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Date:   Mon, 13 May 2019 00:16:12 +0200
From:   =?utf-8?Q?Ond=C5=99ej?= Jirman <megous@megous.com>
To:     Yangtao Li <tiny.windzz@gmail.com>
Cc:     rui.zhang@intel.com, edubezval@gmail.com,
        daniel.lezcano@linaro.org, robh+dt@kernel.org,
        mark.rutland@arm.com, maxime.ripard@bootlin.com, wens@csie.org,
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        mchehab+samsung@kernel.org, gregkh@linuxfoundation.org,
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        paulmck@linux.ibm.com, andy.gross@linaro.org, olof@lixom.net,
        bjorn.andersson@linaro.org, jagan@amarulasolutions.com,
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        enric.balletbo@collabora.com, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-pm@vger.kernel.org
Subject: Re: [PATCH 2/3] thermal: sun50i: add thermal driver for h6
Message-ID: <20190512221612.ubmknvim4utnqpl4@core.my.home>
Mail-Followup-To: Yangtao Li <tiny.windzz@gmail.com>, rui.zhang@intel.com,
        edubezval@gmail.com, daniel.lezcano@linaro.org, robh+dt@kernel.org,
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        mchehab+samsung@kernel.org, gregkh@linuxfoundation.org,
        Jonathan.Cameron@huawei.com, nicolas.ferre@microchip.com,
        paulmck@linux.ibm.com, andy.gross@linaro.org, olof@lixom.net,
        bjorn.andersson@linaro.org, jagan@amarulasolutions.com,
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References: <20190512082614.9045-1-tiny.windzz@gmail.com>
 <20190512082614.9045-3-tiny.windzz@gmail.com>
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Hello Yangtao,

On Sun, May 12, 2019 at 04:26:13AM -0400, Yangtao Li wrote:
> diff --git a/drivers/thermal/sun50i_thermal.c b/drivers/thermal/sun50i_thermal.c
> new file mode 100644
> index 000000000000..3bdb3677b3d4
> --- /dev/null
> +++ b/drivers/thermal/sun50i_thermal.c
> @@ -0,0 +1,357 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Thermal sensor driver for Allwinner SOC
> + * Copyright (C) 2019 Yangtao Li
> + *
> + * Based on the work of Icenowy Zheng <icenowy@aosc.io>
> + * Based on the work of Ondrej Jirman <megous@megous.com>
> + * Based on the work of Josef Gajdusek <atx@atx.name>
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/nvmem-consumer.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/reset.h>
> +#include <linux/slab.h>
> +#include <linux/thermal.h>
> +
> +#define MAX_SENSOR_NUM	4
> +
> +#define FT_TEMP_MASK				GENMASK(11, 0)
> +#define TEMP_CALIB_MASK				GENMASK(11, 0)
> +#define TEMP_TO_REG				672
> +#define CALIBRATE_DEFAULT			0x800
> +
> +#define SUN50I_THS_CTRL0			0x00
> +#define SUN50I_H6_THS_ENABLE			0x04
> +#define SUN50I_H6_THS_PC			0x08
> +#define SUN50I_H6_THS_MFC			0x30
> +#define SUN50I_H6_TEMP_CALIB			0xa0
> +#define SUN50I_H6_TEMP_DATA			0xc0
> +
> +#define SUN50I_THS_CTRL0_T_ACQ(x)		((GENMASK(15, 0) & (x)) << 16)
> +#define SUN50I_THS_FILTER_EN			BIT(2)
> +#define SUN50I_THS_FILTER_TYPE(x)		(GENMASK(1, 0) & (x))
> +#define SUN50I_H6_THS_PC_TEMP_PERIOD(x)		((GENMASK(19, 0) & (x)) << 12)
> +
> +/* millidegree celsius */
> +#define SUN50I_H6_FT_DEVIATION			7000
> +
> +struct tsens_device;
> +
> +struct tsensor {
> +	struct tsens_device		*tmdev;
> +	struct thermal_zone_device	*tzd;
> +	int				id;
> +};
> +
> +struct sun50i_thermal_chip {
> +	int	sensor_num;
> +	int	offset;
> +	int	scale;
> +	int	ft_deviation;
> +	int	temp_calib_base;
> +	int	temp_data_base;
> +	int	(*enable)(struct tsens_device *tmdev);
> +	int	(*disable)(struct tsens_device *tmdev);
> +};
> +
> +
> +struct tsens_device {
> +	const struct sun50i_thermal_chip	*chip;
> +	struct device				*dev;
> +	struct regmap				*regmap;
> +	struct reset_control			*reset;
> +	struct clk				*bus_clk;
> +	struct tsensor				sensor[MAX_SENSOR_NUM];
> +};
> +
> +/* Temp Unit: millidegree Celsius */
> +static int tsens_reg2temp(struct tsens_device *tmdev,
> +			      int reg)

