Message-ID: <CAGTfZH1wVKBQAantrpqPP7+penwxeJud=gjH=5vVmKbzTGE=cQ@mail.gmail.com>
Date:   Wed, 18 Dec 2019 19:39:44 +0900
From:   Chanwoo Choi <chanwoo@...nel.org>
To:     Artur Świgoń <a.swigon@...sung.com>
Cc:     Chanwoo Choi <cw00.choi@...sung.com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>, inki.dae@...sung.com,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        georgi.djakov@...aro.org,
        Leonard Crestez <leonard.crestez@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>
Subject: Re: [RFC PATCH v2 09/11] devfreq: exynos-bus: Add interconnect
 functionality to exynos-bus

Hi,

2019년 12월 18일 (수) 오후 7:19, Artur Świgoń <a.swigon@...sung.com>님이 작성:
>
> 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@...tner.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@...tner.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;

If you return right after, better to use dev_err.
If you use dev_warn, just show the warning message without return.

> }
>
> > > +   dev_pm_qos_update_request(&dst_bus->qos_req, dst_freq);
> >
> > ditto.
>
> OK (same as above).

ditto.

>
> > > +
> > > +   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.

OK.

>
> > 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
>
>


-- 
Best Regards,
Chanwoo Choi

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