[PATCH v2] configs: am571x_hs_evm_defconfig: Reserve EMIF memory used by PPA

Mon Dec 8 10:25:42 CET 2025

On 05/12/25 20:12, Andrew Davis wrote:
>
>
> On 12/5/25 1:32 AM, Beleswar Prasad Padhi wrote:
>>
>> On 02/12/25 18:47, Andrew Davis wrote:
>>> On 12/1/25 11:56 PM, Beleswar Prasad Padhi wrote:
>>>>
>>>> On 02/12/25 00:58, Andrew Davis wrote:
>>>>> On 11/28/25 9:04 AM, Beleswar Padhi wrote:
>>>>>> The AM571x SoC has 1 GB DDR space. As part of normal re-location process
>>>>>> U-Boot copies itself to the top of DDR bank. However, on HS devices, the
>>>>>> top 37 MB is used by PPA and is firewalled. This results in an exception
>>>>>> and the boot fails.
>>>>>>
>>>>>> Introduce a new defconfig for AM571x HS platforms and set
>>>>>> CONFIG_SYS_MEM_TOP_HIDE to reserve the top 38 MB memory (aligned to 2MB
>>>>>> as per page size for ARM32) for the same.
>>>>>>
>>>>>
>>>>> This "SYS_MEM_TOP_HIDE" looks new, for other OMAP-class HS devices we
>>>>> use "CFG_PRAM"[0], seems these two configs do the same thing, could probably
>>>>> combine them in some way..
>>>>>
>>>>> As CFG_PRAM is set based on TI_SECURE_EMIF_TOTAL_REGION_SIZE which is 32MB
>>>>
>>>>
>>>> CFG_PRAM is only set if TI_SECURE_EMIF_REGION_START is not set, but we
>>>> have it set it to 0xbdb00000 in the am57xx_hs_evm_defconfig.
>>>>
>>>> https://github.com/u-boot/u-boot/blob/master/include/configs/ti_omap5_common.h#L75-L81
>>>>
>>>>> for all other AM57x, why is this needed only for AM571?
>>>>
>>>>
>>>> Other AM57x boards have >1 GiB DDR. So, the top of DDR space does not
>>>> intersect with the firewalled EMIF region (0xbdb00000). Only in case of
>>>> AM571x, the top of DDR collides with firewalled region, so boot fails while
>>>> doing reloc.
>>>>
>>>
>>> Is there some way to detect this at runtime? Nothing prevents any of the
>>> AM57x SoCs being used on boards with 1GB DDR (although they also might use
>>> a different defconfig). How do we deal with this for K3 devices? Some use
>>> an OP-TEE address aligned at 512MB and I'm sure one of them have that amount
>>> of DDR.
>>
>>
>> Well, actually not...
>> It's the AM62 SIP platform. From DT, it would look like OPTEE is at the top of the
>> DDR[1], but we do a FDT fixup here in u-boot to replace the OPTEE to the start
>> of DDR[2]
>>
>> [1]: https://github.com/torvalds/linux/blob/master/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi#L71
>> [2]: https://github.com/u-boot/u-boot/blob/master/arch/arm/mach-k3/am62x/am625_fdt.c#L84
>>
>> I am not sure if we can do such a thing here for mem used by PPA/firmware
>> as it could assume it has that memory hardcoded.
>>
>>>
>>>>> We build for all
>>>>> the AM57x with one defconfig, so this new defconfig will go unused. Just set
>>>>> the default CFG_PRAM size to 64MB (same as AM43x),
>>>>
>>>>
>>>> I am guessing all AM43x devices have the same amount of memory unlike
>>>> AM57x devices? If we set CFG_PRAM to 38MB by default, won't we lose out
>>>> that memory on other devices which do not face this limitation?
>>>>
>>>
>>> We only really supported "officially" the AM437x-EVM. But our over-focus
>>> on just our EVMs caused us to make assumptions that would later make
>>> it difficult to add support for customer boards. Assuming DDR size was
>>> one such assumption, and should a customer board have the "wrong" DDR
>>> size things like this would break.
>>>
>>> So instead of making another one-off fix to get one of our EVMs working,
>>> I'm trying to think of a way we can make this work automatically for any
>>> combination of DDR size and firewalled region.
>>
>> TL;DR
>> I think adding that dynamic support would be tied up only for TI usecase?
>>
>> Hmm yes, I get your point. But to be able to do this dynamically, we
>> would want to see if gd->relocaddr intersects with CFG_PRAM:
>>
>> Case 1:
>> gd->relocaddr > (SECURE_REGION_START + SECURE_REGION_SIZE)
>> = Best case. U-Boot relocates to an address higher than firewalled addr
>>
>> Case 2:
>> gd->relocaddr <= (SECURE_REGION_START + SECURE_REGION_SIZE)
>> = Fixup needed. U-Boot relocates to an address which could overlap
>> with secure region. Update the gd->relocaddr to a lower address range
>> which won't overlap with secure region:
>>
>>      reloc_text_size = (RAM_TOP - gd->relocaddr);
>>      gd->relocaddr = SECURE_REGION_START - reloc_text_size;
>>
>>
>> And ofcourse, we can't put this logic in the existing 'reserve_pram'[3]
>> INITCALL because gd->relocaddr gets modified in the subsequent
>> initcalls like 'reserve_trace'. We would want to introduce a new
>> INITCALL which would be invoked after all reserve_* initcalls and
>> before the reloc_* initcalls; where we can put this logic.
>>
>> Let me know if you think this is worth adding, or is an overkill and
>> we can live happily with CFG_PRAM = 38 MB for all AM57x devices :)
>
> Thanks for doing all this evaluation. I don't think this will be
> the last time we run into this issue, but for now let's just make
> CFG_PRAM = 64 MB for all AM57x devices and create the perfect solution
> later.

