From: andrew-sh.cheng <andrew-sh.cheng@mediatek.com>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
devicetree@vger.kernel.org, srv_heupstream@mediatek.com,
linux-pm@vger.kernel.org, Viresh Kumar <viresh.kumar@linaro.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
linux-kernel@vger.kernel.org,
Chanwoo Choi <cw00.choi@samsung.com>,
Kyungmin Park <kyungmin.park@samsung.com>,
Rob Herring <robh+dt@kernel.org>,
linux-mediatek@lists.infradead.org,
MyungJoo Ham <myungjoo.ham@samsung.com>,
Matthias Brugger <matthias.bgg@gmail.com>,
fan.chen@mediatek.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 3/3] devfreq: add mediatek cci devfreq
Date: Sat, 16 Feb 2019 11:07:45 +0800 [thread overview]
Message-ID: <1550286465.23797.20.camel@mtksdaap41> (raw)
In-Reply-To: <20190201201338.GS81583@google.com>
On Fri, 2019-02-01 at 12:13 -0800, Matthias Kaehlcke wrote:
> Hi Andrew,
>
> On Tue, Jan 29, 2019 at 02:35:04PM +0800, Andrew-sh Cheng wrote:
> > From: "Andrew-sh.Cheng" <andrew-sh.cheng@mediatek.com>
>
> the 'From' tag is only needed when you send patches not authored by
> yourself. It doesn't do any harm either, but you can drop it in future
> submissions.
Got it~
>
> > For big/little cpu cluster architecture,
> > not only CPU frequency, but CCI frequency will also affect performance.
>
> This doesn't provide much information, I suggest to drop it unless
> others find it valuable.
I will remove it in next patch.
>
> > Little cores and cci share the same buck in Mediatek mt8183 IC,
> > so we add a CCI devfreq which will get notification when buck voltage
> > is changed, then CCI devfreq can set cci frequency as high as
> > possible.
>
> Possible alternative:
>
> "This adds a devfreq driver for the Cache Coherent Interconnect (CCI)
> of the Mediatek MT8183.
>
> On the MT8183 the CCI is supplied by the same regulator as the LITTLE
> cores. The driver is notified when the regulator voltage changes
> (driven by cpufreq) and adjusts the CCI frequency to the maximum
> possible value."
>
> Feel free to ignore or to adjust.
Thank you. This description provide suitable information.
>
> > Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>
> > ---
> > drivers/devfreq/Kconfig | 9 ++
> > drivers/devfreq/Makefile | 1 +
> > drivers/devfreq/mt8183-cci-devfreq.c | 224 +++++++++++++++++++++++++++++++++++
> > 3 files changed, 234 insertions(+)
> > create mode 100644 drivers/devfreq/mt8183-cci-devfreq.c
> >
> > diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> > index 6a172d3..0b14aab 100644
> > --- a/drivers/devfreq/Kconfig
> > +++ b/drivers/devfreq/Kconfig
> > @@ -113,6 +113,15 @@ config ARM_RK3399_DMC_DEVFREQ
> > It sets the frequency for the memory controller and reads the usage counts
> > from hardware.
> >
> > +config ARM_MT8183_CCI_DEVFREQ
> > + tristate "MT8183 CCI DEVFREQ Driver"
> > + depends on ARM_MEDIATEK_CPUFREQ
> > + help
> > + This adds devfreq for cci clock
>
> "This adds a devfreq driver for the Cache Coherent Interconnect (CCI)
> of the Mediatek MT8183"?
Yes, I describe more detail in next patch.
>
> > + which is shared the same regulator with cpu cluster.
> > + It can track buck voltage and update a proper cci frequency.
> > + Use notification to get regulator status.
>
> not sure how important this info is here, sounds more like an
> implementation detail to me.
Yes, just describe the situation.
