Re: [PATCH 2/3] devfreq: mediatek: add mt8183 cci devfreq driver

Krzysztof Kozlowski
2022-03-07T21:51:54Z

On 07/03/2022 13:25, Tim Chang wrote:
> This adds a devfreq driver for the Cache Coherent Interconnect (CCI) of
> the Mediatek MT8183.
>
> On 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.
>
> Add need_voltage_tracking variable to platforma data. if true, it
> indicates soc is required to realize the voltage tracking between
> voltage of sram and voltage of cci by software approach. otherwise, the
> voltage tracking is realized by hardware appraoch.
>
> Add the notifier to cci so that it could react after svs driver changes
> opp table of cci.
>
> Signed-off-by: Jia-Wei Chang <jia-wei.chang@mediatek.corp-partner.google.com>
> ---
> drivers/devfreq/Kconfig | 11 +-
> drivers/devfreq/Makefile | 2 +-
> drivers/devfreq/mtk-cci-devfreq.c | 471 ++++++++++++++++++++++++++++++
> 3 files changed, 482 insertions(+), 2 deletions(-)
> create mode 100644 drivers/devfreq/mtk-cci-devfreq.c
>
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index 1ec36ae93f31..a6be3c6b5691 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -110,7 +110,7 @@ config ARM_IMX8M_DDRC_DEVFREQ
>
> config ARM_MT8183_CCI_DEVFREQ
> tristate "MT8183 CCI DEVFREQ Driver"
> - depends on ARM_MEDIATEK_CPUFREQ
> + depends on OF && ARM_MEDIATEK_CPUFREQ

Why do you need that dependency? Isn't your arch already OF-only?

> help
> This adds a devfreq driver for Cache Coherent Interconnect
> of Mediatek MT8183, which is shared the same regulator
> @@ -130,6 +130,15 @@ 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 OF && ARM_MEDIATEK_CPUFREQ
> + help
> + This adds a devfreq driver for Mediatek Cache Coherent Interconnect
> + 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.
> +
> 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 991ef7740759..0493516a16f2 100644
> --- a/drivers/devfreq/Makefile
> +++ b/drivers/devfreq/Makefile
> @@ -11,7 +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-$(CONFIG_ARM_MT8183_CCI_DEVFREQ) += mt8183-cci-devfreq.o
> +obj-$(CONFIG_ARM_MEDIATEK_CCI_DEVFREQ) += mtk-cci-devfreq.o

How is this related? You say in commit subject and description that you
add a devfreq driver. But here you remove some other file...

> obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ) += rk3399_dmc.o
> obj-$(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..986f34689f5c
> --- /dev/null
> +++ b/drivers/devfreq/mtk-cci-devfreq.c
> @@ -0,0 +1,471 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2022 MediaTek Inc.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/devfreq.h>
> +#include <linux/minmax.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_opp.h>
> +#include <linux/regulator/consumer.h>
> +
> +struct mtk_ccifreq_platform_data;

Move struct mtk_ccifreq_platform_data definition here. No need for
forward declaration.

