thermal: Introduce Amazon's Annapurna Labs Thermal Driver

This is a generic thermal driver for simple MMIO sensors, of which
amazon,al-thermal is one.

This device uses a single MMIO transaction to read the temperature and
report it to the thermal subsystem.

Signed-off-by: Talel Shenhar <talel@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

4 files changed, 146 insertions, 0 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 5c38f21aee78..4d08f59bdc3e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -744,6 +744,12 @@ S:	Supported
 F:      Documentation/networking/device_drivers/amazon/ena.txt
 F:      drivers/net/ethernet/amazon/
 
+AMAZON ANNAPURNA LABS THERMAL MMIO DRIVER
+M:      Talel Shenhar <talel@amazon.com>
+S:      Maintained
+F:      Documentation/devicetree/bindings/thermal/amazon,al-thermal.txt
+F:      drivers/thermal/thermal_mmio.c
+
 AMD CRYPTOGRAPHIC COPROCESSOR (CCP) DRIVER
 M:      Tom Lendacky <thomas.lendacky@amd.com>
 M:      Gary Hook <gary.hook@amd.com>
diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index 653aa27a25a4..41f3943bfe96 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -200,6 +200,16 @@ config THERMAL_EMULATION
           because userland can easily disable the thermal policy by simply
           flooding this sysfs node with low temperature values.
 
+config THERMAL_MMIO
+        tristate "Generic Thermal MMIO driver"
+        depends on OF || COMPILE_TEST
+        help
+          This option enables the generic thermal MMIO driver that will use
+          memory-mapped reads to get the temperature.  Any HW/System that
+          allows temperature reading by a single memory-mapped reading, be it
+          register or shared memory, is a potential candidate to work with this
+          driver.
+
 config HISI_THERMAL
         tristate "Hisilicon thermal driver"
         depends on ARCH_HISI || COMPILE_TEST
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index 486d682be047..74a37c7f847a 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -29,6 +29,7 @@ thermal_sys-$(CONFIG_DEVFREQ_THERMAL) += devfreq_cooling.o
 
 # platform thermal drivers
 obj-y                           += broadcom/
+obj-$(CONFIG_THERMAL_MMIO)              += thermal_mmio.o
 obj-$(CONFIG_SPEAR_THERMAL)     += spear_thermal.o
 obj-$(CONFIG_ROCKCHIP_THERMAL)  += rockchip_thermal.o
 obj-$(CONFIG_RCAR_THERMAL)      += rcar_thermal.o
diff --git a/drivers/thermal/thermal_mmio.c b/drivers/thermal/thermal_mmio.c
new file mode 100644
index 000000000000..de3cceea23bc
--- /dev/null
+++ b/drivers/thermal/thermal_mmio.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ */
+
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/thermal.h>
+
+struct thermal_mmio {
+        void __iomem *mmio_base;
+        u32 (*read_mmio)(void __iomem *mmio_base);
+        u32 mask;
+        int factor;
+};
+
+static u32 thermal_mmio_readb(void __iomem *mmio_base)
+{
+        return readb(mmio_base);
+}
+
+static int thermal_mmio_get_temperature(void *private, int *temp)
+{
+        int t;
+        struct thermal_mmio *sensor =
+                (struct thermal_mmio *)private;
+
+        t = sensor->read_mmio(sensor->mmio_base) & sensor->mask;
+        t *= sensor->factor;
+
+        *temp = t;
+
+        return 0;
+}
+
+static struct thermal_zone_of_device_ops thermal_mmio_ops = {
+        .get_temp = thermal_mmio_get_temperature,
+};
+
+static int thermal_mmio_probe(struct platform_device *pdev)
+{
+        struct resource *resource;
+        struct thermal_mmio *sensor;
+        int (*sensor_init_func)(struct platform_device *pdev,
+                                struct thermal_mmio *sensor);
+        struct thermal_zone_device *thermal_zone;
+        int ret;
+        int temperature;
+
+        sensor = devm_kzalloc(&pdev->dev, sizeof(*sensor), GFP_KERNEL);
+        if (!sensor)
+                return -ENOMEM;
+
+        resource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        if (IS_ERR(resource)) {
+                dev_err(&pdev->dev,
+                        "fail to get platform memory resource (%ld)\n",
+                        PTR_ERR(resource));
+                return PTR_ERR(resource);
+        }
+
+        sensor->mmio_base = devm_ioremap_resource(&pdev->dev, resource);
+        if (IS_ERR(sensor->mmio_base)) {
+                dev_err(&pdev->dev, "failed to ioremap memory (%ld)\n",
+                        PTR_ERR(sensor->mmio_base));
+                return PTR_ERR(sensor->mmio_base);
+        }
+
+        sensor_init_func = device_get_match_data(&pdev->dev);
+        if (sensor_init_func) {
+                ret = sensor_init_func(pdev, sensor);
+                if (ret) {
+                        dev_err(&pdev->dev,
+                                "failed to initialize sensor (%d)\n",
+                                ret);
+                        return ret;
+                }
+        }
+
+        thermal_zone = devm_thermal_zone_of_sensor_register(&pdev->dev,
+                                                            0,
+                                                            sensor,
+                                                            &thermal_mmio_ops);
+        if (IS_ERR(thermal_zone)) {
+                dev_err(&pdev->dev,
+                        "failed to register sensor (%ld)\n",
+                        PTR_ERR(thermal_zone));
+                return PTR_ERR(thermal_zone);
+        }
+
+        thermal_mmio_get_temperature(sensor, &temperature);
+        dev_info(&pdev->dev,
+                 "thermal mmio sensor %s registered, current temperature: %d\n",
+                 pdev->name, temperature);
+
+        return 0;
+}
+
+static int al_thermal_init(struct platform_device *pdev,
+                           struct thermal_mmio *sensor)
+{
+        sensor->read_mmio = thermal_mmio_readb;
+        sensor->mask = 0xff;
+        sensor->factor = 1000;
+
+        return 0;
+}
+
+static const struct of_device_id thermal_mmio_id_table[] = {
+        { .compatible = "amazon,al-thermal", .data = al_thermal_init},
+        {}
+};
+MODULE_DEVICE_TABLE(of, thermal_mmio_id_table);
+
+static struct platform_driver thermal_mmio_driver = {
+        .probe = thermal_mmio_probe,
+        .driver = {
+                .name = "thermal-mmio",
+                .owner = THIS_MODULE,
+                .of_match_table = of_match_ptr(thermal_mmio_id_table),
+        },
+};
+
+module_platform_driver(thermal_mmio_driver);
+
+MODULE_AUTHOR("Talel Shenhar <talel@amazon.com>");
+MODULE_DESCRIPTION("Thermal MMIO Driver");
+MODULE_LICENSE("GPL v2");