Re: [PATCH v6 2/2] PM / devfreq: mediatek: Introduce MediaTek CCI devfreq driver

From: Chanwoo Choi
Date: Tue Jun 07 2022 - 00:52:23 EST


On 5/30/22 9:16 PM, AngeloGioacchino Del Regno wrote:
> Il 27/05/22 13:00, Johnson Wang ha scritto:
>> We introduce a devfreq driver for the MediaTek Cache Coherent Interconnect
>> (CCI) used by some MediaTek SoCs.
>>
>> In this driver, we use the passive devfreq driver to get target frequencies
>> and adjust voltages accordingly. In MT8183 and MT8186, the MediaTek CCI
>> is supplied by the same regulators with the little core CPUs.
>>
>> Signed-off-by: Jia-Wei Chang <jia-wei.chang@xxxxxxxxxxxx>
>> Signed-off-by: Johnson Wang <johnson.wang@xxxxxxxxxxxx>
>> Acked-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
>> ---
>> This patch depends on "devfreq-testing"[1].
>> [1]https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git/log/?h=devfreq-testing
>> ---
>>   drivers/devfreq/Kconfig           |  10 +
>>   drivers/devfreq/Makefile          |   1 +
>>   drivers/devfreq/mtk-cci-devfreq.c | 441 ++++++++++++++++++++++++++++++
>>   3 files changed, 452 insertions(+)
>>   create mode 100644 drivers/devfreq/mtk-cci-devfreq.c
>>
>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>> index 87eb2b837e68..9754d8b31621 100644
>> --- a/drivers/devfreq/Kconfig
>> +++ b/drivers/devfreq/Kconfig
>> @@ -120,6 +120,16 @@ config ARM_TEGRA_DEVFREQ
>>         It reads ACTMON counters of memory controllers and adjusts the
>>         operating frequencies and voltages with OPP support.
>>   +config ARM_MEDIATEK_CCI_DEVFREQ
>> +    tristate "MEDIATEK CCI DEVFREQ Driver"
>> +    depends on ARM_MEDIATEK_CPUFREQ || COMPILE_TEST
>> +    select DEVFREQ_GOV_PASSIVE
>> +    help
>> +      This adds a devfreq driver for MediaTek Cache Coherent Interconnect
>> +      which is shared the same regulators with the cpu cluster. It can track
>> +      buck voltages and update a proper CCI frequency. Use the notification
>> +      to get the regulator status.
>> +
>>   config ARM_RK3399_DMC_DEVFREQ
>>       tristate "ARM RK3399 DMC DEVFREQ Driver"
>>       depends on (ARCH_ROCKCHIP && HAVE_ARM_SMCCC) || \
>> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
>> index 0b6be92a25d9..bf40d04928d0 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-$(CONFIG_ARM_IMX_BUS_DEVFREQ)    += imx-bus.o
>>   obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ)    += imx8m-ddrc.o
>> +obj-$(CONFIG_ARM_MEDIATEK_CCI_DEVFREQ)    += mtk-cci-devfreq.o
>>   obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)    += rk3399_dmc.o
>>   obj-$(CONFIG_ARM_SUN8I_A33_MBUS_DEVFREQ)    += sun8i-a33-mbus.o
>>   obj-$(CONFIG_ARM_TEGRA_DEVFREQ)        += tegra30-devfreq.o
>> diff --git a/drivers/devfreq/mtk-cci-devfreq.c b/drivers/devfreq/mtk-cci-devfreq.c
>> new file mode 100644
>> index 000000000000..df42da35b312
>> --- /dev/null
>> +++ b/drivers/devfreq/mtk-cci-devfreq.c
>> @@ -0,0 +1,441 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (C) 2022 MediaTek Inc.
>> + */
>> +
>
> ..snip..
>
>> +};
>> +
>> +static int mtk_ccifreq_probe(struct platform_device *pdev)
>> +{
>> +    struct device *dev = &pdev->dev;
>> +    struct mtk_ccifreq_drv *drv;
>> +    struct devfreq_passive_data *passive_data;
>> +    struct dev_pm_opp *opp;
>> +    unsigned long rate, opp_volt;
>> +    int ret;
>> +
>> +    drv = devm_kzalloc(dev, sizeof(*drv), GFP_KERNEL);
>> +    if (!drv)
>> +        return -ENOMEM;
>> +
>> +    drv->dev = dev;
>> +    drv->soc_data = (const struct mtk_ccifreq_platform_data *)
>> +                of_device_get_match_data(&pdev->dev);
>> +    mutex_init(&drv->reg_lock);
>> +    platform_set_drvdata(pdev, drv);
>> +
>> +    drv->cci_clk = devm_clk_get(dev, "cci");
>> +    if (IS_ERR(drv->cci_clk)) {
>> +        ret = PTR_ERR(drv->cci_clk);
>> +        return dev_err_probe(dev, ret,
>> +                     "failed to get cci clk: %d\n", ret);
>> +    }
>> +
>> +    drv->inter_clk = devm_clk_get(dev, "intermediate");
>> +    if (IS_ERR(drv->inter_clk)) {
>> +        ret = PTR_ERR(drv->inter_clk);
>> +        return dev_err_probe(dev, ret,
>> +                     "failed to get intermediate clk: %d\n", ret);
>> +    }
>> +
>> +    drv->proc_reg = devm_regulator_get_optional(dev, "proc");
>
> In the devicetree binding for this driver, the "proc" regulator is *not* optional,
> but here you're using devm_regulator_get_optional.
>
> If this is not optional, you should use devm_regulator_get() instead.
>
>> +    if (IS_ERR(drv->proc_reg)) {
>> +        ret = PTR_ERR(drv->proc_reg);
>> +        return dev_err_probe(dev, ret,
>> +                     "failed to get proc regulator: %d\n", ret);
>
> There's no need to print ret... dev_err_probe() takes care of that for you already:
> in this case, you're printing the value of ret twice.
>

I agree. better to remove the additional 'ret' printing
from dev_err_probe.

>> +    }
>> +
>> +    ret = regulator_enable(drv->proc_reg);
>
> If you move this call after the devm_regulator_get_optional() call for the sram
> vreg, you will be able to use dev_err_probe for the latter as well.
>
>> +    if (ret) {
>> +        dev_err(dev, "failed to enable proc regulator\n");
>
> Why aren't you using dev_err_probe here, like you've done for the other instances?


dev_err is enough because it means that get to regulator instance
via regulator_get_optional. If error from regulator_enable happen,
it depends on the internal logic of pmic driver.

>
>> +        return ret;
>> +    }
>> +
>> +    drv->sram_reg = devm_regulator_get_optional(dev, "sram");
>> +    if (IS_ERR(drv->sram_reg))
>> +        drv->sram_reg = NULL;
>
> When you use regulator_get_optional() (including the devm_ variant of it), you
> shall return an error, if there's any... that's what the _optional() is for.
>
> if (IS_ERR(drv->sram_reg))
>     return dev_err_probe(dev, PTR_ERR(drv->proc_reg),
>                  "failed to get sram regulator");
>
>> +    else {
>> +        ret = regulator_enable(drv->sram_reg);
>> +        if (ret) {
>> +            dev_err(dev, "failed to enable sram regulator\n");
>> +            goto out_free_resources;
>> +        }
>> +    }
>> +
>
> Regards,
> Angelo
>

Hi Johnson,

Thanks for your work. Before merge, better to remove the
'ret' printing from dev_err_probe above. I'll merge it.


--
Best Regards,
Chanwoo Choi
Samsung Electronics