Please name all functions so that they are more clearly identifiable
in stack traces as belonging to this driver. For example:

  sun8i_ths_reg2temp

The same applies for all tsens_* functions below. tsens_* is too
generic.

> +{
> +	return (reg + tmdev->chip->offset) * tmdev->chip->scale;
> +}
> +
> +static int tsens_get_temp(void *data, int *temp)
> +{
> +	struct tsensor *s = data;
> +	struct tsens_device *tmdev = s->tmdev;
> +	int val;
> +
> +	regmap_read(tmdev->regmap, tmdev->chip->temp_data_base +
> +		    0x4 * s->id, &val);
> +
> +	if (unlikely(val == 0))
> +		return -EBUSY;
> +
> +	*temp = tsens_reg2temp(tmdev, val);
> +	if (tmdev->chip->ft_deviation)
> +		*temp += tmdev->chip->ft_deviation;
> +
> +	return 0;
> +}
> +
> +static const struct thermal_zone_of_device_ops tsens_ops = {
> +	.get_temp = tsens_get_temp,
> +};
> +
> +static const struct regmap_config config = {
> +	.reg_bits = 32,
> +	.val_bits = 32,
> +	.reg_stride = 4,
> +	.fast_io = true,
> +};
> +
> +static int tsens_init(struct tsens_device *tmdev)
> +{
> +	struct device *dev = tmdev->dev;
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct resource *mem;
> +	void __iomem *base;
> +
> +	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	base = devm_ioremap_resource(dev, mem);
> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	tmdev->regmap = devm_regmap_init_mmio_clk(dev, "bus",
> +						  base,
> +						  &config);
> +	if (IS_ERR(tmdev->regmap))
> +		return PTR_ERR(tmdev->regmap);
> +
> +	tmdev->reset = devm_reset_control_get(dev, "bus");
> +	if (IS_ERR(tmdev->reset))
> +		return PTR_ERR(tmdev->reset);
> +
> +	tmdev->bus_clk = devm_clk_get(&pdev->dev, "bus");
> +	if (IS_ERR(tmdev->bus_clk))
> +		return PTR_ERR(tmdev->bus_clk);
> +
> +	return 0;
> +}
> +
> +/*
> + * Even if the external calibration data stored in sid is not accessible,
> + * the THS hardware can still work, although the data won't be so accurate.
> + * The default value of calibration register is 0x800 for every sensor,
> + * and the calibration value is usually 0x7xx or 0x8xx, so they won't be
> + * away from the default value for a lot.
> + *
> + * So here we do not return error if the calibartion data is
> + * not available, except the probe needs deferring.
> + */
> +static int tsens_calibrate(struct tsens_device *tmdev)
> +{
> +	struct nvmem_cell *calcell;
> +	struct device *dev = tmdev->dev;
> +	u16 *caldata;
> +	size_t callen;
> +	int ft_temp;
> +	int i = 0;
> +
> +	calcell = devm_nvmem_cell_get(dev, "calib");
> +	if (IS_ERR(calcell)) {
> +		if (PTR_ERR(calcell) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +
> +		goto out;
> +	}
> +
> +	caldata = nvmem_cell_read(calcell, &callen);
> +	if (IS_ERR(caldata))
> +		goto out;
> +
> +	if (!caldata[0] || callen < 2 + 2 * tmdev->chip->sensor_num)
> +		goto out_free;
> +
> +	/*
> +	 * The calbration data on H6 is stored as temperature-value
> +	 * pair when being filled at factory test stage.
> +	 * The unit of stored FT temperature is 0.1 degreee celusis.
> +	 */

