Message-ID: <c2026bdf-e796-22ac-c5b3-f022f23c493e@nvidia.com>
Date:   Thu, 8 Mar 2018 23:15:17 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Peter De Schrijver <pdeschrijver@...dia.com>,
        <linux-tegra@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <mturquette@...libre.com>, <sboyd@...eaurora.org>,
        <robh+dt@...nel.org>, <mark.rutland@....com>,
        <devicetree@...r.kernel.org>, <lgirdwood@...il.com>,
        <broonie@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 06/11] clk: tegra: dfll: support PWM regulator control


On 06/02/18 16:34, Peter De Schrijver wrote:
> The DFLL can directly generate a PWM signal to control the regulator IC
> rather then sending i2c messages. This patch adds support for this mode.
> In this mode the hardware LUT is not used and also there is no regulator
> object involved because there is no way to control the regulator voltage
> without also changing the DFLL output frequency. Also the register debugfs
> file is slightly reworked to only show the i2c registers when i2c mode is
> in use. As there is no regulator object for the PWM regulator, its step and
> offset values are retrieved from DT instead.

It is unclear to me why we bother creating the LUT for PWM if it is not
used? Is this for debug to get an approximation? Why do we do this?

> Signed-off-by: Peter De Schrijver <pdeschrijver@...dia.com>
> ---
>  drivers/clk/tegra/clk-dfll.c               | 398 ++++++++++++++++++++++++++---
>  drivers/clk/tegra/clk-tegra124-dfll-fcpu.c |  23 +-
>  2 files changed, 382 insertions(+), 39 deletions(-)
> 
> diff --git a/drivers/clk/tegra/clk-dfll.c b/drivers/clk/tegra/clk-dfll.c
> index fa97763..228edb4 100644
> --- a/drivers/clk/tegra/clk-dfll.c
> +++ b/drivers/clk/tegra/clk-dfll.c
> @@ -243,6 +243,12 @@ enum dfll_tune_range {
>  	DFLL_TUNE_LOW = 1,
>  };
>  
> +
> +enum tegra_dfll_pmu_if {
> +	TEGRA_DFLL_PMU_I2C = 0,
> +	TEGRA_DFLL_PMU_PWM = 1,
> +};
> +
>  /**
>   * struct dfll_rate_req - target DFLL rate request data
>   * @rate: target frequency, after the postscaling
> @@ -294,17 +300,25 @@ struct tegra_dfll {
>  	u32				ci;
>  	u32				cg;
>  	bool				cg_scale;
> +	u32				reg_init_uV;
>  
>  	/* I2C interface parameters */
>  	u32				i2c_fs_rate;
>  	u32				i2c_reg;
>  	u32				i2c_slave_addr;
>  
> -	/* i2c_lut array entries are regulator framework selectors */
> +	/* lut array entries are regulator framework selectors or PWM values*/
>  	unsigned int			i2c_lut[MAX_DFLL_VOLTAGES];
>  	unsigned int			lut_uv[MAX_DFLL_VOLTAGES];
>  	int				lut_size;
>  	u8				lut_bottom, lut_min, lut_max, lut_safe;
> +
> +	/* PWM interface */
> +	enum tegra_dfll_pmu_if		pmu_if;
> +	unsigned long			pwm_rate;
> +	struct pinctrl			*pwm_pin;
> +	struct pinctrl_state		*pwm_enable_state;
> +	struct pinctrl_state		*pwm_disable_state;
>  };
>  
>  #define clk_hw_to_dfll(_hw) container_of(_hw, struct tegra_dfll, dfll_clk_hw)
> @@ -491,6 +505,36 @@ static void dfll_set_mode(struct tegra_dfll *td,
>  }
>  
>  /*
> + * DVCO rate control
> + */
> +
> +static unsigned long get_dvco_rate_below(struct tegra_dfll *td, u8 out_min)
> +{
> +	struct dev_pm_opp *opp;
> +	unsigned long rate, prev_rate;
> +	int uv, min_uv;
> +
> +	min_uv = td->lut_uv[out_min];
> +	for (rate = 0, prev_rate = 0; ; rate++) {
> +		rcu_read_lock();
> +		opp = dev_pm_opp_find_freq_ceil(td->soc->dev, &rate);
> +		if (IS_ERR(opp)) {
> +			rcu_read_unlock();
> +			break;
> +		}
> +		uv = dev_pm_opp_get_voltage(opp);
> +		rcu_read_unlock();
> +
> +		if (uv && uv > min_uv)
> +			return prev_rate;
> +
> +		prev_rate = rate;
> +	}
> +
> +	return prev_rate;
> +}
> +
> +/*
>   * DFLL-to-I2C controller interface
>   */
>  
> @@ -519,6 +563,119 @@ static int dfll_i2c_set_output_enabled(struct tegra_dfll *td, bool enable)
>  	return 0;
>  }
>  
> +
> +/*
> + * DFLL-to-PWM controller interface
> + */
> +
> +/**
> + * dfll_pwm_set_output_enabled - enable/disable PWM voltage requests
> + * @td: DFLL instance
> + * @enable: whether to enable or disable the PWM voltage requests
> + *
> + * Set the master enable control for PWM control value updates. If disabled,
> + * then the PWM signal is not driven. Also configure the PWM output pad
> + * to the appropriate state.
> + */
> +static int dfll_pwm_set_output_enabled(struct tegra_dfll *td, bool enable)
> +{
> +	int ret;
> +	u32 val, div;
> +
> +	if (enable) {
> +		ret = pinctrl_select_state(td->pwm_pin, td->pwm_enable_state);
> +		if (ret < 0) {
> +			dev_err(td->dev, "setting enable state failed\n");
> +			return ret;
> +		}
> +		val = dfll_readl(td, DFLL_OUTPUT_CFG);
> +		val &= ~DFLL_OUTPUT_CFG_PWM_DIV_MASK;
> +		div = DIV_ROUND_UP(td->ref_rate, td->pwm_rate);
> +		val |= (div << DFLL_OUTPUT_CFG_PWM_DIV_SHIFT)
> +				& DFLL_OUTPUT_CFG_PWM_DIV_MASK;
> +		dfll_writel(td, val, DFLL_OUTPUT_CFG);
> +		dfll_wmb(td);
> +
> +		val |= DFLL_OUTPUT_CFG_PWM_ENABLE;
> +		dfll_writel(td, val, DFLL_OUTPUT_CFG);
> +		dfll_wmb(td);
> +	} else {
> +		ret = pinctrl_select_state(td->pwm_pin, td->pwm_disable_state);
> +		if (ret < 0)
> +			dev_warn(td->dev, "setting disable state failed\n");
> +
> +		val = dfll_readl(td, DFLL_OUTPUT_CFG);
> +		val &= ~DFLL_OUTPUT_CFG_PWM_ENABLE;
> +		dfll_writel(td, val, DFLL_OUTPUT_CFG);
> +		dfll_wmb(td);
> +	}
> +
> +	return 0;
> +}
> +/**
> + * dfll_set_force_output_value - set fixed value for force output
> + * @td: DFLL instance
> + * @out_val: value to force output
> + *
> + * Set the fixed value for force output, DFLL will output this value when
> + * force output is enabled.
> + */
> +static u32 dfll_set_force_output_value(struct tegra_dfll *td, u8 out_val)
> +{
> +	u32 val = dfll_readl(td, DFLL_OUTPUT_FORCE);
> +
> +	val &= ~OUT_MASK;
> +	val = (val & DFLL_OUTPUT_FORCE_ENABLE) | (out_val & OUT_MASK);