> +
> +struct mtk_ccifreq_drv {
> + struct device *cci_dev;
> + struct devfreq *devfreq;
> + struct regulator *proc_reg;
> + struct regulator *sram_reg;
> + struct clk *cci_clk;
> + struct clk *inter_clk;
> + int inter_voltage;
> + int old_voltage;
> + unsigned long old_freq;
> + struct mutex lock; /* avoid notify and policy race condition */
> + struct notifier_block opp_nb;
> + const struct mtk_ccifreq_platform_data *soc_data;
> +};
> +
> +struct mtk_ccifreq_platform_data {
> + int min_volt_shift;
> + int max_volt_shift;
> + int proc_max_volt;
> + int sram_min_volt;
> + int sram_max_volt;
> + bool need_voltage_tracking;
> +};
> +
> +static int mtk_ccifreq_voltage_tracking(struct mtk_ccifreq_drv *drv, int new_voltage)
> +{
> + const struct mtk_ccifreq_platform_data *soc_data = drv->soc_data;
> + struct regulator *proc_reg = drv->proc_reg;
> + struct regulator *sram_reg = drv->sram_reg;
> + int old_voltage, old_vsram, new_vsram, vsram, voltage, ret;
> +
> + old_voltage = regulator_get_voltage(proc_reg);
> + if (old_voltage < 0) {
> + pr_err("%s: invalid vproc value: %d\n", __func__, old_voltage);
> + return old_voltage;
> + }
> +
> + old_vsram = regulator_get_voltage(sram_reg);
> + if (old_vsram < 0) {
> + pr_err("%s: invalid vsram value: %d\n", __func__, old_vsram);
> + return old_vsram;
> + }
> +
> + new_vsram = clamp(new_voltage + soc_data->min_volt_shift,
> + soc_data->sram_min_volt, soc_data->sram_max_volt);
> +
> + do {
> + if (old_voltage <= new_voltage) {
> + vsram = clamp(old_voltage + soc_data->max_volt_shift,
> + soc_data->sram_min_volt, new_vsram);
> + ret = regulator_set_voltage(sram_reg, vsram,
> + soc_data->sram_max_volt);
> + if (ret)
> + return ret;
> +
> + if (vsram == soc_data->sram_max_volt ||
> + new_vsram == soc_data->sram_min_volt)
> + voltage = new_voltage;
> + else
> + voltage = vsram - soc_data->min_volt_shift;
> +
> + ret = regulator_set_voltage(proc_reg, voltage,
> + soc_data->proc_max_volt);
> + if (ret) {
> + regulator_set_voltage(sram_reg, old_vsram,
> + soc_data->sram_max_volt);
> + return ret;
> + }
> + } else if (old_voltage > new_voltage) {
> + voltage = max(new_voltage,
> + old_vsram - soc_data->max_volt_shift);
> + ret = regulator_set_voltage(proc_reg, voltage,
> + soc_data->proc_max_volt);
> + if (ret)
> + return ret;
> +
> + if (voltage == new_voltage)
> + vsram = new_vsram;
> + else
> + vsram = max(new_vsram,
> + voltage + soc_data->min_volt_shift);
> +
> + ret = regulator_set_voltage(sram_reg, vsram,
> + soc_data->sram_max_volt);
> + if (ret) {
> + regulator_set_voltage(proc_reg, old_voltage,
> + soc_data->proc_max_volt);
> + return ret;
> + }
> + }
> +
> + old_voltage = voltage;
> + old_vsram = vsram;
> + } while (voltage != new_voltage || vsram != new_vsram);
> +
> + return 0;
> +}
> +
> +static int mtk_ccifreq_set_voltage(struct mtk_ccifreq_drv *drv, int voltage)
> +{
> + int ret;
> +
> + if (drv->soc_data->need_voltage_tracking)
> + ret = mtk_ccifreq_voltage_tracking(drv, voltage);
> + else
> + ret = regulator_set_voltage(drv->proc_reg, voltage,
> + drv->soc_data->proc_max_volt);
> +
> + if (!ret)
> + drv->old_voltage = voltage;
> +
> + return ret;
> +}
> +
> +static int mtk_ccifreq_target(struct device *dev, unsigned long *freq,
> + u32 flags)
> +{
> + struct mtk_ccifreq_drv *drv = dev_get_drvdata(dev);
> + struct clk *cci_pll = clk_get_parent(drv->cci_clk);
> + struct dev_pm_opp *opp;
> + unsigned long opp_rate;
> + int voltage, old_voltage, inter_voltage, target_voltage, ret;
> +
> + if (!drv)
> + return -EINVAL;
> +
> + if (drv->old_freq == *freq)
> + return 0;
> +
> + inter_voltage = drv->inter_voltage;
> +
> + opp_rate = *freq;
> + opp = devfreq_recommended_opp(dev, &opp_rate, 1);
> + if (IS_ERR(opp)) {
> + pr_err("cci: failed to find opp for freq: %ld\n", opp_rate);

dev_err() everywhere.

> + return PTR_ERR(opp);
> + }
> + voltage = dev_pm_opp_get_voltage(opp);
> + dev_pm_opp_put(opp);
> +
> + old_voltage = drv->old_voltage;
> + if (old_voltage == 0)
> + old_voltage = regulator_get_voltage(drv->proc_reg);
> + if (old_voltage < 0) {
> + pr_err("cci: invalid vproc value: %d\n", old_voltage);
> + return old_voltage;
> + }
> +
> + mutex_lock(&drv->lock);
> +
> + /* scale up: set voltage first then freq. */
> + target_voltage = max(inter_voltage, voltage);
> + if (old_voltage <= target_voltage) {
> + ret = mtk_ccifreq_set_voltage(drv, target_voltage);
> + if (ret) {
> + pr_err("cci: failed to scale up voltage\n");
> + mtk_ccifreq_set_voltage(drv, old_voltage);
> + mutex_unlock(&drv->lock);
> + return ret;
> + }
> + }
> +
> + /* switch the cci clock to intermediate clock source. */
> + ret = clk_set_parent(drv->cci_clk, drv->inter_clk);
> + if (ret) {
> + pr_err("cci: failed to re-parent cci clock\n");
> + mtk_ccifreq_set_voltage(drv, old_voltage);
> + WARN_ON(1);

Debug code... please clean up your driver.

