kern/amd64: Add initial HPET driver

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 161 insertions, 0 deletions

diff --git a/src/sys/arch/amd64/io/hpet.c b/src/sys/arch/amd64/io/hpet.c
new file mode 100644
index 0000000..7b7ea35
--- /dev/null
+++ b/src/sys/arch/amd64/io/hpet.c
@@ -0,0 +1,161 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the project nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * Description: IA-PC HPET timer driver
+ * Author: Ian Marco Moffett
+ */
+
+#include <sys/types.h>
+#include <sys/errno.h>
+#include <sys/param.h>
+#include <sys/syslog.h>
+#include <os/mmio.h>
+#include <acpi/acpi.h>
+#include <acpi/tables.h>
+#include <machine/hpet.h>
+
+#define HPET_REG_CAPS               0x00
+#define HPET_GENERAL_CONFIG         0x10
+#define HPET_REG_MAIN_COUNTER       0xF0
+
+#define CAP_REV_ID(caps)            (caps & 0xFF)
+#define CAP_NUM_TIM(caps)           (caps >> 8) & 0x1F
+#define CAP_CLK_PERIOD(caps)        (caps >> 32)
+
+static void *hpet_base = NULL;
+
+/*
+ * Read from HPET register space.
+ *
+ * @reg: Register to read from.
+ */
+static inline uint64_t
+hpet_read(uint32_t reg)
+{
+    void *addr;
+
+    addr = PTR_OFFSET(hpet_base, reg);
+    return mmio_read64(addr);
+}
+
+/*
+ * Write to HPET register space.
+ *
+ * @reg: Register to write to.
+ * @val: Value to write.
+ */
+static inline void
+hpet_write(uint32_t reg, uint64_t val)
+{
+    void *addr;
+
+    addr = PTR_OFFSET(hpet_base, reg);
+    mmio_write64(addr, val);
+}
+
+/*
+ * Sleep for 'n' amount of 'units'
+ *
+ * @n: Number of 'units' to sleep
+ * @units: Units per 'n'
+ *
+ * Returns zero on success, otherwise a less than zero
+ * value.
+ */
+static int
+hpet_sleep(uint64_t n, uint64_t units)
+{
+    uint64_t caps;
+    uint32_t period;
+    uint64_t counter_val;
+    volatile size_t ticks;
+
+    caps = hpet_read(HPET_REG_CAPS);
+    period = CAP_CLK_PERIOD(caps);
+    counter_val = hpet_read(HPET_REG_MAIN_COUNTER);
+
+    ticks = counter_val + (n * (units / period));
+
+    while (hpet_read(HPET_REG_MAIN_COUNTER) < ticks) {
+        __ASMV("rep; nop");
+    }
+
+    return 0;
+}
+
+static int
+hpet_msleep(size_t ms)
+{
+    return hpet_sleep(ms, 1000000000000);
+}
+
+/*
+ * Initialize the HPET
+ */
+int
+hpet_init(void)
+{
+    struct acpi_gas *gas;
+    struct acpi_hpet *hpet;
+    uint64_t caps;
+
+    hpet = acpi_query("HPET");
+    if (hpet == NULL) {
+        return -ENODEV;
+    }
+
+    gas = &hpet->gas;
+    hpet_base = (void *)gas->address;
+
+    caps = hpet_read(HPET_REG_CAPS);
+    if (CAP_REV_ID(caps) == 0) {
+        printf("hpet_init: bad revision HPET ID\n");
+        return -1;
+    }
+
+    /*
+     * The spec states this counter clk period must
+     * be <= 0x05F5E100. So we'll consider it as bogus
+     * if it exceeds this value
+     */
+    if (CAP_CLK_PERIOD(caps) > 0x05F5E100) {
+        printf("hpet_init: bad COUNTER_CLK_PERIOD\n");
+        return -1;
+    }
+
+    /*
+     * Clear the counter and enable the HPET via
+     * the ENABLE_CNF bit in general_config
+     */
+    hpet_write(HPET_REG_MAIN_COUNTER, 0);
+    hpet_write(HPET_GENERAL_CONFIG, 1);
+    printf("hpet: HPET initialized and enabled\n");
+    return 0;
+}