Re: [PATCH 3/6] clk: qcom: gdsc: enable optional power domain support

[Bjorn Andersson]

On Wed 30 Jun 08:31 CDT 2021, Dmitry Baryshkov wrote:

> On sm8250 dispcc and videocc registers are powered up by the MMCX power
> domain. Currently we used 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 power domains and
> using them for gdsc control.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>

There's a proposal to add a generic binding for statically assigning a
performance states here:

https://lore.kernel.org/linux-arm-msm/1622095949-2014-1-git-send-email-rnayak@xxxxxxxxxxxxxx/


But that said, do you really need this?

The requirement for driving MMCX to LOW_SVS on SM8250 (and NOM on
SM8150/SC8180x) seems to only come from the fact that you push MDP_CLK
to 460MHz in &mdss.

But then in &mdss_mdp you do the same using an opp-table based on the
actual MDP_CLK, which per its power-domains will scale MMCX accordingly.


So wouldn't it be sufficient to ensure that MDSS_GDSC is parented by
MMCX and then use opp-tables associated with the devices that scales the
clock and thereby actually carries the "required-opps".


I presume your testing indicates that it doesn't matter on sm8250, but
as stated above, 460MHz on sm8150/sc8180x requires nominal, so per your
suggestion we'd have to vote nominal in &mdss, which means that if the
DPU decides to go to 200MHz the &mdss will still keep the voltage at
NOM, even though the DPU's opp-table says that LOW_SVS is sufficient.

Regards,
Bjorn

> ---
>  drivers/clk/qcom/common.c | 55 ++++++++++++++++++++++++++++++++++-----
>  drivers/clk/qcom/gdsc.c   |  6 +++++
>  2 files changed, 55 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/clk/qcom/common.c b/drivers/clk/qcom/common.c
> index 60d2a78d1395..eeb5b8c93032 100644
> --- a/drivers/clk/qcom/common.c
> +++ b/drivers/clk/qcom/common.c
> @@ -10,6 +10,8 @@
>  #include <linux/clk-provider.h>
>  #include <linux/reset-controller.h>
>  #include <linux/of.h>
> +#include <linux/pm_opp.h>
> +#include <linux/pm_runtime.h>
>  
>  #include "common.h"
>  #include "clk-rcg.h"
> @@ -76,6 +78,16 @@ qcom_cc_map(struct platform_device *pdev, const struct qcom_cc_desc *desc)
>  	struct resource *res;
>  	struct device *dev = &pdev->dev;
>  
> +	if (of_find_property(dev->of_node, "required-opps", NULL)) {
> +		int pd_opp;
> +
> +		pd_opp = of_get_required_opp_performance_state(dev->of_node, 0);
> +		if (pd_opp < 0)
> +			return ERR_PTR(pd_opp);
> +
> +		dev_pm_genpd_set_performance_state(dev, pd_opp);
> +	}
> +
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	base = devm_ioremap_resource(dev, res);
>  	if (IS_ERR(base))
> @@ -224,6 +236,11 @@ 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)
>  {
> @@ -236,11 +253,28 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>  	struct clk_regmap **rclks = desc->clks;
>  	size_t num_clk_hws = desc->num_clk_hws;
>  	struct clk_hw **clk_hws = desc->clk_hws;
> +	bool use_pm = false;
>  
>  	cc = devm_kzalloc(dev, sizeof(*cc), GFP_KERNEL);
>  	if (!cc)
>  		return -ENOMEM;
>  
> +	if (of_find_property(dev->of_node, "required-opps", NULL)) {
> +		use_pm = true;
> +
> +		pm_runtime_enable(dev);
> +		ret = pm_runtime_get_sync(dev);
> +		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)
> +			return ret;
> +	}
> +
>  	reset = &cc->reset;
>  	reset->rcdev.of_node = dev->of_node;
>  	reset->rcdev.ops = &qcom_reset_ops;
> @@ -251,7 +285,7 @@ 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 +296,11 @@ 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 +311,7 @@ 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 +320,23 @@ 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;
> +
> +	if (use_pm)
> +		pm_runtime_put(dev);
>  
>  	return 0;
> +
> +err:
> +	if (use_pm)
> +		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..40c384bda4fc 100644
> --- a/drivers/clk/qcom/gdsc.c
> +++ b/drivers/clk/qcom/gdsc.c
> @@ -11,6 +11,7 @@
>  #include <linux/kernel.h>
>  #include <linux/ktime.h>
>  #include <linux/pm_domain.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/regmap.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/reset-controller.h>
> @@ -237,6 +238,8 @@ static int gdsc_enable(struct generic_pm_domain *domain)
>  	struct gdsc *sc = domain_to_gdsc(domain);
>  	int ret;
>  
> +	pm_runtime_get_sync(domain->dev.parent);
> +
>  	if (sc->pwrsts == PWRSTS_ON)
>  		return gdsc_deassert_reset(sc);
>  
> @@ -326,6 +329,8 @@ static int gdsc_disable(struct generic_pm_domain *domain)
>  	if (sc->flags & CLAMP_IO)
>  		gdsc_assert_clamp_io(sc);
>  
> +	pm_runtime_put(domain->dev.parent);
> +
>  	return 0;
>  }
>  
> @@ -427,6 +432,7 @@ int gdsc_register(struct gdsc_desc *desc,
>  			continue;
>  		scs[i]->regmap = regmap;
>  		scs[i]->rcdev = rcdev;
> +		scs[i]->pd.dev.parent = desc->dev;
>  		ret = gdsc_init(scs[i]);
>  		if (ret)
>  			return ret;
> -- 
> 2.30.2
>