Re: [PATCH 0/3] iommu/arm-smmu: Qualcomm bootsplash/efifb

On Mon 24 May 07:03 CDT 2021, Lee Jones wrote:

On Wed, 8 Jan 2020 at 09:16, Will Deacon [off-list ref] wrote:

quoted

On Thu, Dec 26, 2019 at 02:17:06PM -0800, Bjorn Andersson wrote:

quoted

These patches implements the stream mapping inheritance that's necessary

in

quoted

order to not hit a security violation as the display hardware looses its

stream

quoted

mapping during initialization of arm-smmu in various Qualcomm platforms.

This was previously posted as an RFC [1], changes since then involves the
rebase and migration of the read-back code to the Qualcomm specific
implementation, the mapping is maintained indefinitely - to handle probe
deferring clients - and rewritten commit messages.

I don't think we should solve this in a Qualcomm-specific manner. Please
can
you take a look at the proposal from Thierry [1] and see whether or not it
works for you?

Did this or Thierry's solution ever gain traction?

There was a few pieces that landed in the common code which allowed us
to deal with the quirks of the Qualcomm platform (turned out that just
reading back the settings wasn't the only piece necessary).

The "generic" solution is essentially the second half of
qcom_smmu_cfg_probe(), which ensures that as the SMMU is reset it will
do so with bypass mappings for all stream mappings the boot loader left
us.

Or are all the parties still 'solving' this downstream?

I believe that Qualcomm has adopted the upstream solution in their
downstream kernel.

Regards,
Bjorn

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