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SubjectRe: [RFC PATCH v2 09/11] devfreq: exynos-bus: Add interconnect functionality to exynos-bus
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Hi,

Thank you for the review.

On Mon, 2019-12-16 at 09:44 +0900, Chanwoo Choi wrote:
> Hi,
>
> On 9/19/19 11:22 PM, Artur Świgoń wrote:
> > From: Artur Świgoń <a.swigon@partner.samsung.com>
> >
> > 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 <a.swigon@partner.samsung.com>
> > ---
> > 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)
>
> icc_units_to_khz() -> kpbs_to_khz()

OK

> > +
> > 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);
>
> Have to check the return value.
> If return error, show the waring with dev_warn.

OK, I will change it to:

ret = dev_pm_qos_update_request(&src_bus->qos_req, src_freq);
if (ret < 0) {
dev_warn(src_bus->dev, "failed to update PM QoS request");
return ret;
}

> > + dev_pm_qos_update_request(&dst_bus->qos_req, dst_freq);
>
> ditto.

OK (same as above).

> > +
> > + 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);
>
>
> Actually, I agree your approach. I think that it is very useful
> and necessary to guarantee the PM QoS requirements between devices.
>
> But,
> As I already commented, I'm not sure that the "parent" property
> is proper for only this driver. If possible, you better to get
> the parent phandle through other way like OF graph.
>
> If you suggest the standard way to make the tree between
> the exynos-bus, I'll agree.

As I commented in the answer to patch 08, I will use the
'exynos,interconnect-parent-node' property for bus_display,
bus_leftbus and bus_dmc.

> Also, for interconnect path, you have to add the connection
> between 'bus_display' and 'bus_leftbus' regardless
> of the existing 'devfreq' property.
> - bus_display - bus_leftbus - bus_dmc
>
> > + 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;
>
> Return error without goto because there is no any requirement
> to free the resource before.

OK.

> > +
> > + 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,
>
> Check whether this line is over 80 char.

It looks like 77 columns to me.

> > + DEV_PM_QOS_MIN_FREQUENCY, 0);
>
> Check the return value.

OK.

>
> > +
> > +out:
>
> Remove this goto due to not necessary.
>
> > + return ret;
>
> return 0;

OK.

Please also note that this function as well as exynos_bus_icc_connect()
will
slightly change in v3 due to the changes regarding DT properties.

>
> > +
> > +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;
>
> Print error message.
> dev_err(dev, "failed to initialize the interconnect provider");

OK.

>
> > +
> > 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,
--
Artur Świgoń
Samsung R&D Institute Poland
Samsung Electronics


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