From 9dabe01545644dd78448d8d489616872f14d964b Mon Sep 17 00:00:00 2001
From: Miguel <m.i@gmx.at>
Date: Sun, 9 Sep 2018 00:26:30 +0200
Subject: lapic bus speed probing and starting switch to ioapic

---
 kernel/smp.c | 58 +++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 41 insertions(+), 17 deletions(-)

(limited to 'kernel/smp.c')

diff --git a/kernel/smp.c b/kernel/smp.c
index da91148..b2ce6b0 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -43,6 +43,7 @@ volatile uint8_t proc;
 uint32_t cpu_counter[SMP_MAX_PROC];
 
 uint32_t local_apic_addr;
+uint32_t countdown;
 
 void writeAPIC(uint32_t offset, uint32_t value)
 {
@@ -81,6 +82,35 @@ void apicEnable()
 
 }
 
+/** select mode : divisor.
+ * 0 - 1
+ * 1 - 2
+ * 2 - 4
+ * 3 - 8
+ * 4 - 16
+ * 5 - 32
+ * 6 - 64
+ * 7 - 128
+ */
+
+uint32_t probeBusSpeed(uint32_t sel)
+{
+    uint32_t div[]={1,2,4,8,16,32,64,128};
+    uint32_t reg[]={0b1011,0,1,2,3,0b1000,0b1001,0b1010};
+
+    uint32_t divisor=div[sel];
+
+    klog("Probing bus speed for 50ms (div=%d)) ...",divisor);
+    writeAPIC(APIC_TMRDIV, reg[sel]);
+    writeAPIC(APIC_TMRINITCNT, 0xFFFFFFFF);
+//    for(int i=0;i<20;i++)
+	asm_pit_sleep_50ms();
+    //writeAPIC(APIC_LVT_TMR, APIC_LVT_INT_MASKED); //??
+    uint32_t ticksInS = 0xFFFFFFFF - readAPIC(APIC_TMRCURRCNT);
+    ticksInS*=20; // adjust to one full second.
+    klog("%d MHz (%d Hz) bus speed (ticks=%d)",ticksInS/(1000000/divisor),ticksInS*divisor,ticksInS/20);
+    return ticksInS*divisor;
+}
 void smp_main()
 {
     // setup stack
@@ -99,7 +129,6 @@ void kernel_ap()
     int_install();
     gdt_init();
     
-    uint32_t countdown=0x0fffffff; // TODO: calc to be constant, depending on bus speed. (use pit for measurement?)
     writeAPIC(APIC_TMRDIV, 0x3);
     writeAPIC(APIC_LVT_TMR, 200 | TMR_PERIODIC);
     writeAPIC(APIC_TMRINITCNT, countdown);
@@ -151,9 +180,18 @@ void smp_start_aps(smp_processors *pros)
 {
         // TODO: check if local APIC is present via CPUID (P6 (i686) and above)
 	local_apic_addr=pros->local_apic_address;
-
 	klog("bsp local apic id: 0x%08X",apicID());
 
+	apicEnable(); // bsp apic seems to be enabled anyway.
+
+	uint32_t speed=probeBusSpeed(4); // get bus speed (divisor: 16)
+
+	// setup apic timer
+	countdown=speed/16; // tick once a second
+	writeAPIC(APIC_TMRDIV, 0x3); // divisor 16
+	writeAPIC(APIC_LVT_TMR, 200 | TMR_PERIODIC); // on interrupt 200
+	writeAPIC(APIC_TMRINITCNT, countdown);
+
         for(int i=0;i<pros->processors;i++)
 	{
 	    if(pros->boot==i)continue;
@@ -177,19 +215,5 @@ void smp_start_aps(smp_processors *pros)
 	    // TODO retry 110 SIPI with 1s timeout
 	    
 	}
-
-    apicEnable(); // bsp seems to be enabled anyway.
-    
-    writeAPIC(APIC_TMRDIV, 0x3);
-    writeAPIC(APIC_TMRINITCNT, 0xFFFFFFFF);
-    //asm_pit_sleep_1ms();
-    //writeAPIC(APIC_LVT_TMR, APIC_LVT_INT_MASKED); //??
-    uint32_t ticksInS = 0xFFFFFFFF - readAPIC(APIC_TMRCURRCNT);
-
-    klog("%d MHz bus speed",ticksInS/1000);
-
-    uint32_t countdown=0x0fffffff; // TODO: calc to be constant, depending on bus speed. (use pit for measurement?)
-    writeAPIC(APIC_TMRDIV, 0x3);
-    writeAPIC(APIC_LVT_TMR, 200 | TMR_PERIODIC);
-    writeAPIC(APIC_TMRINITCNT, countdown);
 }
+
-- 
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