Hey Joerg,
Thanks for taking time to review
the series!
On 2020-03-10 16:53, Joerg Roedel wrote:
On Mon, Mar 09, 2020 at 11:52:52PM +0530, Sibi Sankar wrote:
The Q6 modem sub-system has direct access to DDR through memnoc and
an indirect access routed through a SMMU which MSS CE (crypto engine
sub-component of MSS) uses during out of reset sequence. Request
direct
mapping for the modem-firmware subdevice since smmu is not expected
to provide access control/translation for these SIDs (sandboxing of
the
modem is achieved through XPUs engaged using SMC calls).
So the DMA accesses are initiated by the firmware and need to be direct
mapped? Which memory region do they access?
The accesses are initiated by the firmware
and they access modem reserved regions.
However as explained in ^^ any accesses
outside the region will result in a violation
and is controlled through XPUs (protection units).
With ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT y
the firmware SIDs will explicitly need to
be directly mapped to avoid observing
global faults in the absence of secure
firmware (TrustZone) programming the modem
SIDs as S2CR-Bypass.
Regards,
Joerg
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