On 2021-08-02 21:42, Will Deacon wrote:
On Tue, Jul 27, 2021 at 03:03:22PM +0530, 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.
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
Co-developed-by: Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>
Signed-off-by: Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>
---
drivers/iommu/arm/arm-smmu/arm-smmu.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
[+Rob]
How does this work with that funny GPU which writes to the SMMU
registers
directly? Does the SMMU need to remain independently clocked for that
to
work or is it all in the same clock domain?
As Rob mentioned, device link should take care of all the dependencies
between
SMMU and its consumers. But not sure how the question relates to this
patch as this
change is for system pm and not runtime pm, so it is exactly the
sequence of
SMMU probe/remove which if works currently for that GPU SMMU, then it
should work
just fine for system suspend and resume as well.
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c
b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index d3c6f54110a5..9561ba4c5d39 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -2277,6 +2277,13 @@ static int __maybe_unused
arm_smmu_runtime_suspend(struct device *dev)
static int __maybe_unused arm_smmu_pm_resume(struct device *dev)
{
+ int ret;
+ struct arm_smmu_device *smmu = dev_get_drvdata(dev);
+
+ ret = clk_bulk_prepare(smmu->num_clks, smmu->clks);
+ if (ret)
+ return ret;
+
if (pm_runtime_suspended(dev))
return 0;
If we subsequently fail to enable the clks in arm_smmu_runtime_resume()
should we unprepare them again?
If we are unable to turn on the clks then its fatal and we will not live
for long.
Thanks,
Sai
Will
@@ -2285,10 +2292,19 @@ static int __maybe_unused
arm_smmu_pm_resume(struct device *dev)
static int __maybe_unused arm_smmu_pm_suspend(struct device *dev)
{
+ int ret = 0;
+ struct arm_smmu_device *smmu = dev_get_drvdata(dev);
+
if (pm_runtime_suspended(dev))
- return 0;
+ goto clk_unprepare;
- return arm_smmu_runtime_suspend(dev);
+ ret = arm_smmu_runtime_suspend(dev);
+ if (ret)
+ return ret;
+
+clk_unprepare:
+ clk_bulk_unprepare(smmu->num_clks, smmu->clks);
+ return ret;
}
static const struct dev_pm_ops arm_smmu_pm_ops = {
--
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--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member
of Code Aurora Forum, hosted by The Linux Foundation
