thermal: bcm2835: add thermal driver for bcm2835 SoC

Add basic thermal driver for bcm2835 SoC.

This driver currently make sure that tsense HW block is set up
correctly.
Tested-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Eric Anholt <eric@anholt.net>
Acked-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/thermal/Kconfig

@@ -453,4 +453,12 @@ config ZX2967_THERMAL
 	  the primitive temperature sensor embedded in zx2967 SoCs.
 	  This sensor generates the real time die temperature.
 
+config BCM2835_THERMAL
+	tristate "Thermal sensors on bcm2835 SoC"
+	depends on ARCH_BCM2835 || COMPILE_TEST
+	depends on HAS_IOMEM
+	depends on THERMAL_OF
+	help
+	  Support for thermal sensors on Broadcom bcm2835 SoCs.
+
 endif

drivers/thermal/Makefile

@@ -58,3 +58,4 @@ obj-$(CONFIG_HISI_THERMAL)     += hisi_thermal.o
 obj-$(CONFIG_MTK_THERMAL)	+= mtk_thermal.o
 obj-$(CONFIG_GENERIC_ADC_THERMAL)	+= thermal-generic-adc.o
 obj-$(CONFIG_ZX2967_THERMAL)	+= zx2967_thermal.o
+obj-$(CONFIG_BCM2835_THERMAL)	+= bcm2835_thermal.o

