Re: [PATCH v3 3/7] clk: qcom: gdsc: enable optional power domain support

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Fri 09 Jul 12:31 CDT 2021, Dmitry Baryshkov wrote:

> On sm8250 dispcc and videocc registers are powered up by the MMCX power
> domain. Currently we use a regulator to enable this domain on demand,
> however this has some consequences, as genpd code is not reentrant.
> 
> Teach Qualcomm clock controller code about setting up runtime PM and
> using specified for gdsc powerup.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>  drivers/clk/qcom/common.c | 37 +++++++++++++++++++++++++++++++------
>  drivers/clk/qcom/gdsc.c   |  4 ++++
>  2 files changed, 35 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/clk/qcom/common.c b/drivers/clk/qcom/common.c
> index 60d2a78d1395..43d8f8feeb3c 100644
> --- a/drivers/clk/qcom/common.c
> +++ b/drivers/clk/qcom/common.c
> @@ -10,6 +10,7 @@
>  #include <linux/clk-provider.h>
>  #include <linux/reset-controller.h>
>  #include <linux/of.h>
> +#include <linux/pm_runtime.h>
>  
>  #include "common.h"
>  #include "clk-rcg.h"
> @@ -224,6 +225,11 @@ static struct clk_hw *qcom_cc_clk_hw_get(struct of_phandle_args *clkspec,
>  	return cc->rclks[idx] ? &cc->rclks[idx]->hw : NULL;
>  }
>  
> +static void qcom_cc_pm_runtime_disable(void *data)
> +{
> +	pm_runtime_disable(data);
> +}
> +
>  int qcom_cc_really_probe(struct platform_device *pdev,
>  			 const struct qcom_cc_desc *desc, struct regmap *regmap)
>  {
> @@ -241,6 +247,18 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>  	if (!cc)
>  		return -ENOMEM;
>  
> +	pm_runtime_enable(dev);

In turingcc-qcs404.c I'm using pm_runtime to have the clock framework
ensure that the iface clock is enabled during clock operations, so this
will result in a "unbalanced enable" warning.

> +	ret = pm_runtime_get_sync(dev);

I don't think you should wrap the entire initialization in a
pm_runtime_get_sync()/put() region. Instead follow the clock framework
and wrap gdsc initialization that needs to touch the hardware in:

	if (pm_runtime_enabled())
		pm_runtime_get_sync();

I do however think that as of this patch, when probe returns MMCX might
very well be turned off, as the only user (this driver) has pm_runtime
enabled and it's idle. So I think you should introduce the
pm_runtime_get()/put() in the gdsc functions before this patch.


To summarize, I think you should rely on the individual clock drivers to
pm_runtime_enable()/disable().

> +	if (ret < 0) {
> +		pm_runtime_put(dev);
> +		pm_runtime_disable(dev);
> +		return ret;
> +	}
> +
> +	ret = devm_add_action_or_reset(dev, qcom_cc_pm_runtime_disable, dev);
> +	if (ret)
> +		goto err;
> +
>  	reset = &cc->reset;
>  	reset->rcdev.of_node = dev->of_node;
>  	reset->rcdev.ops = &qcom_reset_ops;
> @@ -251,7 +269,7 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>  
>  	ret = devm_reset_controller_register(dev, &reset->rcdev);
>  	if (ret)
> -		return ret;
> +		goto err;
>  
>  	if (desc->gdscs && desc->num_gdscs) {
>  		scd = devm_kzalloc(dev, sizeof(*scd), GFP_KERNEL);
> @@ -262,11 +280,11 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>  		scd->num = desc->num_gdscs;
>  		ret = gdsc_register(scd, &reset->rcdev, regmap);
>  		if (ret)
> -			return ret;
> +			goto err;
>  		ret = devm_add_action_or_reset(dev, qcom_cc_gdsc_unregister,
>  					       scd);
>  		if (ret)
> -			return ret;
> +			goto err;
>  	}
>  
>  	cc->rclks = rclks;
> @@ -277,7 +295,7 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>  	for (i = 0; i < num_clk_hws; i++) {
>  		ret = devm_clk_hw_register(dev, clk_hws[i]);
>  		if (ret)
> -			return ret;
> +			goto err;
>  	}
>  
>  	for (i = 0; i < num_clks; i++) {
> @@ -286,14 +304,21 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>  
>  		ret = devm_clk_register_regmap(dev, rclks[i]);
>  		if (ret)
> -			return ret;
> +			goto err;
>  	}
>  
>  	ret = devm_of_clk_add_hw_provider(dev, qcom_cc_clk_hw_get, cc);
>  	if (ret)
> -		return ret;
> +		goto err;
> +
> +	pm_runtime_put(dev);
>  
>  	return 0;
> +
> +err:
> +	pm_runtime_put(dev);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(qcom_cc_really_probe);
>  
> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> index 51ed640e527b..ccd36617d067 100644
> --- a/drivers/clk/qcom/gdsc.c
> +++ b/drivers/clk/qcom/gdsc.c
> @@ -439,6 +439,8 @@ int gdsc_register(struct gdsc_desc *desc,
>  			continue;
>  		if (scs[i]->parent)
>  			pm_genpd_add_subdomain(scs[i]->parent, &scs[i]->pd);
> +		else if (!IS_ERR_OR_NULL(dev->pm_domain))
> +			pm_genpd_add_subdomain(pd_to_genpd(dev->pm_domain), &scs[i]->pd);

Nice, I didn't know that we could fish it out of the dev.

Regards,
Bjorn

>  	}
>  
>  	return of_genpd_add_provider_onecell(dev->of_node, data);
> @@ -457,6 +459,8 @@ void gdsc_unregister(struct gdsc_desc *desc)
>  			continue;
>  		if (scs[i]->parent)
>  			pm_genpd_remove_subdomain(scs[i]->parent, &scs[i]->pd);
> +		else if (!IS_ERR_OR_NULL(dev->pm_domain))
> +			pm_genpd_remove_subdomain(pd_to_genpd(dev->pm_domain), &scs[i]->pd);
>  	}
>  	of_genpd_del_provider(dev->of_node);
>  }
> -- 
> 2.30.2
>