Add HPET timer for small accurate delays

TESTED: This works in qemu correctly
TESTED: This works on an AMD board with ACPI v2.0 correctly

Message-ID: <20240207050158.1640853-3-damien@zamaudio.com>

5 files changed, 150 insertions, 8 deletions

diff --git a/i386/i386/apic.c b/i386/i386/apic.c
index feb49c85..0b5be50f 100644
--- a/i386/i386/apic.c
+++ b/i386/i386/apic.c
@@ -26,6 +26,10 @@
 #include <kern/printf.h>
 #include <kern/kalloc.h>
 
+/*
+ * Period of HPET timer in nanoseconds
+ */
+uint32_t hpet_period_nsec;
 
 /*
  * This dummy structure is needed so that CPU_NUMBER can be called
@@ -362,3 +366,88 @@ lapic_eoi(void)
 {
     lapic->eoi.r = 0;
 }
+
+#define HPET32(x) *((volatile uint32_t *)((uint8_t *)hpet_addr + x))
+#define HPET_CAP_PERIOD			0x04
+#define HPET_CFG			0x10
+# define HPET_CFG_ENABLE		(1 << 0)
+# define HPET_LEGACY_ROUTE		(1 << 1)
+#define HPET_COUNTER			0xf0
+#define HPET_T0_CFG			0x100
+# define HPET_T0_32BIT_MODE		(1 << 8)
+# define HPET_T0_VAL_SET		(1 << 6)
+# define HPET_T0_TYPE_PERIODIC		(1 << 3)
+# define HPET_T0_INT_ENABLE		(1 << 2)
+#define HPET_T0_COMPARATOR		0x108
+
+#define FSEC_PER_NSEC			1000000
+#define NSEC_PER_USEC			1000
+
+/* This function sets up the HPET timer to be in
+ * 32 bit periodic mode and not generating any interrupts.
+ * The timer counts upwards and when it reaches 0xffffffff it
+ * wraps to zero.  The timer ticks at a constant rate in nanoseconds which
+ * is stored in hpet_period_nsec variable.
+ */
+void
+hpet_init(void)
+{
+    uint32_t period;
+    uint32_t val;
+
+    assert(hpet_addr != 0);
+
+    /* Find out how often the HPET ticks in nanoseconds */
+    period = HPET32(HPET_CAP_PERIOD);
+    hpet_period_nsec = period / FSEC_PER_NSEC;
+    printf("HPET ticks every %d nanoseconds\n", hpet_period_nsec);
+
+    /* Disable HPET and legacy interrupt routing mode */
+    val = HPET32(HPET_CFG);
+    val = val & ~(HPET_LEGACY_ROUTE | HPET_CFG_ENABLE);
+    HPET32(HPET_CFG) = val;
+
+    /* Clear the counter */
+    HPET32(HPET_COUNTER) = 0;
+
+    /* Set up 32 bit periodic timer with no interrupts */
+    val = HPET32(HPET_T0_CFG);
+    val = (val & ~HPET_T0_INT_ENABLE) | HPET_T0_32BIT_MODE | HPET_T0_TYPE_PERIODIC | HPET_T0_VAL_SET;
+    HPET32(HPET_T0_CFG) = val;
+
+    /* Set comparator to max */
+    HPET32(HPET_T0_COMPARATOR) = 0xffffffff;
+
+    /* Enable the HPET */
+    HPET32(HPET_CFG) |= HPET_CFG_ENABLE;
+
+    printf("HPET enabled\n");
+}
+
+void
+hpet_udelay(uint32_t us)
+{
+    uint32_t start, now;
+    uint32_t max_delay_us = 0xffffffff / NSEC_PER_USEC;
+
+    if (us > max_delay_us) {
+        printf("HPET ERROR: Delay too long, %d usec, truncating to %d usec\n",
+               us, max_delay_us);
+        us = max_delay_us;
+    }
+
+    /* Convert us to HPET ticks */
+    us = (us * NSEC_PER_USEC) / hpet_period_nsec;
+
+    start = HPET32(HPET_COUNTER);
+    do {
+        now = HPET32(HPET_COUNTER);
+    } while (now - start < us);
+}
+
+void
+hpet_mdelay(uint32_t ms)
+{
+    hpet_udelay(ms * 1000);
+}
+
diff --git a/i386/i386/apic.h b/i386/i386/apic.h
index 29387d9d..9eef0d8b 100644
--- a/i386/i386/apic.h
+++ b/i386/i386/apic.h
@@ -252,10 +252,15 @@ void calibrate_lapic_timer(void);
 void ioapic_toggle(int pin, int mask);
 void ioapic_configure(void);
 