>
> > +
> > source "drivers/devfreq/event/Kconfig"
> >
> > endif # PM_DEVFREQ
> > diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
> > index 32b8d4d..25afe8c 100644
> > --- a/drivers/devfreq/Makefile
> > +++ b/drivers/devfreq/Makefile
> > @@ -11,6 +11,7 @@ obj-$(CONFIG_DEVFREQ_GOV_PASSIVE) += governor_passive.o
> > obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ) += exynos-bus.o
> > obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ) += rk3399_dmc.o
> > obj-$(CONFIG_ARM_TEGRA_DEVFREQ) += tegra-devfreq.o
> > +obj-$(CONFIG_ARM_MT8183_CCI_DEVFREQ) += mt8183-cci-devfreq.o
> >
> > # DEVFREQ Event Drivers
> > obj-$(CONFIG_PM_DEVFREQ_EVENT) += event/
> > diff --git a/drivers/devfreq/mt8183-cci-devfreq.c b/drivers/devfreq/mt8183-cci-devfreq.c
> > new file mode 100644
> > index 0000000..4837892
> > --- /dev/null
> > +++ b/drivers/devfreq/mt8183-cci-devfreq.c
> > @@ -0,0 +1,224 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +//
> > +// Copyright (c) 2018 MediaTek Inc.
>
> 2019 :)
Got it :)
>
> > +#include <linux/cpu.h>
> > +#include <linux/cpufreq.h>
> > +#include <linux/devfreq.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/regulator/consumer.h>
> > +
> > +#include "governor.h"
> > +
> > +struct cci_devfreq_data {
>
> nit: consider dropping the '_data' suffix, it doesn't add much/any
> value.
I will change to struct cci_devfreq in next patch.
>
> > + struct devfreq *devfreq;
> > + struct regulator *proc_reg;
> > + struct clk *cci_clk;
> > + unsigned long buck_volt;
>
> proc_reg_uV?
>
> place after proc_reg
OK~
>
> > + int volt_increasing;
>
> should be bool
>
> actually, is it really needed? See comment in cci_devfreq_regulator_notifier()
>
You are right. I will remove this and use notification data to judge the
condition in next patch.
> > + struct notifier_block nb;
> > +};
> > +
> > +static int mtk_cci_governor_get_target(struct devfreq *devfreq,
> > + unsigned long *freq)
> > +{
> > + struct cci_devfreq_data *cci_devdata;
>
> nit: consider calling it 'cci_df' (here and elsewhere). In the context
> the abbreviation is clear and there is less clutter when accessing
> fields in the structure.
OK, I will change it in next patch.
>
> > + int i, opp_count;
> > + struct dev_pm_opp *opp;
> > + unsigned long opp_rate, opp_voltage;
> > +
> > + cci_devdata = dev_get_drvdata(devfreq->dev.parent);
> > +
> > + /* find available frequency */
> > + opp_count = dev_pm_opp_get_opp_count(devfreq->dev.parent);
> > + for (i = 0, opp_rate = ULONG_MAX; i < opp_count; i++, opp_rate--) {
> > + opp = dev_pm_opp_find_freq_floor(devfreq->dev.parent,
> > + &opp_rate);
> > + opp_voltage = dev_pm_opp_get_voltage(opp);
> > + dev_pm_opp_put(opp);
> > +
> > + if (opp_voltage <= cci_devdata->buck_volt)
> > + break;
> > + }
> > + *freq = opp_rate;
> > +
> > + return 0;
> > +}
> > +
> > +static int mtk_cci_governor_event_handler(struct devfreq *devfreq,
> > + unsigned int event, void *data)
> > +{
> > + return 0;
> > +}
> > +
> > +static struct devfreq_governor mtk_cci_devfreq_governor = {
> > + .name = "voltage_monitor",
>
> "mtk_cci_vmon" or similar?
OK. I will change it in next patch.
> > + .get_target_freq = mtk_cci_governor_get_target,
> > + .event_handler = mtk_cci_governor_event_handler,
> > +};
> > +
> > +static int mtk_cci_devfreq_target(struct device *dev, unsigned long *freq,
> > + u32 flags)
> > +{
> > + struct cci_devfreq_data *cci_devdata;
> > +
> > + cci_devdata = dev_get_drvdata(dev);
> > +
> > + clk_set_rate(cci_devdata->cci_clk, *freq);
> > +
> > + return 0;
> > +}
> > +
> > +static struct devfreq_dev_profile cci_devfreq_profile = {
> > + .polling_ms = 0,
> > + .target = mtk_cci_devfreq_target,
> > +};
> > +
> > +static int cci_devfreq_regulator_notifier(struct notifier_block *nb,
> > + unsigned long val, void *data)
> > +{
> > + struct cci_devfreq_data *cci_devdata =
> > + container_of(nb, struct cci_devfreq_data, nb);
> > +
> > + /* deal with reduce frequency */
> > + if (val & REGULATOR_EVENT_PRE_VOLTAGE_CHANGE) {
> > + struct pre_voltage_change_data *pvc_data = data;
> > +
> > + if (pvc_data->old_uV > pvc_data->min_uV) {
>
> I would suggest to invert the condition. For humans it is easier to
> parse "is the new voltage smaller than the previous one", than
> viceversa.
