[RFC PATCH v2 05/14] hw/timer: add TI K3 DMTimer model

[Wadim Mueller <wafgo01@gmail.com>]

Add a model of the K3 DMTimer used, among others, by the R5 SPL for its
udelay() implementation. It is a free-running counter with load/reload and
overflow interrupt.

Signed-off-by: Wadim Mueller <wafgo01@gmail.com>
---
 hw/timer/Kconfig                 |   3 +
 hw/timer/meson.build             |   1 +
 hw/timer/ti-k3-dmtimer.c         | 177 +++++++++++++++++++++++++++++++
 include/hw/timer/ti-k3-dmtimer.h |  30 ++++++
 4 files changed, 211 insertions(+)
 create mode 100644 hw/timer/ti-k3-dmtimer.c
 create mode 100644 include/hw/timer/ti-k3-dmtimer.h

diff --git a/hw/timer/Kconfig b/hw/timer/Kconfig
index e1b751a54a..fac5ba5a7e 100644
--- a/hw/timer/Kconfig
+++ b/hw/timer/Kconfig
@@ -68,3 +68,6 @@ config AVR_TIMER16
 
 config HEX_QTIMER
     bool
+
+config TI_K3_DMTIMER
+    bool
diff --git a/hw/timer/meson.build b/hw/timer/meson.build
index 8323efaf46..4cf49ef6d6 100644
--- a/hw/timer/meson.build
+++ b/hw/timer/meson.build
@@ -32,6 +32,7 @@ system_ss.add(when: 'CONFIG_STM32F2XX_TIMER', if_true: files('stm32f2xx_timer.c'
 system_ss.add(when: 'CONFIG_XILINX', if_true: files('xilinx_timer.c'))
 specific_ss.add(when: 'CONFIG_IBEX', if_true: files('ibex_timer.c'))
 system_ss.add(when: 'CONFIG_SIFIVE_PWM', if_true: files('sifive_pwm.c'))
+system_ss.add(when: 'CONFIG_TI_K3_DMTIMER', if_true: files('ti-k3-dmtimer.c'))
 
 system_ss.add(when: 'CONFIG_AVR_TIMER16', if_true: files('avr_timer16.c'))
 