drivers/thermal/bcm2835_thermal.c

+/*
+ * Driver for Broadcom BCM2835 SoC temperature sensor
+ *
+ * Copyright (C) 2016 Martin Sperl
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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/clk.h>
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/thermal.h>
+
+#define BCM2835_TS_TSENSCTL			0x00
+#define BCM2835_TS_TSENSSTAT			0x04
+
+#define BCM2835_TS_TSENSCTL_PRWDW		BIT(0)
+#define BCM2835_TS_TSENSCTL_RSTB		BIT(1)
+
+/*
+ * bandgap reference voltage in 6 mV increments
+ * 000b = 1178 mV, 001b = 1184 mV, ... 111b = 1220 mV
+ */
+#define BCM2835_TS_TSENSCTL_CTRL_BITS		3
+#define BCM2835_TS_TSENSCTL_CTRL_SHIFT		2
+#define BCM2835_TS_TSENSCTL_CTRL_MASK		    \
+	GENMASK(BCM2835_TS_TSENSCTL_CTRL_BITS +     \
+		BCM2835_TS_TSENSCTL_CTRL_SHIFT - 1, \
+		BCM2835_TS_TSENSCTL_CTRL_SHIFT)
+#define BCM2835_TS_TSENSCTL_CTRL_DEFAULT	1
+#define BCM2835_TS_TSENSCTL_EN_INT		BIT(5)
+#define BCM2835_TS_TSENSCTL_DIRECT		BIT(6)
+#define BCM2835_TS_TSENSCTL_CLR_INT		BIT(7)
+#define BCM2835_TS_TSENSCTL_THOLD_SHIFT		8
+#define BCM2835_TS_TSENSCTL_THOLD_BITS		10
+#define BCM2835_TS_TSENSCTL_THOLD_MASK		     \
+	GENMASK(BCM2835_TS_TSENSCTL_THOLD_BITS +     \
+		BCM2835_TS_TSENSCTL_THOLD_SHIFT - 1, \
+		BCM2835_TS_TSENSCTL_THOLD_SHIFT)
+/*
+ * time how long the block to be asserted in reset
+ * which based on a clock counter (TSENS clock assumed)
+ */
+#define BCM2835_TS_TSENSCTL_RSTDELAY_SHIFT	18
+#define BCM2835_TS_TSENSCTL_RSTDELAY_BITS	8
+#define BCM2835_TS_TSENSCTL_REGULEN		BIT(26)
+
+#define BCM2835_TS_TSENSSTAT_DATA_BITS		10
+#define BCM2835_TS_TSENSSTAT_DATA_SHIFT		0
+#define BCM2835_TS_TSENSSTAT_DATA_MASK		     \
+	GENMASK(BCM2835_TS_TSENSSTAT_DATA_BITS +     \
+		BCM2835_TS_TSENSSTAT_DATA_SHIFT - 1, \
+		BCM2835_TS_TSENSSTAT_DATA_SHIFT)
+#define BCM2835_TS_TSENSSTAT_VALID		BIT(10)
+#define BCM2835_TS_TSENSSTAT_INTERRUPT		BIT(11)
+
+struct bcm2835_thermal_data {
+	struct thermal_zone_device *tz;
+	void __iomem *regs;
+	struct clk *clk;
+	struct dentry *debugfsdir;
+};
+
+static int bcm2835_thermal_adc2temp(u32 adc, int offset, int slope)
+{
+	return offset + slope * adc;
+}
+
+static int bcm2835_thermal_temp2adc(int temp, int offset, int slope)
+{
+	temp -= offset;
+	temp /= slope;
+
+	if (temp < 0)
+		temp = 0;
+	if (temp >= BIT(BCM2835_TS_TSENSSTAT_DATA_BITS))
+		temp = BIT(BCM2835_TS_TSENSSTAT_DATA_BITS) - 1;
+
+	return temp;
+}
+
+static int bcm2835_thermal_get_temp(void *d, int *temp)
+{
+	struct bcm2835_thermal_data *data = d;
+	u32 val = readl(data->regs + BCM2835_TS_TSENSSTAT);
+
+	if (!(val & BCM2835_TS_TSENSSTAT_VALID))
+		return -EIO;
+
+	val &= BCM2835_TS_TSENSSTAT_DATA_MASK;
+
+	*temp = bcm2835_thermal_adc2temp(
+		val,
+		thermal_zone_get_offset(data->tz),
+		thermal_zone_get_slope(data->tz));
+
+	return 0;
+}
+
+static const struct debugfs_reg32 bcm2835_thermal_regs[] = {
+	{
+		.name = "ctl",
+		.offset = 0
+	},
+	{
+		.name = "stat",
+		.offset = 4
+	}
+};
+
+static void bcm2835_thermal_debugfs(struct platform_device *pdev)
+{
+	struct thermal_zone_device *tz = platform_get_drvdata(pdev);
+	struct bcm2835_thermal_data *data = tz->devdata;
+	struct debugfs_regset32 *regset;
+
+	data->debugfsdir = debugfs_create_dir("bcm2835_thermal", NULL);
+	if (!data->debugfsdir)
+		return;
+
+	regset = devm_kzalloc(&pdev->dev, sizeof(*regset), GFP_KERNEL);
+	if (!regset)
+		return;
+
+	regset->regs = bcm2835_thermal_regs;
+	regset->nregs = ARRAY_SIZE(bcm2835_thermal_regs);
+	regset->base = data->regs;
+
+	debugfs_create_regset32("regset", 0444, data->debugfsdir, regset);
+}
+
+static struct thermal_zone_of_device_ops bcm2835_thermal_ops = {
+	.get_temp = bcm2835_thermal_get_temp,
+};
+
+/*
+ * Note: as per Raspberry Foundation FAQ
+ * (https://www.raspberrypi.org/help/faqs/#performanceOperatingTemperature)
+ * the recommended temperature range for the SoC -40C to +85C
+ * so the trip limit is set to 80C.
+ * this applies to all the BCM283X SoC
+ */
+
+static const struct of_device_id bcm2835_thermal_of_match_table[] = {
