Hi Robin,
On 2021-07-27 16:03, Robin Murphy wrote:
On 2021-07-27 11:25, Robin Murphy wrote:
On 2021-07-27 10:33, Sai Prakash Ranjan wrote:
Some clocks for SMMU can have parent as XO such as
gpu_cc_hub_cx_int_clk
of GPU SMMU in QTI SC7280 SoC and in order to enter deep sleep states
in
such cases, we would need to drop the XO clock vote in unprepare call
and
this unprepare callback for XO is in RPMh (Resource Power
Manager-Hardened)
clock driver which controls RPMh managed clock resources for new QTI
SoCs
and is a blocking call.
Given we cannot have a sleeping calls such as clk_bulk_prepare() and
clk_bulk_unprepare() in arm-smmu runtime pm callbacks since the iommu
operations like map and unmap can be in atomic context and are in
fast
path, add this prepare and unprepare call to drop the XO vote only
for
system pm callbacks since it is not a fast path and we expect the
system
to enter deep sleep states with system pm as opposed to runtime pm.
This is a similar sequence of clock requests (prepare,enable and
disable,unprepare) in arm-smmu probe and remove.
Nope. We call arm_smmu_rpm_get(), which may resume the device, from
atomic contexts. clk_prepare() may sleep. This doesn't work.
Urgh, or maybe I skimmed the commit message too lightly *and* managed
to totally misread the patch, sorry :(
I'll wake up some more and try again later...
No worries, we took our time looking through that many times before
posting this :)
Thanks,
Sai
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