This masking of out_val is not needed as you check in dfll_force_output().

> +	dfll_writel(td, val, DFLL_OUTPUT_FORCE);
> +	dfll_wmb(td);
> +
> +	return dfll_readl(td, DFLL_OUTPUT_FORCE);
> +}
> +
> +/**
> + * dfll_set_force_output_enabled - enable/disable force output
> + * @td: DFLL instance
> + * @enable: whether to enable or disable the force output
> + *
> + * Set the enable control for fouce output with fixed value.
> + */
> +static void dfll_set_force_output_enabled(struct tegra_dfll *td, bool enable)
> +{
> +	u32 val = dfll_readl(td, DFLL_OUTPUT_FORCE);
> +
> +	if (enable)
> +		val |= DFLL_OUTPUT_FORCE_ENABLE;
> +	else
> +		val &= ~DFLL_OUTPUT_FORCE_ENABLE;
> +
> +	dfll_writel(td, val, DFLL_OUTPUT_FORCE);
> +	dfll_wmb(td);
> +}
> +
> +/**
> + * dfll_i2c_set_output_enabled - enable/disable I2C PMIC voltage requests
> + * @td: DFLL instance
> + * @enable: whether to enable or disable the I2C voltage requests
> + *
> + * Set the master enable control for I2C control value updates. If disabled,
> + * then I2C control messages are inhibited, regardless of the DFLL mode.
> + */

The above description needs correcting.

