[U-Boot] spi and block bits

[Jagan Teki]

On 17 April 2015 at 12:45, Michael Walle <michael at walle.cc> wrote:
> Am 2015-04-16 20:32, schrieb Jagan Teki:
>>
>> On 9 February 2015 at 04:57, Michael Walle <michael at walle.cc> wrote:
>>>
>>> Hi there,
>>>
>>> I stumbled across a situation where the SPI flash on my board was write
>>> protected and i could not unlock it in the bootloader. This is especially
>>> unfortunate because the recovery mechanism relies on the bootloader to be
>>> able to erase the environment.
>>
>>
>> Which flash vendor it is? seems like there is a hardware write protected
>> mechanism in ST MICRON flashes.
>
>
> it is a st micron. (see include/configs/lsxl.h)
>
>> Please refer that, may be this looks similar to that W#/Vpp
>> CONFIG_SYS_SPI_ST_ENABLE_WP_PIN
>
>
> But it isn't related to that.
>
> My point was, if linux enables the lock bits, there is no way you can write
> to the flash in the bootloader anymore. Because it is not possible to clear
> these bits in u-boot. If you have a macronix or an ST flash the block
> protection bits are cleared on probe. see sf_probe.c:
>
>
>         /* Flash powers up read-only, so clear BP# bits */
> #if defined(CONFIG_SPI_FLASH_ATMEL) || \
>         defined(CONFIG_SPI_FLASH_MACRONIX) || \
>         defined(CONFIG_SPI_FLASH_SST)
>                 spi_flash_cmd_write_status(flash, 0);
> #endif

So are you saying clearing BP# bits should also required for Micron as
you need to access it on bootloader?


>
> Although as the comment says, it is because these chips power up in
> read-only state by default. In my case, linux would set these bits.
>
> To be more precise, the fw_setenv will leave the flash write protected and i
> cannot modify the environment in the bootloader anymore.

I couldn't understand your point can you elaborate, if clearing BP# required for
Micron how could it accessed in Linux?

thanks!
-- 
Jagan.