Re: [GIT PULL] ARM: mvebu: dt64 for v7.2 (#1)

[Aleksander Jan Bajkowski <olek2@wp.pl>]

Hi Arnd,

On 09/06/2026 18:11, Arnd Bergmann wrote:
> On Fri, Jun 5, 2026, at 17:20, Gregory CLEMENT wrote:
>> ----------------------------------------------------------------
>> mvebu dt64 for 7.2 (part 1)
>>
>> Mark EIP97 as dma-coherent for Armada 3720
>>
>> ----------------------------------------------------------------
>> Aleksander Jan Bajkowski (1):
>>        arm64: dts: marvell: armada-37xx: mark EIP97 as dma-coherent
> Hi Gregory and Aleksander,
>
> I'm a bit surprised by this oneline change. Since you successfully tested
> this, I assume the change is correct, but I have two questions that
> I would like to have an answer for before I pull it.
By the way, the upstream safexcel driver works correctly only on coherent
platforms. On non-coherent platforms (MediaTek), the SHA-384 and SHA-512
selftests fail. Since the selftests pass on Armada's SoC, I assume I'm 
right.
I have a plan to send a patch upstream, which has long been maintained
downstream in OpenWRT[1]. But I need to think a bit more about how to do
this properly.
[1] 
https://github.com/openwrt/openwrt/blob/main/target/linux/mediatek/patches-6.18/401-crypto-fix-eip97-cache-incoherent.patch 

>
> - I would expect a missing 'dma-coherent' property to cause data
>    corruption, as the DMA master may write directly into the L2
>    cache, which is then invalidated before the CPU accesses it.
>    Do you have any idea how this one ends up working even when
>    the property is missing?
No idea. Don't have access the Armada SoC TRM. Maybe the folks at
Marvel will be able to explain it.
>
> - I see that the Product Brief for Armada 37xx mentions that it
>    has a "High-bandwidth, low-latency IO Cache Coherency" interconnect,
>    which also indicates that the patch is correct. However I don't
>    see why it's only the crypto engine that needs it. What about
>    the other high-speed DMA masters (neta, xhci, pcie, sata, ...)?
I didn't test to determine whether the other DMA masters are coherent.
But I'm assuming you're correct and they are also coherent. My recent
work has been focused on improving the Rambus/Verimatrix/Safenet crypto
drivers :)

Best regards,
Aleksander