+void hpet_init(void);
+void hpet_udelay(uint32_t us);
+void hpet_mdelay(uint32_t ms);
+
 extern int timer_pin;
 extern void intnull(int unit);
 extern volatile ApicLocalUnit* lapic;
 extern int cpu_id_lut[];
+extern uint32_t *hpet_addr;
 
 #endif
 
diff --git a/i386/i386at/acpi_parse_apic.c b/i386/i386at/acpi_parse_apic.c
index dcd5da89..1cfc1791 100644
--- a/i386/i386at/acpi_parse_apic.c
+++ b/i386/i386at/acpi_parse_apic.c
@@ -34,6 +34,7 @@
 
 static struct acpi_apic *apic_madt = NULL;
 unsigned lapic_addr;
+uint32_t *hpet_addr;
 
 /*
  * acpi_print_info: shows by screen the ACPI's rsdp and rsdt virtual address
@@ -292,28 +293,37 @@ acpi_get_xsdt(phys_addr_t rsdp_phys, int* acpi_xsdt_n)
  * and the number of entries of RSDT table.
  *
  * Returns a reference to APIC/MADT table if success, NULL if failure.
+ * Also sets hpet_addr to base address of HPET.
  */
 static struct acpi_apic*
 acpi_get_apic(struct acpi_rsdt *rsdt, int acpi_rsdt_n)
 {
     struct acpi_dhdr *descr_header;
+    struct acpi_apic *madt = NULL;
     int check_signature;
+    uint64_t map_addr;
 
     /* Search APIC entries in rsdt table. */
     for (int i = 0; i < acpi_rsdt_n; i++) {
         descr_header = (struct acpi_dhdr*) kmem_map_aligned_table(rsdt->entry[i], sizeof(struct acpi_dhdr),
                                                                   VM_PROT_READ);
 
-        /* Check if the entry contains an APIC. */
+        /* Check if the entry is a MADT */
         check_signature = acpi_check_signature(descr_header->signature, ACPI_APIC_SIG, 4*sizeof(uint8_t));
+        if (check_signature == ACPI_SUCCESS)
+            madt = (struct acpi_apic*) descr_header;
 
+        /* Check if the entry is a HPET */
+        check_signature = acpi_check_signature(descr_header->signature, ACPI_HPET_SIG, 4*sizeof(uint8_t));
         if (check_signature == ACPI_SUCCESS) {
-            /* If yes, return the APIC. */
-            return (struct acpi_apic*) descr_header;
+            map_addr = ((struct acpi_hpet *)descr_header)->address.addr64;
+            assert (map_addr != 0);
+            hpet_addr = (uint32_t *)kmem_map_aligned_table(map_addr, 1024, VM_PROT_READ | VM_PROT_WRITE);
+            printf("HPET at physical address 0x%llx\n", map_addr);
         }
     }
 
-    return NULL;
+    return madt;
 }
 
 /*
@@ -323,28 +333,37 @@ acpi_get_apic(struct acpi_rsdt *rsdt, int acpi_rsdt_n)
  * and the number of entries of XSDT table.
  *
  * Returns a reference to APIC/MADT table if success, NULL if failure.
+ * Also sets hpet_addr to base address of HPET.
  */
 static struct acpi_apic*
 acpi_get_apic2(struct acpi_xsdt *xsdt, int acpi_xsdt_n)
 {
     struct acpi_dhdr *descr_header;
+    struct acpi_apic *madt = NULL;
     int check_signature;
+    uint64_t map_addr;
 
