Re: [PATCH v7 04/16] clk: tegra: Add functions for parsing CVB tables

[Peter De Schrijver]

On Thu, Jan 08, 2015 at 03:22:07PM +0200, Mikko Perttunen wrote:
> From: Tuomas Tynkkynen <ttynkkynen@xxxxxxxxxx>
> 
> Tegra CVB tables encode the relationship between operating voltage
> and optimal frequency as a function of the so-called speedo value.
> The speedo value is written to the on-chip fuses at the factory,
> which allows the voltage-frequency operating points to be calculated
> on an per-chip basis.
> 
> Add utility functions to parse the Tegra-specific tables and export the
> voltage-frequency pairs to the generic OPP framework for other drivers
> to use.
> 
> Signed-off-by: Tuomas Tynkkynen <ttynkkynen@xxxxxxxxxx>
> Signed-off-by: Mikko Perttunen <mikko.perttunen@xxxxxxxx>
Acked-By: Peter De Schrijver <pdeschrijver@xxxxxxxxxx>

> ---
>  arch/arm/mach-tegra/Kconfig |   1 +
>  drivers/clk/tegra/cvb.c     | 133 ++++++++++++++++++++++++++++++++++++++++++++
>  drivers/clk/tegra/cvb.h     |  67 ++++++++++++++++++++++
>  3 files changed, 201 insertions(+)
>  create mode 100644 drivers/clk/tegra/cvb.c
>  create mode 100644 drivers/clk/tegra/cvb.h
> 
> diff --git a/arch/arm/mach-tegra/Kconfig b/arch/arm/mach-tegra/Kconfig
> index d0be9a1..6c2f628 100644
> --- a/arch/arm/mach-tegra/Kconfig
> +++ b/arch/arm/mach-tegra/Kconfig
> @@ -8,6 +8,7 @@ menuconfig ARCH_TEGRA
>  	select HAVE_ARM_SCU if SMP
>  	select HAVE_ARM_TWD if SMP
>  	select PINCTRL
> +	select PM_OPP
>  	select ARCH_HAS_RESET_CONTROLLER
>  	select RESET_CONTROLLER
>  	select SOC_BUS
> diff --git a/drivers/clk/tegra/cvb.c b/drivers/clk/tegra/cvb.c
> new file mode 100644
> index 0000000..69c74ee
> --- /dev/null
> +++ b/drivers/clk/tegra/cvb.c
> @@ -0,0 +1,133 @@
> +/*
> + * Utility functions for parsing Tegra CVB voltage tables
> + *
> + * Copyright (C) 2012-2014 NVIDIA Corporation.  All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + */
> +#include <linux/err.h>
> +#include <linux/kernel.h>
> +#include <linux/pm_opp.h>
> +
> +#include "cvb.h"
> +
> +/* cvb_mv = ((c2 * speedo / s_scale + c1) * speedo / s_scale + c0) */
> +static inline int get_cvb_voltage(int speedo, int s_scale,
> +				  const struct cvb_coefficients *cvb)
> +{
> +	int mv;
> +
> +	/* apply only speedo scale: output mv = cvb_mv * v_scale */
> +	mv = DIV_ROUND_CLOSEST(cvb->c2 * speedo, s_scale);
> +	mv = DIV_ROUND_CLOSEST((mv + cvb->c1) * speedo, s_scale) + cvb->c0;
> +	return mv;
> +}
> +
> +static int round_cvb_voltage(int mv, int v_scale,
> +			     const struct rail_alignment *align)
> +{
> +	/* combined: apply voltage scale and round to cvb alignment step */
> +	int uv;
> +	int step = (align->step_uv ? : 1000) * v_scale;
> +	int offset = align->offset_uv * v_scale;
> +
> +	uv = max(mv * 1000, offset) - offset;
> +	uv = DIV_ROUND_UP(uv, step) * align->step_uv + align->offset_uv;
> +	return uv / 1000;
> +}
> +
> +enum {
> +	DOWN,
> +	UP
> +};
> +
> +static int round_voltage(int mv, const struct rail_alignment *align, int up)
> +{
> +	if (align->step_uv) {
> +		int uv;
> +
> +		uv = max(mv * 1000, align->offset_uv) - align->offset_uv;
> +		uv = (uv + (up ? align->step_uv - 1 : 0)) / align->step_uv;
> +		return (uv * align->step_uv + align->offset_uv) / 1000;
> +	}
> +	return mv;
> +}
> +
> +static int build_opp_table(const struct cvb_table *d,
> +			   int speedo_value,
> +			   unsigned long max_freq,
> +			   struct device *opp_dev)
> +{
> +	int i, ret, dfll_mv, min_mv, max_mv;
> +	const struct cvb_table_freq_entry *table = NULL;
