hw/misc/bcm2835_thermal: Add a dummy BCM2835 thermal sensor

We will soon implement the SYS_timer. This timer is used by Linux
in the thermal subsystem, so once available, the subsystem will be
enabled and poll the temperature sensors. We need to provide the
minimum required to keep Linux booting.

Add a dummy thermal sensor returning ~25°C based on:
https://github.com/raspberrypi/linux/blob/rpi-5.3.y/drivers/thermal/broadcom/bcm2835_thermal.c

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20191019234715.25750-2-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 136 insertions, 0 deletions

diff --git a/hw/misc/Makefile.objs b/hw/misc/Makefile.objs
index a150680966..c89f3816a5 100644
--- a/hw/misc/Makefile.objs
+++ b/hw/misc/Makefile.objs
@@ -53,6 +53,7 @@ common-obj-$(CONFIG_OMAP) += omap_tap.o
 common-obj-$(CONFIG_RASPI) += bcm2835_mbox.o
 common-obj-$(CONFIG_RASPI) += bcm2835_property.o
 common-obj-$(CONFIG_RASPI) += bcm2835_rng.o
+common-obj-$(CONFIG_RASPI) += bcm2835_thermal.o
 common-obj-$(CONFIG_SLAVIO) += slavio_misc.o
 common-obj-$(CONFIG_ZYNQ) += zynq_slcr.o
 common-obj-$(CONFIG_ZYNQ) += zynq-xadc.o
diff --git a/hw/misc/bcm2835_thermal.c b/hw/misc/bcm2835_thermal.c
new file mode 100644
index 0000000000..c6f3b1ad60
--- /dev/null
+++ b/hw/misc/bcm2835_thermal.c
@@ -0,0 +1,135 @@
+/*
+ * BCM2835 dummy thermal sensor
+ *
+ * Copyright (C) 2019 Philippe Mathieu-Daudé <f4bug@amsat.org>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "qapi/error.h"
+#include "hw/misc/bcm2835_thermal.h"
+#include "hw/registerfields.h"
+#include "migration/vmstate.h"
+
+REG32(CTL, 0)
+FIELD(CTL, POWER_DOWN, 0, 1)
+FIELD(CTL, RESET, 1, 1)
+FIELD(CTL, BANDGAP_CTRL, 2, 3)
+FIELD(CTL, INTERRUPT_ENABLE, 5, 1)
+FIELD(CTL, DIRECT, 6, 1)
+FIELD(CTL, INTERRUPT_CLEAR, 7, 1)
+FIELD(CTL, HOLD, 8, 10)
+FIELD(CTL, RESET_DELAY, 18, 8)
+FIELD(CTL, REGULATOR_ENABLE, 26, 1)
+
+REG32(STAT, 4)
+FIELD(STAT, DATA, 0, 10)
+FIELD(STAT, VALID, 10, 1)
+FIELD(STAT, INTERRUPT, 11, 1)
+
+#define THERMAL_OFFSET_C 412
+#define THERMAL_COEFF  (-0.538f)
+
+static uint16_t bcm2835_thermal_temp2adc(int temp_C)
+{
+    return (temp_C - THERMAL_OFFSET_C) / THERMAL_COEFF;
+}
+
+static uint64_t bcm2835_thermal_read(void *opaque, hwaddr addr, unsigned size)
+{
+    Bcm2835ThermalState *s = BCM2835_THERMAL(opaque);
+    uint32_t val = 0;
+
+    switch (addr) {
+    case A_CTL:
+        val = s->ctl;
+        break;
+    case A_STAT:
+        /* Temperature is constantly 25°C. */
+        val = FIELD_DP32(bcm2835_thermal_temp2adc(25), STAT, VALID, true);
+        break;
+    default:
+        /* MemoryRegionOps are aligned, so this can not happen. */
+        g_assert_not_reached();
+    }
+    return val;
+}
+
+static void bcm2835_thermal_write(void *opaque, hwaddr addr,
+                                  uint64_t value, unsigned size)
+{
+    Bcm2835ThermalState *s = BCM2835_THERMAL(opaque);
+
+    switch (addr) {
+    case A_CTL:
+        s->ctl = value;
+        break;
+    case A_STAT:
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: write 0x%" PRIx64
+                                       " to 0x%" HWADDR_PRIx "\n",
+                       __func__, value, addr);
+        break;
+    default:
+        /* MemoryRegionOps are aligned, so this can not happen. */
+        g_assert_not_reached();
+    }
+}
+
+static const MemoryRegionOps bcm2835_thermal_ops = {
+    .read = bcm2835_thermal_read,
+    .write = bcm2835_thermal_write,
+    .impl.max_access_size = 4,
+    .valid.min_access_size = 4,
+    .endianness = DEVICE_NATIVE_ENDIAN,
+};
+
+static void bcm2835_thermal_reset(DeviceState *dev)
+{
+    Bcm2835ThermalState *s = BCM2835_THERMAL(dev);
+
+    s->ctl = 0;
+}
+
+static void bcm2835_thermal_realize(DeviceState *dev, Error **errp)
+{
+    Bcm2835ThermalState *s = BCM2835_THERMAL(dev);
+
+    memory_region_init_io(&s->iomem, OBJECT(s), &bcm2835_thermal_ops,
+                          s, TYPE_BCM2835_THERMAL, 8);
+    sysbus_init_mmio(SYS_BUS_DEVICE(s), &s->iomem);
+}
+
+static const VMStateDescription bcm2835_thermal_vmstate = {
+    .name = "bcm2835_thermal",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32(ctl, Bcm2835ThermalState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static void bcm2835_thermal_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->realize = bcm2835_thermal_realize;
+    dc->reset = bcm2835_thermal_reset;
+    dc->vmsd = &bcm2835_thermal_vmstate;
+}
+
+static const TypeInfo bcm2835_thermal_info = {
+    .name = TYPE_BCM2835_THERMAL,
+    .parent = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(Bcm2835ThermalState),
+    .class_init = bcm2835_thermal_class_init,
+};
+
+static void bcm2835_thermal_register_types(void)
+{
+    type_register_static(&bcm2835_thermal_info);
+}
+
+type_init(bcm2835_thermal_register_types)