> + mutex_unlock(&drv->lock);
> + return ret;
> + }
> +
> + /* set the original clock to target rate. */
> + ret = clk_set_rate(cci_pll, *freq);
> + if (ret) {
> + pr_err("cci: failed to set cci pll rate: %d\n", ret);
> + clk_set_parent(drv->cci_clk, cci_pll);
> + mtk_ccifreq_set_voltage(drv, old_voltage);
> + mutex_unlock(&drv->lock);
> + return ret;
> + }
> +
> + /* switch the cci clock back to the original clock source. */
> + ret = clk_set_parent(drv->cci_clk, cci_pll);
> + if (ret) {
> + pr_err("cci: failed to re-parent cci clock\n");
> + mtk_ccifreq_set_voltage(drv, inter_voltage);
> + WARN_ON(1);
> + mutex_unlock(&drv->lock);

Use goto to error handling pattern.

> + return ret;
> + }
> +
> + /*
> + * If the new voltage is lower than the intermediate voltage or the
> + * original voltage, scale down to the new voltage.
> + */
> + if (voltage < inter_voltage || voltage < old_voltage) {
> + ret = mtk_ccifreq_set_voltage(drv, voltage);
> + if (ret) {
> + pr_err("cci: failed to scale down voltage\n");
> + WARN_ON(1);
> + mutex_unlock(&drv->lock);
> + return ret;
> + }
> + }
> +
> + drv->old_freq = *freq;
> + mutex_unlock(&drv->lock);
> +
> + return 0;
> +}
> +
> +static int mtk_ccifreq_opp_notifier(struct notifier_block *nb,
> + unsigned long event, void *data)
> +{
> + struct dev_pm_opp *opp = data;
> + struct mtk_ccifreq_drv *drv;
> + unsigned long freq, volt;
> +
> + drv = container_of(nb, struct mtk_ccifreq_drv, opp_nb);
> +
> + if (event == OPP_EVENT_ADJUST_VOLTAGE) {
> + freq = dev_pm_opp_get_freq(opp);
> +
> + mutex_lock(&drv->lock);
> + /* current opp item is changed */
> + if (freq == drv->old_freq) {
> + volt = dev_pm_opp_get_voltage(opp);
> + mtk_ccifreq_set_voltage(drv, volt);
> + }
> + mutex_unlock(&drv->lock);
> + }
> +
> + return 0;
> +}
> +
> +static struct devfreq_dev_profile mtk_ccifreq_profile = {
> + .target = mtk_ccifreq_target,
> +};
> +
> +static int mtk_ccifreq_probe(struct platform_device *pdev)
> +{
> + struct device *cci_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(cci_dev, sizeof(*drv), GFP_KERNEL);
> + if (!drv)
> + return -ENOMEM;
> +
> + drv->cci_dev = cci_dev;
> + drv->soc_data = (const struct mtk_ccifreq_platform_data *)
> + of_device_get_match_data(&pdev->dev);
> + mutex_init(&drv->lock);
> + platform_set_drvdata(pdev, drv);
> +
> + drv->cci_clk = devm_clk_get(cci_dev, "cci");
> + if (IS_ERR(drv->cci_clk)) {
> + ret = PTR_ERR(drv->cci_clk);
> + return dev_err_probe(cci_dev, ret,
> + "cci: failed to get cci clk: %d\n",
> + ret);
> + }
> +
> + drv->inter_clk = devm_clk_get(cci_dev, "intermediate");
> + if (IS_ERR(drv->inter_clk)) {
> + ret = PTR_ERR(drv->inter_clk);
> + return dev_err_probe(cci_dev, ret,
> + "cci: failed to get intermediate clk: %d\n",
> + ret);
> + }
> +
> + if (drv->soc_data->need_voltage_tracking) {
> + drv->sram_reg = regulator_get_optional(cci_dev, "sram");
> + if (IS_ERR_OR_NULL(drv->sram_reg)) {

NULL pointer cannot be returned.

Best regards,
Krzysztof