Subject: Re: [RFC PATCH v2 09/11] devfreq: exynos-bus: Add interconnect functionality to exynos-bus

From: Chanwoo Choi <[email-masked]>
Date: Wed, 25 Sep 2019 16:03:17 +0900

Hi,

I need the time to dig the ICC framework
to understand them detailed. After that, I'll review this.

Basically, I agree this approach. But, I'm wondering
the existing binding method between 'bus_leftbus' and 'bus_dmc'.
From before, I thought that devfreq framework need to
enhance the binding method between parent devfreq device
and passive devfreq device instead of 'devfreq' property.

On this patch, use the same binding way between
'bus_leftbus' and 'bus_dmc' with 'parent' property
as following:

+++ b/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
@@ -106,6 +106,7 @@
 &bus_leftbus {
 	devfreq-events = <&ppmu_leftbus_3>, <&ppmu_rightbus_3>;
 	vdd-supply = <&buck3_reg>;
+	parent = <&bus_dmc>;
 	status = "okay";
 };

I'm not sure about continuing to use this method for new feature.
If possible, hope to replace the existing binding style
with new method like of_graph. Actually, I don't know the correct method.

On 19. 9. 19. 오후 11:22, Artur Świgoń wrote:
> From: Artur Świgoń <[email-masked]>
> 
> This patch adds interconnect functionality to the exynos-bus devfreq
> driver.
> 
> The SoC topology is a graph (or, more specifically, a tree) and most of
> its edges are taken from the devfreq parent-child hierarchy (cf.
> Documentation/devicetree/bindings/devfreq/exynos-bus.txt). Due to
> unspecified relative probing order, -EPROBE_DEFER may be propagated to
> guarantee that a child is probed before its parent.
> 
> Each bus is now an interconnect provider and an interconnect node as well
> (cf. Documentation/interconnect/interconnect.rst), i.e. every bus registers
> itself as a node. Node IDs are not hardcoded but rather assigned at
> runtime, in probing order (subject to the above-mentioned exception
> regarding relative order). This approach allows for using this driver with
> various Exynos SoCs.
> 
> Frequencies requested via the interconnect API for a given node are
> propagated to devfreq using dev_pm_qos_update_request(). Please note that
> it is not an error when CONFIG_INTERCONNECT is 'n', in which case all
> interconnect API functions are no-op.
> 
> Signed-off-by: Artur Świgoń <[email-masked]>
> ---
>  drivers/devfreq/exynos-bus.c | 153 +++++++++++++++++++++++++++++++++++
>  1 file changed, 153 insertions(+)
> 
> diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
> index 8d44810cac69..e0232202720d 100644
> --- a/drivers/devfreq/exynos-bus.c
> +++ b/drivers/devfreq/exynos-bus.c
> @@ -14,14 +14,19 @@
>  #include <linux/devfreq-event.h>
>  #include <linux/device.h>
>  #include <linux/export.h>
> +#include <linux/idr.h>
> +#include <linux/interconnect-provider.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/pm_opp.h>
> +#include <linux/pm_qos.h>
>  #include <linux/platform_device.h>
>  #include <linux/regulator/consumer.h>
>  
>  #define DEFAULT_SATURATION_RATIO	40
>  
> +#define icc_units_to_khz(x) ((x) / 8)
> +
>  struct exynos_bus {
>  	struct device *dev;
>  
> @@ -35,6 +40,12 @@ struct exynos_bus {
>  	struct opp_table *opp_table;
>  	struct clk *clk;
>  	unsigned int ratio;
> +
> +	/* One provider per bus, one node per provider */
> +	struct icc_provider provider;
> +	struct icc_node *node;
> +
> +	struct dev_pm_qos_request qos_req;
>  };
>  
>  /*
> @@ -59,6 +70,13 @@ exynos_bus_ops_edev(enable_edev);
>  exynos_bus_ops_edev(disable_edev);
>  exynos_bus_ops_edev(set_event);
>  
> +static int exynos_bus_next_id(void)
> +{
> +	static DEFINE_IDA(exynos_bus_icc_ida);
> +
> +	return ida_alloc(&exynos_bus_icc_ida, GFP_KERNEL);
> +}
> +
>  static int exynos_bus_get_event(struct exynos_bus *bus,
>  				struct devfreq_event_data *edata)
>  {
> @@ -171,6 +189,38 @@ static void exynos_bus_passive_exit(struct device *dev)
>  	clk_disable_unprepare(bus->clk);
>  }
>  
> +static int exynos_bus_icc_set(struct icc_node *src, struct icc_node *dst)
> +{
> +	struct exynos_bus *src_bus = src->data, *dst_bus = dst->data;
> +	s32 src_freq = icc_units_to_khz(src->avg_bw);
> +	s32 dst_freq = icc_units_to_khz(dst->avg_bw);
> +
> +	dev_pm_qos_update_request(&src_bus->qos_req, src_freq);
> +	dev_pm_qos_update_request(&dst_bus->qos_req, dst_freq);
> +
> +	return 0;
> +}
> +
> +static int exynos_bus_icc_aggregate(struct icc_node *node, u32 tag, u32 avg_bw,
> +				    u32 peak_bw, u32 *agg_avg, u32 *agg_peak)
> +{
> +	*agg_avg += avg_bw;
> +	*agg_peak = max(*agg_peak, peak_bw);
> +
> +	return 0;
> +}
> +
> +static struct icc_node *exynos_bus_icc_xlate(struct of_phandle_args *spec,
> +					     void *data)
> +{
> +	struct exynos_bus *bus = data;
> +
> +	if (spec->np != bus->dev->of_node)
> +		return ERR_PTR(-EINVAL);
> +
> +	return bus->node;
> +}
> +
>  static int exynos_bus_parent_parse_of(struct device_node *np,
>  					struct exynos_bus *bus)
>  {
> @@ -366,6 +416,101 @@ static int exynos_bus_profile_init_passive(struct exynos_bus *bus,
>  	return 0;
>  }
>  
> +static int exynos_bus_icc_connect(struct exynos_bus *bus)
> +{
> +	struct device_node *np = bus->dev->of_node;
> +	struct devfreq *parent_devfreq;
> +	struct icc_node *parent_node = NULL;
> +	struct of_phandle_args args;
> +	int ret = 0;
> +
> +	parent_devfreq = devfreq_get_devfreq_by_phandle(bus->dev, 0);
> +	if (!IS_ERR(parent_devfreq)) {
> +		struct exynos_bus *parent_bus;
> +
> +		parent_bus = dev_get_drvdata(parent_devfreq->dev.parent);
> +		parent_node = parent_bus->node;
> +	} else {
> +		/* Look for parent in DT */
> +		int num = of_count_phandle_with_args(np, "parent",
> +						     "#interconnect-cells");
> +		if (num != 1)
> +			goto out; /* 'parent' is optional */
> +
> +		ret = of_parse_phandle_with_args(np, "parent",
> +						 "#interconnect-cells",
> +						 0, &args);
> +		if (ret < 0)
> +			goto out;
> +
> +		of_node_put(args.np);
> +
> +		parent_node = of_icc_get_from_provider(&args);
> +		if (IS_ERR(parent_node)) {
> +			/* May be -EPROBE_DEFER */
> +			ret = PTR_ERR(parent_node);
> +			goto out;
> +		}
> +	}

