Re: [PATCH 1/2] arm: mach-k3: am625: copy bootindex to OCRAM for main domain SPL

Vignesh Raghavendra
2024-03-05T04:36:57Z

On 05/03/24 01:57, Bryan Brattlof wrote:
> Hey Vignesh!
>
> On March 4, 2024 thus sayeth Vignesh Raghavendra:
>> Hi Wadim,
>>
>> On 26/02/24 19:00, Wadim Egorov wrote:
>>> Texas Instruments has begun enabling security settings on the SoCs it
>>> produces to instruct ROM and TIFS to begin protecting the Security
>>> Management Subsystem (SMS) from other binaries we load into the chip by
>>> default.
>>>
>>> One way ROM and TIFS do this is by enabling firewalls to protect the
>>> OCSRAM and HSM RAM regions they're using during bootup.
>>>
>>> The HSM RAM the wakeup SPL is in is firewalled by TIFS to protect
>>> itself from the main domain applications. This means the 'bootindex'
>>> value in HSM RAM, left by ROM to indicate if we're using the primary
>>> or secondary boot-method, must be moved to OCSRAM (that TIFS has open
>>> for us) before we make the jump to the main domain so the main domain's
>>> bootloaders can keep access to this information.
>>>
>>> Based on commit
>>> b672e8581070 ("arm: mach-k3: copy bootindex to OCRAM for main domain SPL")
>>>
>>
>> FYI, this is mostly a problem in non SPL flow (TI prosperity SBL for
>> example) where HSM RAM would be used by HSM firmware. This should be a
>> issue in R5 SPL flow. Do you see any issues today? If so, whats the
>> TIFS firmware being used?
>>
>>> Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
>>> ---
>>> arch/arm/mach-k3/Kconfig | 3 ++-
>>> arch/arm/mach-k3/am625_init.c | 15 +++++++++++++--
>>> arch/arm/mach-k3/include/mach/am62_hardware.h | 15 +++++++++++++++
>>> 3 files changed, 30 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/arm/mach-k3/Kconfig b/arch/arm/mach-k3/Kconfig
>>> index 03898424c9..f5d06593f7 100644
>>> --- a/arch/arm/mach-k3/Kconfig
>>> +++ b/arch/arm/mach-k3/Kconfig
>>> @@ -75,7 +75,8 @@ config SYS_K3_BOOT_PARAM_TABLE_INDEX
>>> default 0x41cffbfc if SOC_K3_J721E
>>> default 0x41cfdbfc if SOC_K3_J721S2
>>> default 0x701bebfc if SOC_K3_AM642
>>> - default 0x43c3f290 if SOC_K3_AM625
>>> + default 0x43c3f290 if SOC_K3_AM625 && CPU_V7R
>>> + default 0x7000f290 if SOC_K3_AM625 && ARM64
>>> default 0x43c3f290 if SOC_K3_AM62A7 && CPU_V7R
>>> default 0x7000f290 if SOC_K3_AM62A7 && ARM64
>>> help
>>> diff --git a/arch/arm/mach-k3/am625_init.c b/arch/arm/mach-k3/am625_init.c
>>> index 6c96e88114..67cf63b103 100644
>>> --- a/arch/arm/mach-k3/am625_init.c
>>> +++ b/arch/arm/mach-k3/am625_init.c
>>> @@ -35,8 +35,10 @@ static struct rom_extended_boot_data bootdata __section(".data");
>>> static void store_boot_info_from_rom(void)
>>> {
>>> bootindex = *(u32 *)(CONFIG_SYS_K3_BOOT_PARAM_TABLE_INDEX);
>>> - memcpy(&bootdata, (uintptr_t *)ROM_EXTENDED_BOOT_DATA_INFO,
>>> - sizeof(struct rom_extended_boot_data));
>>> + if (IS_ENABLED(CONFIG_CPU_V7R)) {
>>> + memcpy(&bootdata, (uintptr_t *)ROM_EXTENDED_BOOT_DATA_INFO,
>>> + sizeof(struct rom_extended_boot_data));
>>> + }
>>> }
>>>
>>> static void ctrl_mmr_unlock(void)
>>> @@ -175,6 +177,15 @@ void board_init_f(ulong dummy)
>>> k3_sysfw_loader(true, NULL, NULL);
>>> }
>>>
>>> +#if defined(CONFIG_CPU_V7R)
>>> + /*
>>> + * Relocate boot information to OCRAM (after TIFS has opend this
>>> + * region for us) so the next bootloader stages can keep access to
>>> + * primary vs backup bootmodes.
>>> + */
>>> + writel(bootindex, K3_BOOT_PARAM_TABLE_INDEX_OCRAM);
>>> +#endif
>>> +
>>> /*
>>> * Force probe of clk_k3 driver here to ensure basic default clock
>>> * configuration is always done.
>>> diff --git a/arch/arm/mach-k3/include/mach/am62_hardware.h b/arch/arm/mach-k3/include/mach/am62_hardware.h
>>> index 54380f36e1..9f504f4642 100644
>>> --- a/arch/arm/mach-k3/include/mach/am62_hardware.h
>>> +++ b/arch/arm/mach-k3/include/mach/am62_hardware.h
>>> @@ -76,8 +76,23 @@
>>> #define CTRLMMR_MCU_RST_CTRL (MCU_CTRL_MMR0_BASE + 0x18170)
>>>
>>> #define ROM_EXTENDED_BOOT_DATA_INFO 0x43c3f1e0
>>> +#define K3_BOOT_PARAM_TABLE_INDEX_OCRAM 0x7000F290
>>>
>>> +/*
>>> + * During the boot process ROM will kill anything that writes to OCSRAM.
>>
>> R5 ROM is long gone when R5 SPL starts, how would it kill anything?
>
> Looks like this was based on my patch long ago for the AM62Ax family.
> From what little I remember about this was ROM is leaving behind a
> firewall that we need TIFS's help to bring down for us. So I just
> blamed ROM ;)

Thats true. ROM does bare minimum and so wont open up firewall around
main SRAM. but TIFS does, so you should be able to access this region
post k3_sysfw_loader().

>
> IDK if this is an issue for the AM62x family though.
>

It might be if one tries to "select" DT using EEPROM detect before SYSFW
is up. But that's not the case any more right?

>>
>>> + * This means the wakeup SPL cannot use this region during boot. To
>>> + * complicate things, TIFS will set a firewall between HSM RAM and the
>>> + * main domain.
>>> + *
>>> + * So, during the wakeup SPL, we will need to store the EEPROM data
>>> + * somewhere in HSM RAM, and the main domain's SPL will need to store it
>>> + * somewhere in OCSRAM
>>> + */
>>> +#ifdef CONFIG_CPU_V7R
>>> #define TI_SRAM_SCRATCH_BOARD_EEPROM_START 0x43c30000
>>> +#else
>>> + #define TI_SRAM_SCRATCH_BOARD_EEPROM_START 0x70000001
>>
>> Why not 0x70000000 ?
>
> Ah an off by one by me :) 0x70000000 should be fine
>
>>
>>> +#endif /* CONFIG_CPU_V7R */
>>>
>>
>> Can't we store directly in OCRAM in both stages? This RAM should be
>> accessible post TIFS is up (ie post k3_sysfw_loader() call)
>
> I'll have to double check but I think this should work.
>
> ~Bryan

--
Regards
Vignesh