hw/arm/raspi: add a skeleton implementation of the CPRMAN

The BCM2835 CPRMAN is the clock manager of the SoC. It is composed of a
main oscillator, and several sub-components (PLLs, multiplexers, ...) to
generate the BCM2835 clock tree.

This commit adds a skeleton of the CPRMAN, with a dummy register
read/write implementation. It embeds the main oscillator (xosc) from
which all the clocks will be derived.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Luc Michel <luc@lmichel.fr>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 163 insertions, 0 deletions

diff --git a/hw/misc/bcm2835_cprman.c b/hw/misc/bcm2835_cprman.c
new file mode 100644
index 0000000..57ab991
--- /dev/null
+++ b/hw/misc/bcm2835_cprman.c
@@ -0,0 +1,163 @@
+/*
+ * BCM2835 CPRMAN clock manager
+ *
+ * Copyright (c) 2020 Luc Michel <luc@lmichel.fr>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+/*
+ * This peripheral is roughly divided into 3 main parts:
+ *   - the PLLs
+ *   - the PLL channels
+ *   - the clock muxes
+ *
+ * A main oscillator (xosc) feeds all the PLLs. Each PLLs has one or more
+ * channels. Those channel are then connected to the clock muxes. Each mux has
+ * multiples sources (usually the xosc, some of the PLL channels and some "test
+ * debug" clocks). A mux is configured to select a given source through its
+ * control register. Each mux has one output clock that also goes out of the
+ * CPRMAN. This output clock usually connects to another peripheral in the SoC
+ * (so a given mux is dedicated to a peripheral).
+ *
+ * At each level (PLL, channel and mux), the clock can be altered through
+ * dividers (and multipliers in case of the PLLs), and can be disabled (in this
+ * case, the next levels see no clock).
+ *
+ * This can be sum-up as follows (this is an example and not the actual BCM2835
+ * clock tree):
+ *
+ *          /-->[PLL]-|->[PLL channel]--...            [mux]--> to peripherals
+ *          |         |->[PLL channel]  muxes takes    [mux]
+ *          |         \->[PLL channel]  inputs from    [mux]
+ *          |                           some channels  [mux]
+ * [xosc]---|-->[PLL]-|->[PLL channel]  and other srcs [mux]
+ *          |         \->[PLL channel]           ...-->[mux]
+ *          |                                          [mux]
+ *          \-->[PLL]--->[PLL channel]                 [mux]
+ *
+ * The page at https://elinux.org/The_Undocumented_Pi gives the actual clock
+ * tree configuration.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "migration/vmstate.h"
+#include "hw/qdev-properties.h"
+#include "hw/misc/bcm2835_cprman.h"
+#include "hw/misc/bcm2835_cprman_internals.h"
+#include "trace.h"
+
+/* CPRMAN "top level" model */
+
+static uint64_t cprman_read(void *opaque, hwaddr offset,
+                            unsigned size)
+{
+    BCM2835CprmanState *s = CPRMAN(opaque);
+    uint64_t r = 0;
+    size_t idx = offset / sizeof(uint32_t);
+
+    switch (idx) {
+    default:
+        r = s->regs[idx];
+    }
+
+    trace_bcm2835_cprman_read(offset, r);
+    return r;
+}
+
+static void cprman_write(void *opaque, hwaddr offset,
+                         uint64_t value, unsigned size)
+{
+    BCM2835CprmanState *s = CPRMAN(opaque);
+    size_t idx = offset / sizeof(uint32_t);
+
+    if (FIELD_EX32(value, CPRMAN, PASSWORD) != CPRMAN_PASSWORD) {
+        trace_bcm2835_cprman_write_invalid_magic(offset, value);
+        return;
+    }
+
+    value &= ~R_CPRMAN_PASSWORD_MASK;
+
+    trace_bcm2835_cprman_write(offset, value);
+    s->regs[idx] = value;
+
+}
+
+static const MemoryRegionOps cprman_ops = {
+    .read = cprman_read,
+    .write = cprman_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+    .valid = {
+        /*
+         * Although this hasn't been checked against real hardware, nor the
+         * information can be found in a datasheet, it seems reasonable because
+         * of the "PASSWORD" magic value found in every registers.
+         */
+        .min_access_size        = 4,
+        .max_access_size        = 4,
+        .unaligned              = false,
+    },
+    .impl = {
+        .max_access_size = 4,
+    },
+};
+
+static void cprman_reset(DeviceState *dev)
+{
+    BCM2835CprmanState *s = CPRMAN(dev);
+
+    memset(s->regs, 0, sizeof(s->regs));
+
+    clock_update_hz(s->xosc, s->xosc_freq);
+}
+
+static void cprman_init(Object *obj)
+{
+    BCM2835CprmanState *s = CPRMAN(obj);
+
+    s->xosc = clock_new(obj, "xosc");
+
+    memory_region_init_io(&s->iomem, obj, &cprman_ops,
+                          s, "bcm2835-cprman", 0x2000);
+    sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->iomem);
+}
+
+static const VMStateDescription cprman_vmstate = {
+    .name = TYPE_BCM2835_CPRMAN,
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32_ARRAY(regs, BCM2835CprmanState, CPRMAN_NUM_REGS),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static Property cprman_properties[] = {
+    DEFINE_PROP_UINT32("xosc-freq-hz", BCM2835CprmanState, xosc_freq, 19200000),
+    DEFINE_PROP_END_OF_LIST()
+};
+
+static void cprman_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->reset = cprman_reset;
+    dc->vmsd = &cprman_vmstate;
+    device_class_set_props(dc, cprman_properties);
+}
+
+static const TypeInfo cprman_info = {
+    .name = TYPE_BCM2835_CPRMAN,
+    .parent = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(BCM2835CprmanState),
+    .class_init = cprman_class_init,
+    .instance_init = cprman_init,
+};
+
+static void cprman_register_types(void)
+{
+    type_register_static(&cprman_info);
+}
+
+type_init(cprman_register_types);