demo of arm timer irq

5 files changed, 78 insertions, 31 deletions

diff --git a/PL0_test.c b/PL0_test.c
index ac74ad4..c6cbe18 100644
--- a/PL0_test.c
+++ b/PL0_test.c
@@ -5,25 +5,30 @@ void PL0_main(void)
 {
   // If loading program to userspace and handling of svc are
   // implemented correctly, this shall get printed
-  puts("Hello userspace!");
+  puts("Hello userspace! Type 'f' if you want me to try accessing "
+       "kernel memory!");
   
-  // if we're indeed in PL0, we should trigger the abort handler now,
-  // when trying to access memory we're not allowed to
-  puts("Attempting to meddle with kernel memory from userspace :d");
-  char first_kernel_byte[2];
-
-  first_kernel_byte[0] = *(char*) 0x0;
-  first_kernel_byte[1] = '\0';
-
-  puts(first_kernel_byte);
-    
   while (1)
     {
       char c = getchar();
       
       if (c == '\r')
 	putchar('\n');
-
+      
       putchar(c);
+      
+      if (c == 'f')
+	{
+	  // if we're indeed in PL0, we should trigger the abort
+	  // handler now, when trying to access memory we're not
+	  // allowed to
+	  puts("Attempting to read kernel memory from userspace :d");
+	  char first_kernel_byte[2];
+
+	  first_kernel_byte[0] = *(char*) 0x0;
+	  first_kernel_byte[1] = '\0';
+
+	  puts(first_kernel_byte);
+	}
     }
 }
diff --git a/armclock.h b/armclock.h
index 67a4ab8..700879a 100644
--- a/armclock.h
+++ b/armclock.h
@@ -1,6 +1,8 @@
 #ifndef ARMCLOCK_H
 #define ARMCLOCK_H
 
+#include <stdint.h>
+
 #include "global.h"
 
 #define ARMCLK_LOAD                      (ARM_BASE + 0x400)
@@ -15,35 +17,56 @@
 #define ARMCLK_LOAD_FREE_RUNNING_COUNTER (ARM_BASE + 0x420)
 
 #define BCMCLK_ENABLE_BASIC_IRQS  (ARM_BASE + 0x218)
+#define BCMCLK_DISABLE_BASIC_IRQS (ARM_BASE + 0x224)
 
-static inline void armclk_enable_timer_irq(void)
+typedef union armclk_control
 {
-  //  uint32_t control_reg = *(uint32_t volatile*) ARMCLK_CONTROL;
-  //  control_reg |= 1 << 5;
-  //  *(uint32_t volatile*) ARMCLK_CONTROL = control_reg;
-  *(uint32_t volatile*) ARMCLK_CONTROL = 0x00000000;
-  *(uint32_t volatile*) ARMCLK_LOAD_PRE_DRIVER = 0x000000f9;
-  *(uint32_t volatile*) ARMCLK_LOAD_RELOAD = 0x4C4B40; //50 times a Sec by 250Mhz
-  *(uint32_t volatile*) ARMCLK_LOAD = 0x4C4B40;//50 times a Sec by 250Mhz
-  *(uint32_t volatile*) ARMCLK_IRQ_CLR_ACK = 0x00000000;
-  *(uint32_t volatile*) ARMCLK_CONTROL = 0x000000a2;
-
+  uint32_t raw;
+  struct
+  {
+    uint32_t one_shot_mode           : 1; // bit  0; unused in RPi
+    uint32_t counter_23bit           : 1; // bit  1
+    uint32_t pre_scale               : 2; // bits 3:2
+    uint32_t bit_4                   : 1; // bit  4
+    uint32_t interrupt_enable        : 1; // bit  5
+    uint32_t periodic_mode           : 1; // bit  6; unused in RPi
+    uint32_t timer_enable            : 1; // bit  7
+    uint32_t halt_in_debug           : 1; // bit  8
+    uint32_t free_running_enable     : 1; // bit  9
+    uint32_t bits_15_10              : 6; // bits 15:10
+    uint32_t free_running_pre_scaler : 8; // bits 23:16
+    uint32_t bits_31_24              : 8; // bits 31:24
+  } fields;
+} armclk_control_t;
 