> +static int dfll_force_output(struct tegra_dfll *td, unsigned int out_sel)
> +{
> +	u32 val;
> +
> +	if (out_sel > OUT_MASK)
> +		return -EINVAL;
> +
> +	val = dfll_set_force_output_value(td, out_sel);
> +	if ((td->mode < DFLL_CLOSED_LOOP) &&
> +	    !(val & DFLL_OUTPUT_FORCE_ENABLE)) {
> +		dfll_set_force_output_enabled(td, true);
> +	}
> +
> +	return 0;
> +}
> +
>  /**
>   * dfll_load_lut - load the voltage lookup table
>   * @td: struct tegra_dfll *
> @@ -599,20 +756,50 @@ static void dfll_init_out_if(struct tegra_dfll *td)
>  	td->lut_max = td->lut_size - 1;
>  	td->lut_safe = td->lut_min + (td->lut_min < td->lut_max ? 1 : 0);
>  
> -	dfll_i2c_writel(td, 0, DFLL_OUTPUT_CFG);
> -	val = (td->lut_safe << DFLL_OUTPUT_CFG_SAFE_SHIFT) |
> -		(td->lut_max << DFLL_OUTPUT_CFG_MAX_SHIFT) |
> -		(td->lut_min << DFLL_OUTPUT_CFG_MIN_SHIFT);
> -	dfll_i2c_writel(td, val, DFLL_OUTPUT_CFG);
> -	dfll_i2c_wmb(td);
> -
> -	dfll_writel(td, 0, DFLL_OUTPUT_FORCE);
> -	dfll_i2c_writel(td, 0, DFLL_INTR_EN);
> -	dfll_i2c_writel(td, DFLL_INTR_MAX_MASK | DFLL_INTR_MIN_MASK,
> -			DFLL_INTR_STS);
> -
> -	dfll_load_i2c_lut(td);
> -	dfll_init_i2c_if(td);
> +	if (td->pmu_if == TEGRA_DFLL_PMU_PWM) {
> +		int vinit = td->reg_init_uV;
> +		int vstep = td->soc->alignment.step_uv;
> +		int vmin = td->lut_uv[0];
> +
> +		/* clear DFLL_OUTPUT_CFG before setting new value */
> +		dfll_writel(td, 0, DFLL_OUTPUT_CFG);
> +		dfll_wmb(td);
> +
> +		val = dfll_readl(td, DFLL_OUTPUT_CFG);
> +		val |= (td->lut_safe << DFLL_OUTPUT_CFG_SAFE_SHIFT) |
> +		       (td->lut_max << DFLL_OUTPUT_CFG_MAX_SHIFT) |
> +		       (td->lut_min << DFLL_OUTPUT_CFG_MIN_SHIFT);
> +		dfll_writel(td, val, DFLL_OUTPUT_CFG);
> +		dfll_wmb(td);
> +
> +		dfll_writel(td, 0, DFLL_OUTPUT_FORCE);
> +		dfll_i2c_writel(td, 0, DFLL_INTR_EN);
> +		dfll_i2c_writel(td, DFLL_INTR_MAX_MASK | DFLL_INTR_MIN_MASK,
> +				DFLL_INTR_STS);
> +
> +		/* set initial voltage */
> +		if ((vinit >= vmin) && vstep) {
> +			unsigned int vsel;
> +
> +			vsel = DIV_ROUND_UP((vinit - vmin), vstep);
> +			dfll_force_output(td, vsel);
> +		}
> +	} else {
> +		dfll_i2c_writel(td, 0, DFLL_OUTPUT_CFG);
> +		val = (td->lut_safe << DFLL_OUTPUT_CFG_SAFE_SHIFT) |
> +			(td->lut_max << DFLL_OUTPUT_CFG_MAX_SHIFT) |
> +			(td->lut_min << DFLL_OUTPUT_CFG_MIN_SHIFT);
> +		dfll_i2c_writel(td, val, DFLL_OUTPUT_CFG);
> +		dfll_i2c_wmb(td);
> +
> +		dfll_writel(td, 0, DFLL_OUTPUT_FORCE);
> +		dfll_i2c_writel(td, 0, DFLL_INTR_EN);
> +		dfll_i2c_writel(td, DFLL_INTR_MAX_MASK | DFLL_INTR_MIN_MASK,
> +				DFLL_INTR_STS);
> +
> +		dfll_load_i2c_lut(td);
