Hello Marco, On 3/10/25 12:36, Marco Felsch wrote: > Current tests showed that fusing just the single field-return bit(0) on > i.MX8MP SoCs brick the device. So such a device is bricked permanently with no way to upload a bootloader again to fuse the remainder of the bits? Interesting thing to not document :/ Cheers, Ahmad > > All i.MX8M SoCs have a single field-return bit except for the i.MX8MP > which requires a pattern. The pattern is not documented but was > discussed here [1] and the final u-boot commit [2] added the support > accordingly. > > This commit is based on the outcome of [1, 2]. > > [1] https://lore.kernel.org/all/20240621130626.729666-1-paul.geurts@xxxxxxxxxxxxxxxxxxxxxxxxx/ > [2] https://github.com/u-boot/u-boot/blob/v2025.01/arch/arm/mach-imx/hab.c#L35 > > Tested-by: Johannes Schneider <johannes.schneider@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Marco Felsch <m.felsch@xxxxxxxxxxxxxx> > --- > drivers/hab/hab.c | 12 +++++++++++- > include/mach/imx/ocotp-fusemap.h | 1 + > 2 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/hab/hab.c b/drivers/hab/hab.c > index 73d470be131e..74ba4a48557c 100644 > --- a/drivers/hab/hab.c > +++ b/drivers/hab/hab.c > @@ -252,6 +252,12 @@ static int imx8m_hab_revoke_key_ocotp(unsigned key_idx) > return ret; > } > > +/* > + * The fuse pattern for i.MX8M Plus is 0x28001401, but bit 2 is already set from factory. > + * This means when field return is set, the fuse word value reads 0x28001405 > + */ > +#define MX8MP_FIELD_RETURN_PATTERN 0x28001401 > + > static int imx8m_hab_field_return_ocotp(void) > { > int ret; > @@ -264,7 +270,11 @@ static int imx8m_hab_field_return_ocotp(void) > if (ret == 1) > return -EINVAL; > > - ret = imx_ocotp_write_field(MX8M_OCOTP_FIELD_RETURN, 1); > + if (cpu_is_mx8mp()) > + ret = imx_ocotp_write_field(MX8MP_OCOTP_FIELD_RETURN, > + MX8MP_FIELD_RETURN_PATTERN); > + else > + ret = imx_ocotp_write_field(MX8M_OCOTP_FIELD_RETURN, 1); > > return ret; > } > diff --git a/include/mach/imx/ocotp-fusemap.h b/include/mach/imx/ocotp-fusemap.h > index 37f1ee8298c2..587fe8b15eab 100644 > --- a/include/mach/imx/ocotp-fusemap.h > +++ b/include/mach/imx/ocotp-fusemap.h > @@ -68,6 +68,7 @@ > #define MX8MP_OCOTP_ROM_NO_LOG (OCOTP_WORD(0x480) | OCOTP_BIT(22) | OCOTP_WIDTH(1)) > #define MX8M_OCOTP_RECOVERY_SDMMC_BOOT_DIS (OCOTP_WORD(0x490) | OCOTP_BIT(23) | OCOTP_WIDTH(1)) > #define MX8M_OCOTP_FIELD_RETURN (OCOTP_WORD(0x630) | OCOTP_BIT(0) | OCOTP_WIDTH(1)) > +#define MX8MP_OCOTP_FIELD_RETURN (OCOTP_WORD(0x630) | OCOTP_BIT(0) | OCOTP_WIDTH(32)) > #define MX8M_OCOTP_SRK_REVOKE (OCOTP_WORD(0x670) | OCOTP_BIT(0) | OCOTP_WIDTH(4)) > > #endif /* __MACH_IMX_OCOTP_FUSEMAP_H */