> +
> +	ret = icc_link_create(bus->node, parent_node->id);
> +
> +out:
> +	return ret;
> +}
> +
> +static int exynos_bus_icc_init(struct exynos_bus *bus)
> +{
> +	struct device *dev = bus->dev;
> +	struct icc_provider *provider = &bus->provider;
> +	struct icc_node *node;
> +	int id, ret;
> +
> +	/* Initialize the interconnect provider */
> +	provider->set = exynos_bus_icc_set;
> +	provider->aggregate = exynos_bus_icc_aggregate;
> +	provider->xlate = exynos_bus_icc_xlate;
> +	provider->dev = dev;
> +	provider->data = bus;
> +
> +	ret = icc_provider_add(provider);
> +	if (ret < 0)
> +		goto out;
> +
> +	ret = id = exynos_bus_next_id();
> +	if (ret < 0)
> +		goto err_node;
> +
> +	node = icc_node_create(id);
> +	if (IS_ERR(node)) {
> +		ret = PTR_ERR(node);
> +		goto err_node;
> +	}
> +
> +	bus->node = node;
> +	node->name = dev->of_node->name;
> +	node->data = bus;
> +	icc_node_add(node, provider);
> +
> +	ret = exynos_bus_icc_connect(bus);
> +	if (ret < 0)
> +		goto err_connect;
> +
> +	ret = dev_pm_qos_add_request(bus->devfreq->dev.parent, &bus->qos_req,
> +				     DEV_PM_QOS_MIN_FREQUENCY, 0);
> +
> +out:
> +	return ret;
> +
> +err_connect:
> +	icc_node_del(node);
> +	icc_node_destroy(id);
> +err_node:
> +	icc_provider_del(provider);
> +
> +	return ret;
> +}
> +
>  static int exynos_bus_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -415,6 +560,14 @@ static int exynos_bus_probe(struct platform_device *pdev)
>  	if (ret < 0)
>  		goto err;
>  
> +	/*
> +	 * Initialize interconnect provider. A return value of -ENOTSUPP means
> +	 * that CONFIG_INTERCONNECT is disabled.
> +	 */
> +	ret = exynos_bus_icc_init(bus);
> +	if (ret < 0 && ret != -ENOTSUPP)
> +		goto err;
> +
>  	max_state = bus->devfreq->profile->max_state;
>  	min_freq = (bus->devfreq->profile->freq_table[0] / 1000);
>  	max_freq = (bus->devfreq->profile->freq_table[max_state - 1] / 1000);
> 

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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