> +	const struct rail_alignment *align = &d->alignment;
> +
> +	min_mv = round_voltage(d->min_millivolts, align, UP);
> +	max_mv = round_voltage(d->max_millivolts, align, DOWN);
> +
> +	for (i = 0; i < MAX_DVFS_FREQS; i++) {
> +		table = &d->cvb_table[i];
> +		if (!table->freq || (table->freq > max_freq))
> +			break;
> +
> +		dfll_mv = get_cvb_voltage(
> +			speedo_value, d->speedo_scale, &table->coefficients);
> +		dfll_mv = round_cvb_voltage(dfll_mv, d->voltage_scale, align);
> +		dfll_mv = clamp(dfll_mv, min_mv, max_mv);
> +
> +		ret = dev_pm_opp_add(opp_dev, table->freq, dfll_mv * 1000);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * tegra_cvb_build_opp_table - build OPP table from Tegra CVB tables
> + * @cvb_tables: array of CVB tables
> + * @sz: size of the previously mentioned array
> + * @process_id: process id of the HW module
> + * @speedo_id: speedo id of the HW module
> + * @speedo_value: speedo value of the HW module
> + * @max_rate: highest safe clock rate
> + * @opp_dev: the struct device * for which the OPP table is built
> + *
> + * On Tegra, a CVB table encodes the relationship between operating voltage
> + * and safe maximal frequency for a given module (e.g. GPU or CPU). This
> + * function calculates the optimal voltage-frequency operating points
> + * for the given arguments and exports them via the OPP library for the
> + * given @opp_dev. Returns a pointer to the struct cvb_table that matched
> + * or an ERR_PTR on failure.
> + */
> +const struct cvb_table *tegra_cvb_build_opp_table(
> +		const struct cvb_table *cvb_tables,
> +		size_t sz, int process_id,
> +		int speedo_id, int speedo_value,
> +		unsigned long max_rate,
> +		struct device *opp_dev)
> +{
> +	int i, ret;
> +
> +	for (i = 0; i < sz; i++) {
> +		const struct cvb_table *d = &cvb_tables[i];
> +
> +		if (d->speedo_id != -1 && d->speedo_id != speedo_id)
> +			continue;
> +		if (d->process_id != -1 && d->process_id != process_id)
> +			continue;
> +
> +		ret = build_opp_table(d, speedo_value, max_rate, opp_dev);
> +		return ret ? ERR_PTR(ret) : d;
> +	}
> +
> +	return ERR_PTR(-EINVAL);
> +}
> diff --git a/drivers/clk/tegra/cvb.h b/drivers/clk/tegra/cvb.h
> new file mode 100644
> index 0000000..f62cdc4
> --- /dev/null
> +++ b/drivers/clk/tegra/cvb.h
> @@ -0,0 +1,67 @@
> +/*
> + * Utility functions for parsing Tegra CVB voltage tables
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + */
> +
> +#ifndef __DRIVERS_CLK_TEGRA_CVB_H
> +#define __DRIVERS_CLK_TEGRA_CVB_H
> +
> +#include <linux/types.h>
> +
> +struct device;
> +
> +#define MAX_DVFS_FREQS	40
> +
> +struct rail_alignment {
> +	int offset_uv;
> +	int step_uv;
> +};
> +
> +struct cvb_coefficients {
> +	int c0;
> +	int c1;
> +	int c2;
> +};
> +
> +struct cvb_table_freq_entry {
> +	unsigned long freq;
> +	struct cvb_coefficients coefficients;
> +};
> +
> +struct cvb_cpu_dfll_data {
> +	u32 tune0_low;
> +	u32 tune0_high;
> +	u32 tune1;
> +};
> +
> +struct cvb_table {
> +	int speedo_id;
> +	int process_id;
> +
> +	int min_millivolts;
> +	int max_millivolts;
> +	struct rail_alignment alignment;
> +
> +	int speedo_scale;
> +	int voltage_scale;
> +	struct cvb_table_freq_entry cvb_table[MAX_DVFS_FREQS];
> +	struct cvb_cpu_dfll_data cpu_dfll_data;
> +};
> +
> +const struct cvb_table *tegra_cvb_build_opp_table(
> +		const struct cvb_table *cvb_tables,
> +		size_t sz, int process_id,
> +		int speedo_id, int speedo_value,
> +		unsigned long max_rate,
> +		struct device *opp_dev);
> +
> +#endif
> -- 
> 2.2.1
> 
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