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

Beleswar Prasad Padhi b-padhi at ti.com
Tue Dec 9 06:53:20 CET 2025 

On 08/12/25 19:51, Andrew Davis wrote:
> On 12/8/25 3:25 AM, Beleswar Prasad Padhi wrote:
>>
>> 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).
>
> Seem PRAM ("Protected" RAM) isn't all it claims to be, better route then
> is to convert our existing uses of PRAM to SYS_MEM_TOP_HIDE, which seems
> more modern and uses KConfig.


Posted patch for the same:
https://lore.kernel.org/all/20251209055043.1410085-1-b-padhi@ti.com/

Thanks,
Beleswar

>
> Andrew
>
>>
>> [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
>>>>>>>
>>>>>
>>>
>

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