[CX II] Implement sleep mode

With this, it's possible to turn the calculator back on after it went into
sleep mode (idle timeout or explicitly turned off).

What happens when pressing On is that the calc starts from bootrom again, but
that finds fastboot data in the 90030000 area left by the OS and uses that to
validate some state and jumps back to the OS code in SDRAM.

Add a TODO entry to improve fastboot data handling. Currently the data is
preserved across restarts, which means that some possibly incompatible bootrom
tries to interpret it. So far the validation detects that SDRAM was cleared and
aborts.

Author: Vogtinator

TODO.md

@@ -13,7 +13,11 @@
 * Better debugger integration
 * Don't use a 60Hz timer for LCD redrawing, hook lcd_event instead
 * Less global vars (emu.h), move into structs
-* Use streams for reading/writing snapshots instead of struct emu_snapshot 
+* Use streams for reading/writing snapshots instead of struct emu_snapshot
+* Fastboot data is currently not cleared at all, it survives soft and hard
+  resets as well as restarts. This was the simplest way to get installers to
+  work, which require that state is persisted across software resets. Ideally,
+  fastboot data is cleared on hardware resets and restarts.
 
 ##Wishlist:
 * Skin loader/switcher

core/cpu.cpp

@@ -432,6 +432,17 @@ void set_reg_bx(uint8_t i, uint32_t value)
     }
 }
 
+void cpu_reset()
+{
+    memset(&arm, 0, sizeof arm);
+    arm.control = 0x00050078;
+    arm.cpsr_low28 = MODE_SVC | 0xC0;
+    cpu_events &= EVENT_DEBUG_STEP;
+
+    addr_cache_flush();
+    flush_translations();
+}
+
 bool cpu_resume(const emu_snapshot *s)
 {
     return snapshot_read(s, &arm, sizeof(arm))

core/cpu.h

@@ -84,6 +84,7 @@ extern struct arm_state arm __asm__("arm");
 #endif
 
 typedef struct emu_snapshot emu_snapshot;
+void cpu_reset(); // Essentially a soft reset
 bool cpu_resume(const emu_snapshot *s);
 bool cpu_suspend(emu_snapshot *s);
 void cpu_int_check();

core/cx2.cpp

@@ -77,7 +77,7 @@ void aladdin_pmu_write(uint32_t addr, uint32_t value)
 			if(value & 2)
 			{
 				/* enter sleep, jump to 0 when On pressed. */
-				warn("Sleep not implemented");
+				cpu_events |= EVENT_SLEEP;
 				// Without this, the clocks are wrong
 				aladdin_pmu_reset();
 			}

core/emu.cpp

@@ -348,6 +348,12 @@ void emu_loop(bool reset)
                 goto reset;
             }
 
+            if (cpu_events & EVENT_SLEEP) {
+                assert(emulate_cx2);
+                cycle_count_delta = 0;
+                break;
+            }
+
             if (cpu_events & (EVENT_FIQ | EVENT_IRQ)) {
                 // Align PC in case the interrupt occurred immediately after a jump
                 if (arm.cpsr_low28 & 0x20)

core/emu.h

@@ -33,6 +33,7 @@ extern uint32_t cpu_events __asm__("cpu_events");
 #define EVENT_RESET 4
 #define EVENT_DEBUG_STEP 8
 #define EVENT_WAITING 16
+#define EVENT_SLEEP 32
 
 // Settings
 extern bool exiting, debug_on_start, debug_on_warn, print_on_warn;

core/keypad.cpp

@@ -33,6 +33,11 @@ void keypad_on_pressed() {
     // TODO: The CX II may have an enable bit somewhere
     if(!emulate_cx2 && pmu.on_irq_enabled)
         int_set(INT_POWER, true);
+
+    if(cpu_events & EVENT_SLEEP) {
+        assert(emulate_cx2);
+        cpu_reset();
+    }
 }
 
 uint32_t keypad_read(uint32_t addr) {

core/misc.c

@@ -245,9 +245,15 @@ void timer_reset() {
 static fastboot_state fastboot;
 
 uint32_t fastboot_cx_read(uint32_t addr) {
+    if((addr & 0xFFFF) >= 0x1000)
+        return bad_read_word(addr); // On HW it repeats
+
     return fastboot.mem[(addr & 0xFFF) >> 2];
 }
 void fastboot_cx_write(uint32_t addr, uint32_t value) {
+    if((addr & 0xFFFF) >= 0x1000)
+        return bad_write_word(addr, value);
+
     // TODO: This isn't cleared on resets, but should be cleared
     // eventually, probably on restarts?
     fastboot.mem[(addr & 0xFFF) >> 2] = value;