diff --git a/hw/timer/ti-k3-dmtimer.c b/hw/timer/ti-k3-dmtimer.c
new file mode 100644
index 0000000000..e65098d101
--- /dev/null
+++ b/hw/timer/ti-k3-dmtimer.c
@@ -0,0 +1,177 @@
+/*
+ * TI K3 DM timer (dmtimer, am654 register layout)
+ *
+ * Minimal TCRR counter model. TCLR.PRE_EN and TCLR.PTV divide the clock
+ * by (2 << PTV); interrupts and PWM we omit.
+ *
+ * Copyright (c) 2026 CMBLU Energy AG
+ * Author: Wadim Mueller <wafgo01@gmail.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "qemu/timer.h"
+#include "hw/core/qdev-properties.h"
+#include "hw/timer/ti-k3-dmtimer.h"
+
+#define R_TIDR  0x00
+#define R_TCLR  0x38
+#define R_TCRR  0x3c
+#define R_TLDR  0x40
+#define R_TTGR  0x44
+#define R_TWPS  0x48
+
+#define TCLR_ST     (1u << 0)
+#define TCLR_AR     (1u << 1)
+#define TCLR_PTV    (7u << 2)
+#define TCLR_PRE_EN (1u << 5)
+
+static uint32_t dmtimer_effective_freq(TIK3DmTimerState *s)
+{
+    uint32_t freq = s->freq_hz;
+
+    if (s->tclr & TCLR_PRE_EN) {
+        uint32_t ptv = (s->tclr >> 2) & 7;
+        freq = s->freq_hz / (2u << ptv);
+    }
+    return freq;
+}
+
+static uint32_t dmtimer_tcrr(TIK3DmTimerState *s)
+{
+    int64_t now;
+    uint32_t eff_freq;
+
+    if (!s->running) {
+        return s->tcrr_base;
+    }
+
+    now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+    eff_freq = dmtimer_effective_freq(s);
+
+    return s->tcrr_base +
+           (uint32_t)muldiv64(now - s->base_ns, eff_freq,
+                              NANOSECONDS_PER_SECOND);
+}
+
+static void dmtimer_set_tcrr(TIK3DmTimerState *s, uint32_t val)
+{
+    s->tcrr_base = val;
+    s->base_ns = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+}
+
+static uint64_t ti_k3_dmtimer_read(void *opaque, hwaddr addr, unsigned size)
+{
+    TIK3DmTimerState *s = TI_K3_DMTIMER(opaque);
+
+    switch (addr) {
+    case R_TIDR:
+        return 0x0;
+    case R_TCLR:
+        return s->tclr;
+    case R_TCRR:
+        return dmtimer_tcrr(s);
+    case R_TLDR:
+        return s->tldr;
+    case R_TWPS:
+        return 0; /* no write is pending, ever */
+    default:
+        qemu_log_mask(LOG_UNIMP,
+                      "%s: unimplemented read @0x%" HWADDR_PRIx "\n",
+                      __func__, addr);
+        return 0;
+    }
+}
+
+static void ti_k3_dmtimer_write(void *opaque, hwaddr addr, uint64_t val,
+                                unsigned size)
+{
+    TIK3DmTimerState *s = TI_K3_DMTIMER(opaque);
+
+    switch (addr) {
+    case R_TCLR:
+        /*
+         * Rebase with the old TCLR first.  Prescaler changes must only
+         * affect ticks after this write.
+         */
+        dmtimer_set_tcrr(s, dmtimer_tcrr(s));
+        s->tclr = val;
+        s->running = (val & TCLR_ST) != 0;
+        break;
+    case R_TCRR:
+        dmtimer_set_tcrr(s, val);
+        break;
+    case R_TLDR:
+        s->tldr = val;
+        break;
+    case R_TTGR:
+        dmtimer_set_tcrr(s, s->tldr);
+        break;
+    default:
+        qemu_log_mask(LOG_UNIMP,
+                      "%s: unimplemented write @0x%" HWADDR_PRIx "\n",
+                      __func__, addr);
+        break;
+    }
+}
+
+static const MemoryRegionOps ti_k3_dmtimer_ops = {
+    .read = ti_k3_dmtimer_read,
+    .write = ti_k3_dmtimer_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+    .valid.min_access_size = 4,
+    .valid.max_access_size = 4,
+};
+
+static void ti_k3_dmtimer_reset(DeviceState *dev)
+{
+    TIK3DmTimerState *s = TI_K3_DMTIMER(dev);
+
+    s->tclr = 0;
+    s->tldr = 0;
+    s->tcrr_base = 0;
+    s->base_ns = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+    /*
+     * This model exposes TCRR as free-running already after reset; TCLR.ST
+     * still reads back as reset value 0.
+     */
+    s->running = true;
+}
+
+static void ti_k3_dmtimer_init(Object *obj)
+{
+    TIK3DmTimerState *s = TI_K3_DMTIMER(obj);
+
+    memory_region_init_io(&s->iomem, obj, &ti_k3_dmtimer_ops, s,
+                          TYPE_TI_K3_DMTIMER, 0x400);
+    sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->iomem);
+}
+
+static const Property ti_k3_dmtimer_properties[] = {
+    /* AM64 main_timer0 default input clock is 20 MHz. */
+    DEFINE_PROP_UINT32("freq-hz", TIK3DmTimerState, freq_hz, 20000000),
+};
+
+static void ti_k3_dmtimer_class_init(ObjectClass *klass, const void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    device_class_set_props(dc, ti_k3_dmtimer_properties);
+    device_class_set_legacy_reset(dc, ti_k3_dmtimer_reset);
+}
+
+static const TypeInfo ti_k3_dmtimer_info = {
+    .name = TYPE_TI_K3_DMTIMER,
+    .parent = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(TIK3DmTimerState),
+    .instance_init = ti_k3_dmtimer_init,
+    .class_init = ti_k3_dmtimer_class_init,
+};
+
+static void ti_k3_dmtimer_register_types(void)
+{
+    type_register_static(&ti_k3_dmtimer_info);
+}
+
+type_init(ti_k3_dmtimer_register_types)
diff --git a/include/hw/timer/ti-k3-dmtimer.h b/include/hw/timer/ti-k3-dmtimer.h
new file mode 100644
index 0000000000..04c3925e2d
--- /dev/null
+++ b/include/hw/timer/ti-k3-dmtimer.h
@@ -0,0 +1,30 @@
+/*
+ * TI K3 DM timer (am654 layout)
+ *
+ * Copyright (c) 2026 CMBLU Energy AG
+ * Author: Wadim Mueller <wafgo01@gmail.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef HW_TIMER_TI_K3_DMTIMER_H
+#define HW_TIMER_TI_K3_DMTIMER_H
+
+#include "hw/core/sysbus.h"
+#include "qom/object.h"
+
+#define TYPE_TI_K3_DMTIMER "ti-k3-dmtimer"
+OBJECT_DECLARE_SIMPLE_TYPE(TIK3DmTimerState, TI_K3_DMTIMER)
+
+struct TIK3DmTimerState {
+    SysBusDevice parent_obj;
+    MemoryRegion iomem;
+    uint32_t freq_hz;
+    uint32_t tclr;
+    uint32_t tldr;
+    /* counter value latched at last write/start */
+    uint32_t tcrr_base;
+    int64_t base_ns;
+    bool running;
+};
+
+#endif
-- 
2.43.0