> +		dfll_init_i2c_if(td);
> +	}
>  }
>  
>  /*
> @@ -864,9 +1051,14 @@ static int dfll_lock(struct tegra_dfll *td)
>  			return -EINVAL;
>  		}
>  
> -		dfll_i2c_set_output_enabled(td, true);
> +		if (td->pmu_if == TEGRA_DFLL_PMU_PWM)
> +			dfll_pwm_set_output_enabled(td, true);
> +		else
> +			dfll_i2c_set_output_enabled(td, true);
> +
>  		dfll_set_mode(td, DFLL_CLOSED_LOOP);
>  		dfll_set_frequency_request(td, req);
> +		dfll_set_force_output_enabled(td, false);
>  		return 0;
>  
>  	default:
> @@ -890,7 +1082,10 @@ static int dfll_unlock(struct tegra_dfll *td)
>  	case DFLL_CLOSED_LOOP:
>  		dfll_set_open_loop_config(td);
>  		dfll_set_mode(td, DFLL_OPEN_LOOP);
> -		dfll_i2c_set_output_enabled(td, false);
> +		if (td->pmu_if == TEGRA_DFLL_PMU_PWM)
> +			dfll_pwm_set_output_enabled(td, false);
> +		else
> +			dfll_i2c_set_output_enabled(td, false);
>  		return 0;
>  
>  	case DFLL_OPEN_LOOP:
> @@ -1172,15 +1367,17 @@ static int attr_registers_show(struct seq_file *s, void *data)
>  		seq_printf(s, "[0x%02x] = 0x%08x\n", offs,
>  			   dfll_i2c_readl(td, offs));
>  
> -	seq_puts(s, "\nINTEGRATED I2C CONTROLLER REGISTERS:\n");
> -	offs = DFLL_I2C_CLK_DIVISOR;
> -	seq_printf(s, "[0x%02x] = 0x%08x\n", offs,
> -		   __raw_readl(td->i2c_controller_base + offs));
> -
> -	seq_puts(s, "\nLUT:\n");
> -	for (offs = 0; offs <  4 * MAX_DFLL_VOLTAGES; offs += 4)
> +	if (td->pmu_if == TEGRA_DFLL_PMU_I2C) {
> +		seq_puts(s, "\nINTEGRATED I2C CONTROLLER REGISTERS:\n");
> +		offs = DFLL_I2C_CLK_DIVISOR;
>  		seq_printf(s, "[0x%02x] = 0x%08x\n", offs,
> -			   __raw_readl(td->lut_base + offs));
> +			   __raw_readl(td->i2c_controller_base + offs));
> +
> +		seq_puts(s, "\nLUT:\n");
> +		for (offs = 0; offs <  4 * MAX_DFLL_VOLTAGES; offs += 4)
> +			seq_printf(s, "[0x%02x] = 0x%08x\n", offs,
> +				   __raw_readl(td->lut_base + offs));
> +	}
>  
>  	return 0;
>  }
> @@ -1289,6 +1486,9 @@ static int dfll_init_clks(struct tegra_dfll *td)
>  		return PTR_ERR(td->soc_clk);
>  	}
>  
> +	if (td->pmu_if != TEGRA_DFLL_PMU_I2C)
> +		return 0;
> +
>  	td->i2c_clk = devm_clk_get(td->dev, "i2c");
>  	if (IS_ERR(td->i2c_clk)) {
>  		dev_err(td->dev, "missing i2c clock\n");
> @@ -1420,6 +1620,52 @@ static int find_vdd_map_entry_min(struct tegra_dfll *td, int uV)
>  	return -EINVAL;
>  }
>  
> +/*
> + * Look-up table in h/w is ignored when PWM is used as DFLL interface to PMIC.
> + * In this case closed loop output is controlling duty cycle directly. The s/w
> + * look-up that maps PWM duty cycle to voltage is still built by this function.

