Initial commit

src/hal/tsc.c

@@ -0,0 +1,77 @@
+#include <cpuid.h>
+#include <stdio.h>
+#include <stdint.h>
+#include "error.h"
+#include "../drivers/pmt.h"
+
+uint32_t core_crystal_clock = 0;
+
+void enable_tsc(){
+    asm(".intel_syntax noprefix\n\
+        mov rax, cr4\n\
+        or rax, 0b10\n\
+        mov cr4, rax\n\
+        .att_syntax prefix");
+}
+
+void disable_tsc(){
+    asm(".intel_syntax noprefix\n\
+        mov rax, cr4\n\
+        and rax, 0xFFFFFFFFFFFFFFFD\n\
+        mov cr4, rax\n\
+        .att_syntax prefix");
+}
+
+uint64_t read_tsc(){
+    uint32_t eax, edx;
+    asm("rdtsc" :"=a"(eax),"=d"(edx));
+    return ((uint64_t)edx << 32 | eax);
+}
+
+kstatus tsc_init(){
+
+    uint32_t edx, unused;
+
+    /* Check if there is an invariant TSC */
+    __get_cpuid(0x80000007, &unused, &unused, &unused, &edx);
+
+    if((edx & (1 << 8)) == 0){
+        return KERNEL_STATUS_ERROR;
+    }
+
+    kprintf("tsc: Invariant TSC found\n");
+
+    /* Get the core crystal clock so we can determine TSC speed */
+    __get_cpuid(0x15, &unused, &unused, &core_crystal_clock, &unused);
+
+    if(core_crystal_clock != 0){
+        kprintf("cpuid 15h supported!\n");
+
+        /* Make it so that it ticks every millisecond */
+        core_crystal_clock *= 1000;
+
+    }else{
+        /* Calibrate using the PMT */
+        enable_tsc();
+        uint32_t read1 = read_tsc();
+        pmt_delay(1000);
+        uint32_t read2 = read_tsc();
+        disable_tsc();
+        core_crystal_clock = read2 - read1;
+    }
+
+    kprintf("Core crystal clock: {d}\n", core_crystal_clock);
+
+    enable_tsc();
+
+    return KERNEL_STATUS_SUCCESS;
+
+}
+
+uint64_t tsc_get_timestamp(){
+    if(core_crystal_clock == 0){
+        return 0;
+    }
+    uint64_t read = read_tsc();
+    return read / core_crystal_clock;
+}