Re: [PATCH] media: dt-bindings: qcom,sc7280-venus: Allow one IOMMU entry

[Vikash Garodia]

Hello,

On 1/30/2024 1:17 PM, Luca Weiss wrote:
> On Mon Jan 29, 2024 at 6:37 PM CET, Conor Dooley wrote:
>> On Mon, Jan 29, 2024 at 08:48:54AM +0100, Luca Weiss wrote:
>>> Some SC7280-based boards crash when providing the "secure_non_pixel"
>>> context bank, so allow only one iommu in the bindings also.
>>>
>>> Signed-off-by: Luca Weiss <luca.weiss@xxxxxxxxxxxxx>
>>
>> Do we have any idea why this happens? How is someone supposed to know
>> whether or not their system requires you to only provide one iommu?
>> Yes, a crash might be the obvious answer, but is there a way of knowing
>> without the crashes?
> 
> +CC Vikash Garodia
> 
> Unfortunately I don't really have much more information than this
> message here:
> https://lore.kernel.org/linux-arm-msm/ff021f49-f81b-0fd1-bd2c-895dbbb03d56@xxxxxxxxxxx/
> 
> And see also the following replies for a bit more context, like this
> one:
> https://lore.kernel.org/linux-arm-msm/a4e8b531-49f9-f4a1-51cb-e422c56281cc@xxxxxxxxxxx/
> 
> Maybe Vikash can add some more info regarding this.

0x2184 is a secure SID i.e any transactions with that ID would be access
controlled by trustzone (TZ). SC7280 (chromebook) was designed without TZ, while
some other DT deriving from SC7280 (like qcm6490) might have TZ. Hence it is
good to move the iommu entry from SC7280 to chrome-common.

Regards,
Vikash