+	{
+		.compatible = "brcm,bcm2835-thermal",
+	},
+	{
+		.compatible = "brcm,bcm2836-thermal",
+	},
+	{
+		.compatible = "brcm,bcm2837-thermal",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, bcm2835_thermal_of_match_table);
+
+static int bcm2835_thermal_probe(struct platform_device *pdev)
+{
+	const struct of_device_id *match;
+	struct thermal_zone_device *tz;
+	struct bcm2835_thermal_data *data;
+	struct resource *res;
+	int err = 0;
+	u32 val;
+	unsigned long rate;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	match = of_match_device(bcm2835_thermal_of_match_table,
+				&pdev->dev);
+	if (!match)
+		return -EINVAL;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	data->regs = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(data->regs)) {
+		err = PTR_ERR(data->regs);
+		dev_err(&pdev->dev, "Could not get registers: %d\n", err);
+		return err;
+	}
+
+	data->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(data->clk)) {
+		err = PTR_ERR(data->clk);
+		if (err != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "Could not get clk: %d\n", err);
+		return err;
+	}
+
+	err = clk_prepare_enable(data->clk);
+	if (err)
+		return err;
+
+	rate = clk_get_rate(data->clk);
+	if ((rate < 1920000) || (rate > 5000000))
+		dev_warn(&pdev->dev,
+			 "Clock %pCn running at %pCr Hz is outside of the recommended range: 1.92 to 5MHz\n",
+			 data->clk, data->clk);
+
+	/* register of thermal sensor and get info from DT */
+	tz = thermal_zone_of_sensor_register(&pdev->dev, 0, data,
+					     &bcm2835_thermal_ops);
+	if (IS_ERR(tz)) {
+		err = PTR_ERR(tz);
+		dev_err(&pdev->dev,
+			"Failed to register the thermal device: %d\n",
+			err);
+		goto err_clk;
+	}
+
+	/*
+	 * right now the FW does set up the HW-block, so we are not
+	 * touching the configuration registers.
+	 * But if the HW is not enabled, then set it up
+	 * using "sane" values used by the firmware right now.
+	 */
+	val = readl(data->regs + BCM2835_TS_TSENSCTL);
+	if (!(val & BCM2835_TS_TSENSCTL_RSTB)) {
+		int trip_temp, offset, slope;
+
+		slope = thermal_zone_get_slope(tz);
+		offset = thermal_zone_get_offset(tz);
+		/*
+		 * For now we deal only with critical, otherwise
+		 * would need to iterate
+		 */
+		err = tz->ops->get_trip_temp(tz, 0, &trip_temp);
+		if (err < 0) {
+			err = PTR_ERR(tz);
+			dev_err(&pdev->dev,
+				"Not able to read trip_temp: %d\n",
+				err);
+			goto err_tz;
+		}
+
+		/* set bandgap reference voltage and enable voltage regulator */
+		val = (BCM2835_TS_TSENSCTL_CTRL_DEFAULT <<
+		       BCM2835_TS_TSENSCTL_CTRL_SHIFT) |
+		      BCM2835_TS_TSENSCTL_REGULEN;
+
+		/* use the recommended reset duration */
+		val |= (0xFE << BCM2835_TS_TSENSCTL_RSTDELAY_SHIFT);
+
+		/*  trip_adc value from info */
+		val |= bcm2835_thermal_temp2adc(trip_temp,
+						offset,
+						slope)
+			<< BCM2835_TS_TSENSCTL_THOLD_SHIFT;
+
+		/* write the value back to the register as 2 steps */
+		writel(val, data->regs + BCM2835_TS_TSENSCTL);
+		val |= BCM2835_TS_TSENSCTL_RSTB;
+		writel(val, data->regs + BCM2835_TS_TSENSCTL);
+	}
+
+	data->tz = tz;
+
+	platform_set_drvdata(pdev, tz);
+
+	bcm2835_thermal_debugfs(pdev);
+
+	return 0;
+err_tz:
+	thermal_zone_of_sensor_unregister(&pdev->dev, tz);
+err_clk:
+	clk_disable_unprepare(data->clk);
+
+	return err;
+}
+
+static int bcm2835_thermal_remove(struct platform_device *pdev)
+{
+	struct thermal_zone_device *tz = platform_get_drvdata(pdev);
+	struct bcm2835_thermal_data *data = tz->devdata;
+
+	debugfs_remove_recursive(data->debugfsdir);
+	thermal_zone_of_sensor_unregister(&pdev->dev, tz);
+	clk_disable_unprepare(data->clk);
+
+	return 0;
+}
+
+static struct platform_driver bcm2835_thermal_driver = {
+	.probe = bcm2835_thermal_probe,
+	.remove = bcm2835_thermal_remove,
+	.driver = {
+		.name = "bcm2835_thermal",
+		.of_match_table = bcm2835_thermal_of_match_table,
+	},
+};
+module_platform_driver(bcm2835_thermal_driver);
+
+MODULE_AUTHOR("Martin Sperl");
+MODULE_DESCRIPTION("Thermal driver for bcm2835 chip");
+MODULE_LICENSE("GPL");