Please describe the calibration data layout more clearly.

> +	ft_temp = caldata[0] & FT_TEMP_MASK;
> +
> +	for (; i < tmdev->chip->sensor_num; i++) {
> +		int reg = (int)caldata[i + 1];
> +		int sensor_temp = tsens_reg2temp(tmdev, reg);
> +		int delta, cdata, calib_offest;
> +
> +		/*
> +		 * To calculate the calibration value:
> +		 *
> +		 * X(in Celsius) = Ts - ft_temp
> +		 * delta = X * 10000 / TEMP_TO_REG
> +		 * cdata = CALIBRATE_DEFAULT - delta
> +		 *
> +		 * cdata: calibration value
> +		 */
> +		delta = (sensor_temp - ft_temp * 100) * 10 / TEMP_TO_REG;
> +		cdata = CALIBRATE_DEFAULT - delta;
> +		if (cdata & ~TEMP_CALIB_MASK) {
> +			dev_warn(dev, "sensor%d calibration value error", i);

Please use a more descriptive error message. What error is this?

> +			continue;
> +		}
> +
> +		calib_offest = tmdev->chip->temp_calib_base + (i / 2) * 0x4;
> +		if (i % 2) {
> +			int val;
> +
> +			regmap_read(tmdev->regmap, calib_offest, &val);
> +			val = (val & TEMP_CALIB_MASK) | (cdata << 16);
> +			regmap_write(tmdev->regmap, calib_offest, val);
> +		} else
> +			regmap_write(tmdev->regmap, calib_offest, cdata);
> +	}
> +
> +out_free:
> +	kfree(caldata);
> +out:
> +	return 0;
> +}
> +
> +static int tsens_register(struct tsens_device *tmdev)
> +{
> +	struct thermal_zone_device *tzd;
> +	int i = 0;
> +
> +	for (; i < tmdev->chip->sensor_num; i++) {
> +		tmdev->sensor[i].tmdev = tmdev;
> +		tmdev->sensor[i].id = i;
> +		tmdev->sensor[i].tzd = devm_thermal_zone_of_sensor_register(
> +					tmdev->dev, i, &tmdev->sensor[i],
> +					&tsens_ops);
> +		if (IS_ERR(tmdev->sensor[i].tzd))
> +			return PTR_ERR(tzd);
> +	}
> +
> +	return 0;
> +}
> +
> +static int tsens_probe(struct platform_device *pdev)
> +{
> +	struct tsens_device *tmdev;
> +	struct device *dev = &pdev->dev;
> +	int ret;
> +
> +	tmdev = devm_kzalloc(dev, sizeof(*tmdev), GFP_KERNEL);
> +	if (!tmdev)
> +		return -ENOMEM;
> +
> +	tmdev->dev = dev;
> +	tmdev->chip = of_device_get_match_data(&pdev->dev);
> +	if (!tmdev->chip)
> +		return -EINVAL;
> +
> +	ret = tsens_init(tmdev);
> +	if (ret)
> +		return ret;
> +
> +	ret = tsens_register(tmdev);
> +	if (ret)
> +		return ret;

Why split this out of probe into separate functions?