Got it.
>
> > + cci_devdata->volt_increasing = 0;
> > + cci_devdata->buck_volt =
> > + (unsigned long)(pvc_data->min_uV);
> > + mutex_lock(&cci_devdata->devfreq->lock);
> > + update_devfreq(cci_devdata->devfreq);
> > + mutex_unlock(&cci_devdata->devfreq->lock);
> > + } else {
> > + cci_devdata->volt_increasing = 1;
> > + }
> > + }
>
> nit: add empty line
I will modify in next patch.
>
> > + /* deal with abort reduce frequency */
>
> Shouldn't this be "abort voltage change?". If so I suggest to drop the
> comment, REGULATOR_EVENT_ABORT_VOLTAGE_CHANGE in the condition makes
> it clear.
OK
>
> > + if ((val & REGULATOR_EVENT_ABORT_VOLTAGE_CHANGE) ||
> > + /* deal with increase frequency */
> > + ((val & REGULATOR_EVENT_VOLTAGE_CHANGE) &&
> > + cci_devdata->volt_increasing == 1)) {
>
> to check for a voltage increase you could use 'cci_devdata->buck_volt
> < (unsigned long)data' instead of ->volt_increasing.
Thank you for suggestion.
I will modify in next patch.
>
> > + cci_devdata->buck_volt = (unsigned long)data;
> > + mutex_lock(&cci_devdata->devfreq->lock);
> > + update_devfreq(cci_devdata->devfreq);
> > + mutex_unlock(&cci_devdata->devfreq->lock);
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int mtk_cci_devfreq_probe(struct platform_device *pdev)
> > +{
> > + struct device *cci_dev = &pdev->dev;
> > + struct cci_devfreq_data *cci_devdata;
> > + struct notifier_block *nb;
> > + int ret;
> > +
> > + dev_pm_opp_of_add_table(&pdev->dev);
> > +
> > + cci_devdata = devm_kzalloc(cci_dev, sizeof(*cci_devdata), GFP_KERNEL);
> > + if (!cci_devdata)
> > + return -ENOMEM;
> > + nb = &cci_devdata->nb;
> > + cci_devdata->cci_clk = ERR_PTR(-ENODEV);
>
> initialization not needed, the field is assigned a few lines below.
>
> > + cci_devdata->proc_reg = ERR_PTR(-ENODEV);
>
> also not really needed with the right gotos in place
OK. I will remove unnecessary initialization.
>
> > +
> > + cci_devdata->cci_clk = clk_get(cci_dev, "cci_clock");
> > + ret = PTR_ERR_OR_ZERO(cci_devdata->cci_clk);
> > + if (ret) {
> > + if (ret == -EPROBE_DEFER)
> > + pr_err("cci clock not ready, retry\n");
> > + else
> > + pr_err("no clock for cci: %d\n", ret);
> > +
> > + goto out_free_resources;
>
> nothing to be freed here, just return ret.
OK.
>
> > + }
> > +
> > + cci_devdata->proc_reg = regulator_get_optional(cci_dev, "proc");
> > + ret = PTR_ERR_OR_ZERO(cci_devdata->proc_reg);
> > + if (ret) {
> > + if (ret == -EPROBE_DEFER)
> > + pr_err("cci regulator not ready, retry\n");
> > + else
> > + pr_err("no regulator for cci: %d\n", ret);
> > +
> > + goto out_free_resources;
> > + }
> > +
> > + platform_set_drvdata(pdev, cci_devdata);
> > +
> > + /* create cci_devfreq and add to cci device.
> > + * governor is voltage_monitor.
> > + * governor will get platform_device data to make decision.
> > + */
> > + cci_devdata->devfreq = devm_devfreq_add_device(cci_dev,
> > + &cci_devfreq_profile,
> > + "voltage_monitor",
>
> adjust name in case you follow my suggestion above.
>
> check cci_devdata->devfreq for errors.
Will add error check in next patch.