Why?

> + */
> +static int dfll_build_lut_pwm(struct tegra_dfll *td, int v_max)
> +{
> +	int i, reg_volt;
> +	unsigned long rate;
> +	u8 lut_bottom = MAX_DFLL_VOLTAGES;
> +	int v_min = td->soc->cvb->min_millivolts * 1000;
> +
> +	for (i = 0; i < MAX_DFLL_VOLTAGES; i++) {
> +		reg_volt = td->lut_uv[i];
> +
> +		/* since opp voltage is exact mv */
> +		reg_volt = (reg_volt / 1000) * 1000;
> +		if (reg_volt > v_max)
> +			break;
> +
> +		if ((lut_bottom == MAX_DFLL_VOLTAGES) && (reg_volt >= v_min))
> +			lut_bottom = i;
> +	}
> +
> +	/* determine voltage boundaries */
> +	td->lut_size = i;
> +	if ((lut_bottom == MAX_DFLL_VOLTAGES) ||
> +	    (lut_bottom + 1 >= td->lut_size)) {
> +		dev_err(td->dev, "no voltage above DFLL minimum %d mV\n",
> +			td->soc->cvb->min_millivolts);
> +		return -EINVAL;
> +	}
> +	td->lut_bottom = lut_bottom;
> +
> +	/* determine rate boundaries */
> +	rate = get_dvco_rate_below(td, td->lut_bottom);
> +	if (!rate) {
> +		dev_err(td->dev, "no opp below DFLL minimum voltage %d mV\n",
> +			td->soc->cvb->min_millivolts);
> +		return -EINVAL;
> +	}
> +	td->dvco_rate_min = rate;
> +
> +	return 0;
> +}
> +
>  /**
>   * dfll_build_i2c_lut - build the I2C voltage register lookup table
>   * @td: DFLL instance
> @@ -1432,10 +1678,10 @@ static int find_vdd_map_entry_min(struct tegra_dfll *td, int uV)
>   *
>   * On success, fills in td->i2c_lut and returns 0, or -err on failure.
>   */
> -static int dfll_build_i2c_lut(struct tegra_dfll *td)
> +static int dfll_build_i2c_lut(struct tegra_dfll *td, int v_max)
>  {
>  	int ret = -EINVAL;
> -	int j, v, v_max, v_opp;
> +	int j, v, v_opp;
>  	int selector;
>  	unsigned long rate;
>  	struct dev_pm_opp *opp;
> @@ -1508,6 +1754,30 @@ static int dfll_build_i2c_lut(struct tegra_dfll *td)
>  	return ret;
>  }
>  
> +static int dfll_build_lut(struct tegra_dfll *td)
> +{
> +	unsigned long rate;
> +	struct dev_pm_opp *opp;
> +	int v_max;
> +
> +	rcu_read_lock();
> +
> +	rate = ULONG_MAX;
> +	opp = dev_pm_opp_find_freq_floor(td->soc->dev, &rate);
> +	if (IS_ERR(opp)) {
> +		dev_err(td->dev, "couldn't get vmax opp, empty opp table?\n");
> +		return -EINVAL;
> +	}
> +	v_max = dev_pm_opp_get_voltage(opp);
> +
> +	rcu_read_unlock();
> +
> +	if (td->pmu_if == TEGRA_DFLL_PMU_PWM)
> +		return dfll_build_lut_pwm(td, v_max);
> +	else
> +		return dfll_build_i2c_lut(td, v_max);
> +}
> +
>  /**
>   * read_dt_param - helper function for reading required parameters from the DT
>   * @td: DFLL instance
> @@ -1566,11 +1836,54 @@ static int dfll_fetch_i2c_params(struct tegra_dfll *td)
>  	}
>  	td->i2c_reg = vsel_reg;
>  
> -	ret = dfll_build_i2c_lut(td);
> -	if (ret) {
> -		dev_err(td->dev, "couldn't build I2C LUT\n");
> +	return 0;
> +}
> +
> +static int dfll_fetch_pwm_params(struct tegra_dfll *td)
> +{
> +	int ret, i;
> +	u32 pwm_period;
> +
> +	if (!td->soc->alignment.step_uv || !td->soc->alignment.offset_uv) {
> +		dev_err(td->dev, "Missing step or alignment info for PWM regulator");
> +		return -EINVAL;
> +	}
> +	for (i = 0; i < MAX_DFLL_VOLTAGES; i++)
> +		td->lut_uv[i] = td->soc->alignment.offset_uv +
> +				i * td->soc->alignment.step_uv;
> +
> +	ret = read_dt_param(td, "nvidia,init-uv", &td->reg_init_uV);
> +	if (!ret) {
> +		dev_err(td->dev, "couldn't get initialized voltage\n");
> +		return ret;
> +	}
> +
> +	ret = read_dt_param(td, "nvidia,pwm-period", &pwm_period);
> +	if (!ret) {
> +		dev_err(td->dev, "couldn't get PWM period\n");
>  		return ret;
>  	}
> +	td->pwm_rate = (NSEC_PER_SEC / pwm_period) * (MAX_DFLL_VOLTAGES - 1);

Do we need to check that this pwm_rate is not too big so we don't end up
with a bad value in dfll_pwm_set_output_enabled()? If this pwm_rate is
not updated and neither is ref_rate, can we not just store the divisor
so we can use in dfll_pwm_set_output_enabled()?

Cheers
Jon

-- 
nvpublic

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