     /* Search APIC entries in rsdt table. */
     for (int i = 0; i < acpi_xsdt_n; i++) {
         descr_header = (struct acpi_dhdr*) kmem_map_aligned_table(xsdt->entry[i], sizeof(struct acpi_dhdr),
                                                                   VM_PROT_READ);
 
-        /* Check if the entry contains an APIC. */
+        /* Check if the entry is an APIC. */
         check_signature = acpi_check_signature(descr_header->signature, ACPI_APIC_SIG, 4*sizeof(uint8_t));
+        if (check_signature == ACPI_SUCCESS)
+            madt = (struct acpi_apic *)descr_header;
 
+        /* Check if the entry is a HPET. */
+        check_signature = acpi_check_signature(descr_header->signature, ACPI_HPET_SIG, 4*sizeof(uint8_t));
         if (check_signature == ACPI_SUCCESS) {
-            /* If yes, return the APIC. */
-            return (struct acpi_apic*) descr_header;
+            map_addr = ((struct acpi_hpet *)descr_header)->address.addr64;
+            assert (map_addr != 0);
+            hpet_addr = (uint32_t *)kmem_map_aligned_table(map_addr, 1024, VM_PROT_READ | VM_PROT_WRITE);
+            printf("HPET at physical address 0x%llx\n", map_addr);
         }
     }
 
-    return NULL;
+    return madt;
 }
 
 /*
diff --git a/i386/i386at/acpi_parse_apic.h b/i386/i386at/acpi_parse_apic.h
index df36bb31..85e01170 100644
--- a/i386/i386at/acpi_parse_apic.h
+++ b/i386/i386at/acpi_parse_apic.h
@@ -91,6 +91,14 @@ struct acpi_xsdt {
     uint64_t 			entry[0];
 } __attribute__((__packed__));
 
+struct acpi_address {
+    uint8_t	is_io;
+    uint8_t	reg_width;
+    uint8_t	reg_offset;
+    uint8_t	reserved;
+    uint64_t	addr64;
+} __attribute__((__packed__));
+
 /* APIC table signature. */
 #define ACPI_APIC_SIG "APIC"
 
@@ -170,6 +178,21 @@ struct acpi_apic_irq_override {
     uint16_t    flags;
 } __attribute__((__packed__));
 
+
+#define ACPI_HPET_SIG "HPET"
+
+/*
+ * HPET High Precision Event Timer structure
+ */
+struct acpi_hpet {
+    struct acpi_dhdr header;
+    uint32_t	id;
+    struct acpi_address	address;
+    uint8_t	sequence;
+    uint16_t	minimum_tick;
+    uint8_t	flags;
+} __attribute__((__packed__));
+
 int acpi_apic_init(void);
 void acpi_print_info(phys_addr_t rsdp, void *rsdt, int acpi_rsdt_n);
 
diff --git a/i386/i386at/model_dep.c b/i386/i386at/model_dep.c
index 173b99f5..789271fd 100644
--- a/i386/i386at/model_dep.c
+++ b/i386/i386at/model_dep.c
@@ -221,6 +221,7 @@ void machine_init(void)
 	 */
 	/* FIXME: this may not allocate from below 1MB, if within first 16MB */
 	apboot_addr = vm_page_to_pa(vm_page_grab_contig(PAGE_SIZE, VM_PAGE_SEL_DMA));
+	apboot_addr = 0x3000;
 	assert (apboot_addr < 0x100000);
 
 	/*
@@ -229,6 +230,11 @@ void machine_init(void)
 	 */
 	gdt_descr_tmp.linear_base += apboot_addr;
 	apboot_jmp_offset += apboot_addr;
+
+	/*
+	 * Initialize the HPET
+	 */
+	hpet_init();
 #endif
 }