+static inline void armclk_init(void)
+{
+  armclk_control_t ctrl = (armclk_control_t) (uint32_t) 0;
+  ctrl.fields.timer_enable = 1;
+  ctrl.fields.interrupt_enable = 1;
+  ctrl.fields.counter_23bit = 1;
+  *(uint32_t volatile*) ARMCLK_CONTROL = ctrl.raw;
+}
 
-  
+static inline void armclk_enable_timer_irq(void)
+{
   *(uint32_t volatile*) BCMCLK_ENABLE_BASIC_IRQS = 1;
 }
 
 static inline void armclk_disable_timer_irq(void)
 {
-  uint32_t control_reg = *(uint32_t volatile*) ARMCLK_CONTROL;
-  control_reg &= ~((uint32_t) 1 << 5);
-  *(uint32_t volatile*) ARMCLK_CONTROL = control_reg;
+  *(uint32_t volatile*) BCMCLK_DISABLE_BASIC_IRQS = 1;
 }
 
 static inline void armclk_set_timer_match_timeout(uint32_t timeout)
 {
+  *(uint32_t volatile*) ARMCLK_IRQ_CLR_ACK = 0;
   *(uint32_t volatile*) ARMCLK_LOAD = timeout;
 }
 
+static inline _Bool armclk_irq_pending(void)
+{
+  return *(uint32_t volatile*) ARMCLK_LOAD_RAW_IRQ;
+}
+
 #endif // ARMCLOCK_H
diff --git a/demo_functionality.c b/demo_functionality.c
index 3cf5b8f..a2d8550 100644
--- a/demo_functionality.c
+++ b/demo_functionality.c
@@ -5,6 +5,7 @@
 #include "ramfs.h"
 #include "strings.h"
 #include "paging.h"
+#include "armclock.h"
 
 void demo_paging_support(void)
 {
@@ -120,10 +121,13 @@ void demo_go_unprivileged(void)
 
   PSR_t new_SPSR = read_CPSR();
   new_SPSR.fields.PSR_MODE_4_0 = MODE_USER;
+  new_SPSR.fields.PSR_IRQ_MASK_BIT = 0;
   write_SPSR(new_SPSR);
 
   puts("All ready, jumping to PL0 code");
 
+  armclk_set_timer_match_timeout(0x00100000);
+  
   asm volatile("cps %[sysmode]\n\r"
 	       "mov sp, %[stackaddr]\n\r"
 	       "cps %[supmode]\n\r"
diff --git a/interrupts.c b/interrupts.c
index c6e3f17..62c644b 100644
--- a/interrupts.c
+++ b/interrupts.c
@@ -1,5 +1,6 @@
 #include "io.h"
 #include "svc_interface.h"
+#include "armclock.h"
 
 void __attribute__((noreturn)) setup(void);
 
@@ -58,9 +59,16 @@ void generic_handler(void)
 
 void irq_handler(void)
 {
-  puts("irq happened");
-
-  while(1);
+  if (armclk_irq_pending())
+    {
+      puts("<<irq from timer>>");
+      armclk_set_timer_match_timeout(0x00100000);
+    }
+  else
+    {
+      puts("unknown irq");
+      while(1);
+    }
 }
 
 void fiq_handler(void)
diff --git a/setup.c b/setup.c
index 63ca054..ad01720 100644
--- a/setup.c
+++ b/setup.c
@@ -5,6 +5,7 @@
 #include "atags.h"
 // for POWER_OF_2() macro... perhaps the macro should be moved
 #include "memory.h"
+#include "armclock.h"
 
 void setup(uint32_t r0, uint32_t machine_type,
 	   struct atag_header *atags)
@@ -14,7 +15,7 @@ void setup(uint32_t r0, uint32_t machine_type,
   // When we attach screen session after loading kernel with socat
   // we miss kernel's greeting... So we'll make the kernel wait for
   // one char we're going to send from within screen
-  //getchar();
+  getchar();
   
   puts("Hello, kernel World!");
 
@@ -97,6 +98,12 @@ void setup(uint32_t r0, uint32_t machine_type,
   // loads a blob there 
   demo_setup_PL0();
 
+  // sets some general settings for arm timer
+  armclk_init();
+
+  // turns on irq from arm timer
+  armclk_enable_timer_irq();
+
   // jumps to unprivileged code... never, ever, ever returns
   demo_go_unprivileged();