[PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks

[PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks

[Sai Prakash Ranjan]

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@codeaurora.org>
Co-developed-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
---
 drivers/iommu/arm/arm-smmu/arm-smmu.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

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;
 
@@ -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 = {
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation

Re: [PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks

[Robin Murphy]

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.

Robin.

> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> Co-developed-by: Rajendra Nayak <rnayak@codeaurora.org>
> Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
> ---
>   drivers/iommu/arm/arm-smmu/arm-smmu.c | 20 ++++++++++++++++++--
>   1 file changed, 18 insertions(+), 2 deletions(-)
> 
> 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;
>   
> @@ -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 = {
> 

Re: [PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks

[Robin Murphy]

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...

Robin.

>> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
>> Co-developed-by: Rajendra Nayak <rnayak@codeaurora.org>
>> Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
>> ---
>>   drivers/iommu/arm/arm-smmu/arm-smmu.c | 20 ++++++++++++++++++--
>>   1 file changed, 18 insertions(+), 2 deletions(-)
>>
>> 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;
>> @@ -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 = {
>>
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

Re: [PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks

[Sai Prakash Ranjan]

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

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a 
member
of Code Aurora Forum, hosted by The Linux Foundation

Re: [PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks

[Will Deacon]

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@codeaurora.org>
> Co-developed-by: Rajendra Nayak <rnayak@codeaurora.org>
> Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
> ---
>  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?

> 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?

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 = {
> -- 
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
> 

Re: [PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks

[Rob Clark]

On Mon, Aug 2, 2021 at 9:12 AM Will Deacon <will@kernel.org> 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@codeaurora.org>
> > Co-developed-by: Rajendra Nayak <rnayak@codeaurora.org>
> > Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
> > ---
> >  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?

AFAIU the device_link stuff should keep the SMMU clocked as long as
the GPU is alive, so I think this should work out ok.. ie. the SMMU
won't suspend while the GPU is not suspended.

BR,
-R


> > 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?
>
> 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 = {
> > --
> > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> > of Code Aurora Forum, hosted by The Linux Foundation
> >
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

Re: [PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks

[Sai Prakash Ranjan]

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@codeaurora.org>
>> Co-developed-by: Rajendra Nayak <rnayak@codeaurora.org>
>> Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
>> ---
>>  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 = {
>> --
>> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a 
>> member
>> of Code Aurora Forum, hosted by The Linux Foundation
>> 

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a 
member
of Code Aurora Forum, hosted by The Linux Foundation

Re: [PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks

[Sai Prakash Ranjan]

On 2021-08-03 11:36, Sai Prakash Ranjan wrote:
> 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@codeaurora.org>
>>> Co-developed-by: Rajendra Nayak <rnayak@codeaurora.org>
>>> Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
>>> ---
>>>  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.
> 

Nonetheless, it won't hurt to unprepare if clk enable fails as that is
the correct thing anyway, so I have added it and sent a v2.

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 = {
>>> --
>>> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a 
>>> member
>>> of Code Aurora Forum, hosted by The Linux Foundation
>>> 

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