Messages in this thread | | | Subject | Re: [PATCH v3] mtd: spi-nor: keep lock bits if they are non-volatile | From | Vignesh Raghavendra <> | Date | Wed, 30 Sep 2020 16:05:09 +0530 |
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On 3/27/20 9:29 PM, Michael Walle wrote: > Traditionally, linux unlocks the whole flash because there are legacy > devices which has the write protections 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. > [...] > Further, the commit 3e0930f109e76 ("mtd: spi-nor: Rework the disabling of > block write protection") expanded the unlock_all() feature to ANY flash > which supports locking. >
Appreciate the detail commit log.
> Signed-off-by: Michael Walle <michael@walle.cc> > --- > changes since v2: > - add Kconfig option to be able to retain legacy behaviour > - rebased the patch due to the spi-nor rewrite > - dropped the Fixes: tag, it doens't make sense after the spi-nor rewrite > - mention commit 3e0930f109e76 which further modified the unlock > behaviour. > > changes since v1: > - completely rewrote patch, the first version used a device tree flag > > drivers/mtd/spi-nor/Kconfig | 35 +++++++++++++++++++++++++++++ > drivers/mtd/spi-nor/atmel.c | 24 +++++++++++++------- > drivers/mtd/spi-nor/core.c | 44 ++++++++++++++++++++++++++++--------- > drivers/mtd/spi-nor/core.h | 6 +++++ > drivers/mtd/spi-nor/esmt.c | 6 ++--- > drivers/mtd/spi-nor/intel.c | 6 ++--- > drivers/mtd/spi-nor/sst.c | 21 +++++++++--------- > include/linux/mtd/spi-nor.h | 6 +++++ > 8 files changed, 114 insertions(+), 34 deletions(-) > > diff --git a/drivers/mtd/spi-nor/Kconfig b/drivers/mtd/spi-nor/Kconfig > index 6e816eafb312..647de17c81e2 100644 > --- a/drivers/mtd/spi-nor/Kconfig > +++ b/drivers/mtd/spi-nor/Kconfig > @@ -24,6 +24,41 @@ config MTD_SPI_NOR_USE_4K_SECTORS > Please note that some tools/drivers/filesystems may not work with > 4096 B erase size (e.g. UBIFS requires 15 KiB as a minimum). > > +choice > + prompt "Write protection at boot" > + default MTD_SPI_NOR_WP_DISABLE
These choice control how BP0-X bits are manipulated on boot. Hence, to be consistent should use Block Protection (BP) terminology throughout.
This would also be inline with most flash datasheets which also use term BP
> + > +config MTD_SPI_NOR_WP_DISABLE > + bool "Disable WP on any flashes (legacy behaviour)" > + help > + This option disables the write protection on any SPI flashes at > + boot-up. > + > + Don't use this if you intent to use the write protection of your > + SPI flash. This is only to keep backwards compatibility. > + > +config MTD_SPI_NOR_WP_DISABLE_ON_VOLATILE > + bool "Disable WP on flashes w/ volatile protection bits" > + help > + Some SPI flashes have volatile block protection bits, ie. after a > + power-up or a reset the flash is write protected by default. > + > + This option disables the write protection for these kind of flashes > + while keeping it enabled for any other SPI flashes which have > + non-volatile block protection bits. > + > + If you are unsure, select this option. > + > +config MTD_SPI_NOR_WP_KEEP > + bool "Keep write protection as is" > + help > + If you select this option the write protection of any SPI flashes > + will not be changed. If your flash is write protected or will be > + automatically write protected after power-up you have to manually > + unlock it before you are able to write to it. > + > +endchoice > + > source "drivers/mtd/spi-nor/controllers/Kconfig" > > endif # MTD_SPI_NOR
[...]
> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h > index 6f2f6b27173f..9a33c023717f 100644 > --- a/drivers/mtd/spi-nor/core.h > +++ b/drivers/mtd/spi-nor/core.h > @@ -26,6 +26,7 @@ enum spi_nor_option_flags { > SNOR_F_HAS_SR_TB_BIT6 = BIT(11), > SNOR_F_HAS_4BIT_BP = BIT(12), > SNOR_F_HAS_SR_BP3_BIT6 = BIT(13), > + SNOR_F_NEED_UNPROTECT = BIT(14), > }; > > struct spi_nor_read_command { > @@ -311,6 +312,11 @@ struct flash_info { > * BP3 is bit 6 of status register. > * Must be used with SPI_NOR_4BIT_BP. > */ > +#define SPI_NOR_UNPROTECT BIT(19) /* > + * Flash is write-protected after > + * power-up and needs a global > + * unprotect. > + */ >
It would be better to name the flag to indicate BP bits are volatile or powers up locked instead of SPI_NOR_UNPROTECT. This makes it easier to understand what this flag means wrt flash HW feature. Maybe:
SPI_NOR_LOCKED_ON_POWER_UP or SPI_NOR_BP_IS_VOLATILE
Reset looks fine to me
[...]
Regards Vignesh
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