ARM: kernel: fix timer resolution and implement basic timekeeping.

The previously used method for programming the timer did not take
into account that our timespec is 64bit while the register we poke
it into is 32 bit. Since the PXA (SoC in Verdex target) has a limited
scale of resolution (us,ms,second) we dynamicly determine the one
that we can most closely match, and set that.

For f.ex. snooze to work however, we also need system_time to work.
The current implementation uses a system timer at microsecond
resolution to keep track of time.

Although the code is far from perfect, committing it now before
it gets lost, since I'm working on the infrastructure code
to properly factor out the SoC specific code out of the core
ARM architecture code (so the kernel can support more then
our poor old Verdex QEMU target ;))

src/system/kernel/arch/arm/arch_timer.cpp

@@ -35,35 +35,63 @@
 #define PXA_OSSR		0x05
 #define PXA_OIER		0x07
 #define PXA_OSCR4		0x10
+#define PXA_OSCR5		0x11
 #define PXA_OSMR4		0x20
+#define PXA_OSMR5		0x21
 #define PXA_OMCR4		0x30
+#define PXA_OMCR5		0x31
 
+#define PXA_RES_S	(3 << 0)
+#define PXA_RES_MS	(1 << 1)
+#define PXA_RES_US	(1 << 2)
 
-static area_id sPxaTimersArea;
-static uint32 *sPxaTimersBase;
+#define US2S(bt)	((bt) / 1000000ULL)
+#define US2MS(bt)	((bt) / 1000ULL)
 
+static area_id sPxaTimersArea = B_ERROR;
+static uint32 *sPxaTimersBase = NULL;
+static bigtime_t sSystemTime = 0;
 
 static int32
 pxa_timer_interrupt(void *data)
 {
-	int32 ret = timer_interrupt();
-        sPxaTimersBase[PXA_OSSR] |= (1 << 4);
+	if (sPxaTimersBase[PXA_OSSR] & (1 << 4)) {
+		sPxaTimersBase[PXA_OSSR] |= (1 << 4);
+		return timer_interrupt();
+	}
 
-        return ret;
+	if (sPxaTimersBase[PXA_OSSR]  & (1 << 5)) {
+		sPxaTimersBase[PXA_OSSR] |= (1 << 5);
+		sSystemTime += UINT_MAX + 1ULL;
+	}
+
+	return B_HANDLED_INTERRUPT;
 }
 
-
 void
 arch_timer_set_hardware_timer(bigtime_t timeout)
 {
-	TRACE(("arch_timer_set_hardware_timer(%lld)\n", timeout));
+	uint32 val = timeout & UINT_MAX;
+	uint32 res = PXA_RES_US;
 
-	if (sPxaTimersBase) {
-		sPxaTimersBase[PXA_OIER] |= (1 << 4);
-		sPxaTimersBase[PXA_OMCR4] = 4; // set to exactly single milisecond resolution
-		sPxaTimersBase[PXA_OSMR4] = timeout;
-		sPxaTimersBase[PXA_OSCR4] = 0; // start counting from 0 again
+	if (timeout & ~UINT_MAX) {
+		// Does not fit, so scale resolution down to milliseconds
+		if (US2MS(timeout) & ~UINT_MAX) {
+			// Still does not fit, scale down to seconds as last ditch attempt
+			val = US2S(timeout) & UINT_MAX;
+			res = PXA_RES_S;
+		} else {
+			// Fits in millisecond resolution
+			val = US2MS(timeout) & UINT_MAX;
+			res = PXA_RES_MS;
+		}
 	}
+
+	TRACE(("arch_timer_set_hardware_timer(val=%lu, res=%lu)\n", val, res));
+	sPxaTimersBase[PXA_OIER] |= (1 << 4);
+	sPxaTimersBase[PXA_OMCR4] = res;
+	sPxaTimersBase[PXA_OSMR4] = val;
+	sPxaTimersBase[PXA_OSCR4] = 0; // start counting from 0 again
 }
 
 
@@ -72,13 +100,10 @@ arch_timer_clear_hardware_timer()
 {
 	TRACE(("arch_timer_clear_hardware_timer\n"));
 
-	if (sPxaTimersBase) {
-		sPxaTimersBase[PXA_OMCR4] = 0; // disable our timer
-		sPxaTimersBase[PXA_OIER] &= ~(4 << 1);
-	}
+	sPxaTimersBase[PXA_OMCR4] = 0; // disable our timer
+	sPxaTimersBase[PXA_OIER] &= ~(1 << 4);
 }
 
-
 int
 arch_init_timer(kernel_args *args)
 {
@@ -88,9 +113,20 @@ arch_init_timer(kernel_args *args)
 	if (sPxaTimersArea < 0)
 		return sPxaTimersArea;
 
-	sPxaTimersBase[PXA_OMCR4] = 0; // disable our timer
+	sPxaTimersBase[PXA_OIER] |= (1 << 5); // enable timekeeping timer
+	sPxaTimersBase[PXA_OMCR5] = PXA_RES_US | (1 << 7);
+	sPxaTimersBase[PXA_OSMR5] = UINT_MAX;
+	sPxaTimersBase[PXA_OSCR5] = 0;
 
 	install_io_interrupt_handler(PXA_TIMERS_INTERRUPT, &pxa_timer_interrupt, NULL, 0);
 
 	return B_OK;
 }
+
+bigtime_t
+system_time(void)
+{
+	return (sPxaTimersBase != NULL) ?
+		sSystemTime + sPxaTimersBase[PXA_OSCR5] :
+		0ULL;
+}

src/system/kernel/lib/arch/arm/Jamfile

@@ -11,8 +11,6 @@ SEARCH_SOURCE += [ FDirName $(librootSources) os arch generic ] ;
 KernelMergeObject kernel_os_arch_$(TARGET_ARCH).o :
 	atomic.S
 	byteorder.S
-#	system_time_asm.S
-	system_time.c
 
 	generic_system_time_nsecs.cpp