>
> > + NULL);
> > +
> > + nb->notifier_call = cci_devfreq_regulator_notifier;
> > + regulator_register_notifier(cci_devdata->proc_reg,
> > + nb);
> > +
> > + return 0;
> > +
> > +out_free_resources:
> > + if (!IS_ERR(cci_devdata->cci_clk))
> > + clk_put(cci_devdata->cci_clk);
> > + if (!IS_ERR(cci_devdata->proc_reg))
> > + regulator_put(cci_devdata->proc_reg);
>
> use individual labels and get rid of the IS_ERRs.
>
> e.g.
>
> err_put_reg:
> regulator_put(cci_devdata->proc_reg);
>
> err_put_clk:
> clk_put(cci_devdata->cci_clk);
>
>
> and jump to the corresponding lable above.
Got it. I will use individual label and remove the IS_ERR checking.
>
> > +
> > + return ret;
> > +}
> > +
> > +static const struct of_device_id mediatek_cci_devfreq_of_match[] = {
> > + { .compatible = "mediatek,mt8183-cci" },
> > + { },
> > +};
> > +MODULE_DEVICE_TABLE(of, mediatek_cci_devfreq_of_match);
> > +
> > +static struct platform_driver cci_devfreq_driver = {
> > + .probe = mtk_cci_devfreq_probe,
> > + .driver = {
> > + .name = "mediatek-cci-devfreq",
> > + .of_match_table = mediatek_cci_devfreq_of_match,
> > + },
> > +};
> > +
> > +static int __init mtk_cci_devfreq_init(void)
> > +{
> > + int ret = 0;
>
> initialization not needed
OK.
>
> > +
> > + ret = devfreq_add_governor(&mtk_cci_devfreq_governor);
> > + if (ret) {
> > + pr_err("%s: failed to add governor: %d\n", __func__, ret);
> > + return ret;
> > + }
> > +
> > + ret = platform_driver_register(&cci_devfreq_driver);
> > + if (ret)
> > + devfreq_remove_governor(&mtk_cci_devfreq_governor);
> > +
> > + return ret;
> > +}
> > +module_init(mtk_cci_devfreq_init)
> > +
> > +static void __exit mtk_cci_devfreq_exit(void)
> > +{
> > + int ret = 0;
>
> initialization not needed
OK.
>
> > + platform_driver_unregister(&cci_devfreq_driver);
> > +
> > + ret = devfreq_remove_governor(&mtk_cci_devfreq_governor);
> > + if (ret)
> > + pr_err("%s: failed to remove governor: %d\n", __func__, ret);
>
> typically you reverse the order of initialization, i.e. remove the
> governor, then unregister the driver.
OK. I will change it in next patch.
>
> > +}
> > +module_exit(mtk_cci_devfreq_exit)
> > +
> > +MODULE_LICENSE("GPL v2");
> > +MODULE_DESCRIPTION("Mediatek CCI devfreq driver");
> > +MODULE_AUTHOR("andrew-sh.cheng");
>
> should be either "Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>" or
> "Andrew-sh.Cheng"
I will change to "Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>" :)
>
> Cheers
>
> Matthias
>
> _______________________________________________
> Linux-mediatek mailing list
> Linux-mediatek@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-mediatek
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next prev parent reply other threads:[~2019-02-16 3:08 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-29 6:35 [PATCH 0/3] Add cpufreq and cci devfreq for mt8183 Andrew-sh Cheng
2019-01-29 6:35 ` [PATCH 1/3] cpufreq: mediatek: add mt8183 cpufreq support Andrew-sh Cheng
2019-01-29 10:13 ` Viresh Kumar
2019-02-11 13:19 ` andrew-sh.cheng
2019-01-29 6:35 ` [PATCH 2/3] dt-bindings: devfreq: add compatible for mt8183 cci devfreq Andrew-sh Cheng
2019-02-12 1:00 ` Chanwoo Choi
2019-02-16 0:09 ` andrew-sh.cheng
2019-01-29 6:35 ` [PATCH 3/3] devfreq: add mediatek " Andrew-sh Cheng
2019-02-01 3:43 ` Nicolas Boichat
2019-02-12 9:05 ` andrew-sh.cheng
2019-02-01 20:13 ` Matthias Kaehlcke
2019-02-16 3:07 ` andrew-sh.cheng [this message]
2019-02-12 4:06 ` Chanwoo Choi
2019-02-16 6:16 ` andrew-sh.cheng
[not found] ` <CGME20190129063600epcas2p255b062c64f22555692ff895634ea4eb0@epcms1p4>
2019-01-29 8:17 ` MyungJoo Ham
2019-02-11 13:21 ` andrew-sh.cheng
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