Thanks, I tried setting CFG_PRAM but it still ended up in a firewall
exception. I guess this is because CFG_PRAM only ensures U-Boot doesn't
relocate to that protected address[4], however that memory is still open
for access by anything else if needed. Whereas, SYS_MEM_TOP_HIDE reduces
the ram size itself[5], which ensures that memory is not visible to
U-Boot at all (either for reloc, or general usage).

[4]: https://github.com/u-boot/u-boot/blob/master/common/board_f.c#L391
[5]: https://github.com/u-boot/u-boot/blob/master/common/board_f.c#L371

Thanks,
Beleswar

>
> Andrew
>
>>
>> [3]: https://github.com/u-boot/u-boot/blob/master/common/board_f.c#L990
>>
>> Thanks,
>> Beleswar
>>
>>>
>>> Andrew
>>>
>>>> Thanks,
>>>> Beleswar
>>>>
>>>>> should be enough for all
>>>>> and doesn't hurt to have more than needed reserved to be safe.
>>>>>
>>>>> Andrew
>>>>>
>>>>> [0] https://github.com/u-boot/u-boot/blob/master/include/configs/am43xx_evm.h#L153
>>>>>
>>>>>> Signed-off-by: Beleswar Padhi <b-padhi at ti.com>
>>>>>> ---
>>>>>> Fix boot for TI AM571x HS EVM board
>>>>>> v2: Changelog:
>>>>>> 1. Drop [PATCH v1 2/2] in v2 series. There is no need to add reserved
>>>>>> memory node in DT as it is done by U-Boot as part of FDT fixups
>>>>>> https://github.com/u-boot/u-boot/blob/master/arch/arm/mach-omap2/fdt-common.c#L72-L107
>>>>>> 2. Add entry in MAINTAINERS for new config.
>>>>>> 3. Update commit message to use memory size in MB than raw hex bytes
>>>>>>
>>>>>> Link to v1:
>>>>>> https://lore.kernel.org/all/20251128064353.1295063-1-b-padhi@ti.com/
>>>>>>
>>>>>> Test logs:
>>>>>> https://gist.github.com/3V3RYONE/e86b3f4551986b0400d0e0f66d6ecc66
>>>>>>
>>>>>>     MAINTAINERS                     | 1 +
>>>>>>     configs/am571x_hs_evm_defconfig | 3 +++
>>>>>>     2 files changed, 4 insertions(+)
>>>>>>     create mode 100644 configs/am571x_hs_evm_defconfig
>>>>>>
>>>>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>>>>> index b43dae882b3..e5d564cd760 100644
>>>>>> --- a/MAINTAINERS
>>>>>> +++ b/MAINTAINERS
>>>>>> @@ -1780,6 +1780,7 @@ F:    configs/am335x_hs_evm_spi_defconfig
>>>>>>     F:    configs/am335x_hs_evm_uart_defconfig
>>>>>>     F:    configs/am43xx_hs_evm_defconfig
>>>>>>     F:    configs/am43xx_hs_evm_qspi_defconfig
>>>>>> +F:    configs/am571x_hs_evm_defconfig
>>>>>>     F:    configs/am57xx_hs_evm_defconfig
>>>>>>     F:    configs/am57xx_hs_evm_usb_defconfig
>>>>>>     F:    configs/dra7xx_hs_evm_defconfig
>>>>>> diff --git a/configs/am571x_hs_evm_defconfig b/configs/am571x_hs_evm_defconfig
>>>>>> new file mode 100644
>>>>>> index 00000000000..7e44ee5221a
>>>>>> --- /dev/null
>>>>>> +++ b/configs/am571x_hs_evm_defconfig
>>>>>> @@ -0,0 +1,3 @@
>>>>>> +#include <configs/am57xx_hs_evm_defconfig>
>>>>>> +
>>>>>> +CONFIG_SYS_MEM_TOP_HIDE=0x2600000
>>>>>
>>>
>