src/cpu/x86/lapic/lapic_cpu_stop.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <console/console.h>
   4 #include <cpu/x86/lapic.h>
   5 #include <delay.h>
   6 #include <halt.h>
   7 #include <stdint.h>
   8
   9 /**
  10  * Sending INIT IPI to self is equivalent of asserting #INIT with a bit of
  11  * delay.
  12  * An undefined number of instruction cycles will complete. All global locks
  13  * must be released before INIT IPI and no printk is allowed after this.
  14  * De-asserting INIT IPI is a no-op on later Intel CPUs.
  15  *
  16  * If you set DEBUG_HALT_SELF to 1, printk's after INIT IPI are enabled
  17  * but running thread may halt without releasing the lock and effectively
  18  * deadlock other CPUs.
  19  */
  20 #define DEBUG_HALT_SELF 0
  21
  22 #if DEBUG_HALT_SELF
  23 #define dprintk(LEVEL, args...) do { printk(LEVEL, ##args); } while (0)
  24 #else
  25 #define dprintk(LEVEL, args...) do { } while (0)
  26 #endif
  27
  28 static void wait_for_ipi_completion_without_printk(const int timeout_ms)
  29 {
  30         int loops = timeout_ms * 10;
  31         uint32_t send_status;
  32
  33         /* wait for the ipi send to finish */
  34         dprintk(BIOS_SPEW, "Waiting for send to finish...\n");
  35         do {
  36                 dprintk(BIOS_SPEW, "+");
  37                 udelay(100);
  38                 send_status = lapic_busy();
  39         } while (send_status && (--loops > 0));
  40
  41         if (send_status)
  42                 dprintk(BIOS_ERR, "timed out\n");
  43 }
  44
  45 /**
  46  * Normally this function is defined in lapic.h as an always inline function
  47  * that just keeps the CPU in a hlt() loop. This does not work on all CPUs.
  48  * I think all hyperthreading CPUs might need this version, but I could only
  49  * verify this on the Intel Core Duo
  50  */
  51 void stop_this_cpu(void)
  52 {
  53         const int timeout_100ms = 100;
  54         unsigned long id = lapicid();
  55
  56         printk(BIOS_DEBUG, "CPU %ld going down...\n", id);
  57
  58         /* send an LAPIC INIT to myself */
  59         lapic_send_ipi_self(LAPIC_INT_LEVELTRIG | LAPIC_INT_ASSERT | LAPIC_DM_INIT);
  60         wait_for_ipi_completion_without_printk(timeout_100ms);
  61
  62         mdelay(10);
  63
  64         dprintk(BIOS_SPEW, "Deasserting INIT.\n");
  65
  66         /* Deassert the LAPIC INIT */
  67         lapic_send_ipi_self(LAPIC_INT_LEVELTRIG | LAPIC_DM_INIT);
  68         wait_for_ipi_completion_without_printk(timeout_100ms);
  69
  70         halt();
  71 }