;
}
static const struct spi_nor_fixups atmel_global_protection_fixups = {
.default_init = atmel_global_protection_default_init,
};
static const struct flash_info atmel_parts[] = {
/* Atmel -- some are (confusingly) marketed as "DataFlash" */
{ "at25fs010", INFO(0x1f6601, 0, 32 * 1024, 4, SECT_4K | SPI_NOR_HAS_LOCK)
.fixups = &atmel_at25fs_fixups },
{ "at25fs040", INFO(0x1f6604, 0, 64 * 1024, 8, SECT_4K | SPI_NOR_HAS_LOCK)
.fixups = &atmel_at25fs_fixups },
{ "at25df041a", INFO(0x1f4401, 0, 64 * 1024, 8,
SECT_4K | SPI_NOR_HAS_LOCK | SPI_NOR_SWP_IS_VOLATILE)
.fixups = &atmel_global_protection_fixups },
{ "at25df321", INFO(0x1f4700, 0, 64 * 1024, 64,
SECT_4K | SPI_NOR_HAS_LOCK | SPI_NOR_SWP_IS_VOLATILE)
.fixups = &atmel_global_protection_fixups },
{ "at25df321a", INFO(0x1f4701, 0, 64 * 1024, 64,
SECT_4K | SPI_NOR_HAS_LOCK | SPI_NOR_SWP_IS_VOLATILE)
.fixups = &atmel_global_protection_fixups },
{ "at25df641", INFO(0x1f4800, 0, 64 * 1024, 128,
SECT_4K | SPI_NOR_HAS_LOCK | SPI_NOR_SWP_IS_VOLATILE)
.fixups = &atmel_global_protection_fixups },
{ "at25sl321", INFO(0x1f4216, 0, 64 * 1024, 64,
SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ) },
{ "at26f004", INFO(0x1f0400, 0, 64 * 1024, 8, SECT_4K) },
{ "at26df081a", INFO(0x1f4501, 0, 64 * 1024, 16,
SECT_4K | SPI_NOR_HAS_LOCK | SPI_NOR_SWP_IS_VOLATILE)
.fixups = &atmel_global_protection_fixups },
{ "at26df161a", INFO(0x1f4601, 0, 64 * 1024, 32,
SECT_4K | SPI_NOR_HAS_LOCK | SPI_NOR_SWP_IS_VOLATILE)
.fixups = &atmel_global_protection_fixups },
{ "at26df321", INFO(0x1f4700, 0, 64 * 1024, 64,
SECT_4K | SPI_NOR_HAS_LOCK | SPI_NOR_SWP_IS_VOLATILE)
.fixups = &atmel_global_protection_fixups },
{ "at45db081d", INFO(0x1f2500, 0, 64 * 1024, 16, SECT_4K) },
};
const struct spi_nor_manufacturer spi_nor_atmel = {
.name = "atmel",
.parts = atmel_parts,
.nparts = ARRAY_SIZE(atmel_parts),
};