> +	ret = tmdev->chip->enable(tmdev);
> +	if (ret)
> +		return ret;
> +
> +	platform_set_drvdata(pdev, tmdev);
> +
> +	return ret;
> +}
> +
> +static int tsens_remove(struct platform_device *pdev)
> +{
> +	struct tsens_device *tmdev = platform_get_drvdata(pdev);
> +
> +	tmdev->chip->disable(tmdev);
> +
> +	return 0;
> +}
> +
> +static int sun50i_thermal_enable(struct tsens_device *tmdev)
> +{
> +	int ret, val;
> +
> +	ret = reset_control_deassert(tmdev->reset);
> +	if (ret)
> +		return ret;
> +
> +	ret = clk_prepare_enable(tmdev->bus_clk);
> +	if (ret)
> +		goto assert_reset;
> +
> +	ret = tsens_calibrate(tmdev);
> +	if (ret)
> +		return ret;

If this fails (it may likely fail with EPROBE_DEFER) you are leaving reset
deasserted, and clock enabled.

Overall, I think, reset/clock management and nvmem reading will be common
to all the HW variants, so it doesn't make much sense splitting it out
of probe into separate functions, and makes it more error prone.

thank you and regards,
	o.

> +	/*
> +	 * clkin = 24MHz
> +	 * T acquire = clkin / (SUN50I_THS_CTRL0_T_ACQ + 1)
> +	 *           = 20us
> +	 */
> +	regmap_write(tmdev->regmap, SUN50I_THS_CTRL0,
> +		     SUN50I_THS_CTRL0_T_ACQ(479));
> +	/* average over 4 samples */
> +	regmap_write(tmdev->regmap, SUN50I_H6_THS_MFC,
> +		     SUN50I_THS_FILTER_EN |
> +		     SUN50I_THS_FILTER_TYPE(1));
> +	/* period = (SUN50I_H6_THS_PC_TEMP_PERIOD + 1) * 4096 / clkin; ~10ms */
> +	regmap_write(tmdev->regmap, SUN50I_H6_THS_PC,
> +		     SUN50I_H6_THS_PC_TEMP_PERIOD(58));
> +	/* enable sensor */
> +	val = GENMASK(tmdev->chip->sensor_num - 1, 0);
> +	regmap_write(tmdev->regmap, SUN50I_H6_THS_ENABLE, val);
> +
> +	return 0;
> +
> +assert_reset:
> +	reset_control_assert(tmdev->reset);
> +
> +	return ret;
> +}
> +
> +static int sun50i_thermal_disable(struct tsens_device *tmdev)
> +{
> +	clk_disable_unprepare(tmdev->bus_clk);
> +	reset_control_assert(tmdev->reset);
> +
> +	return 0;
> +}
> +
> +static const struct sun50i_thermal_chip sun50i_h6_ths = {
> +	.sensor_num = 2,
> +	.offset = -2794,
> +	.scale = -67,
> +	.ft_deviation = SUN50I_H6_FT_DEVIATION,
> +	.temp_calib_base = SUN50I_H6_TEMP_CALIB,
> +	.temp_data_base = SUN50I_H6_TEMP_DATA,
> +	.enable = sun50i_thermal_enable,
> +	.disable = sun50i_thermal_disable,
> +};
> +
> +static const struct of_device_id of_tsens_match[] = {
> +	{ .compatible = "allwinner,sun50i-h6-ths", .data = &sun50i_h6_ths },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, of_tsens_match);
> +
> +static struct platform_driver tsens_driver = {
> +	.probe = tsens_probe,
> +	.remove = tsens_remove,
> +	.driver = {
> +		.name = "sun50i-thermal",
> +		.of_match_table = of_tsens_match,
> +	},
> +};
> +module_platform_driver(tsens_driver);
> +
> +MODULE_DESCRIPTION("Thermal sensor driver for Allwinner SOC");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.17.0
> 
> 
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