diff options
| -rw-r--r-- | kernel/start.c | 34 | ||||
| -rw-r--r-- | kernel/uart.c | 5 |
2 files changed, 27 insertions, 12 deletions
diff --git a/kernel/start.c b/kernel/start.c index 0f3453d..203c5e6 100644 --- a/kernel/start.c +++ b/kernel/start.c @@ -5,6 +5,7 @@ #include "defs.h" void main(); +void timerinit(); // entry.S needs one stack per CPU. __attribute__ ((aligned (16))) char stack0[4096 * NCPU]; @@ -36,15 +37,31 @@ start() w_medeleg(0xffff); w_mideleg(0xffff); + // ask for clock interrupts. + timerinit(); + + // keep each CPU's hartid in its tp register, for cpuid(). + int id = r_mhartid(); + w_tp(id); + + // switch to supervisor mode and jump to main(). + asm volatile("mret"); +} + +// set up to receive timer interrupts in machine mode, +// which arrive at timervec in kernelvec.S, +// which turns them into software interrupts for +// devintr() in trap.c. +void +timerinit() +{ + // each CPU has a separate source of timer interrupts. int id = r_mhartid(); - // set up to receive timer interrupts in machine mode, - // which arrive at timervec in kernelvec.S, - // which turns them into software interrupts for - // devintr() in trap.c. // ask the CLINT for a timer interrupt. int interval = 1000000; // cycles; about 1/10th second in qemu. *(uint64*)CLINT_MTIMECMP(id) = *(uint64*)CLINT_MTIME + interval; + // prepare information in scratch[] for timervec. // scratch[0..3] : space for timervec to save registers. // scratch[4] : address of CLINT MTIMECMP register. @@ -53,16 +70,13 @@ start() scratch[4] = CLINT_MTIMECMP(id); scratch[5] = interval; w_mscratch((uint64)scratch); + // set the machine-mode trap handler. w_mtvec((uint64)timervec); + // enable machine-mode interrupts. w_mstatus(r_mstatus() | MSTATUS_MIE); + // enable machine-mode timer interrupts. w_mie(r_mie() | MIE_MTIE); - - // keep each CPU's hartid in its tp register, for cpuid(). - w_tp(id); - - // switch to supervisor mode and jump to main(). - asm volatile("mret"); } diff --git a/kernel/uart.c b/kernel/uart.c index 852a085..3a5cdc4 100644 --- a/kernel/uart.c +++ b/kernel/uart.c @@ -15,8 +15,9 @@ // address of one of the registers. #define Reg(reg) ((volatile unsigned char *)(UART0 + reg)) -// the registers. some have different meanings for -// read and write. +// the UART control registers. +// some have different meanings for +// read vs write. // http://byterunner.com/16550.html #define RHR 0 // receive holding register (for input bytes) #define THR 0 // transmit holding register (for output bytes) |