[efi] Use a timer event to generate the currticks() timer

We currently use the EFI_CPU_ARCH_PROTOCOL's GetTimerValue() method to
generate the currticks() timer, calibrated against a 1ms delay from
the boot services Stall() method.

This does not work on ARM platforms, where GetTimerValue() is an empty
stub which just returns EFI_UNSUPPORTED.

Fix by instead creating a periodic timer event, and using this event
to increment a current tick counter.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 68 insertions, 50 deletions

diff --git a/src/interface/efi/efi_timer.c b/src/interface/efi/efi_timer.c
index 81620c92..a574e204 100644
--- a/src/interface/efi/efi_timer.c
+++ b/src/interface/efi/efi_timer.c
@@ -25,12 +25,10 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 #include <string.h>
 #include <errno.h>
-#include <limits.h>
-#include <assert.h>
 #include <unistd.h>
 #include <ipxe/timer.h>
+#include <ipxe/init.h>
 #include <ipxe/efi/efi.h>
-#include <ipxe/efi/Protocol/Cpu.h>
 
 /** @file
  *
@@ -38,19 +36,14 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  *
  */
 
-/** Scale factor to apply to CPU timer 0
- *
- * The timer is scaled down in order to ensure that reasonable values
- * for "number of ticks" don't exceed the size of an unsigned long.
- */
-#define EFI_TIMER0_SHIFT 12
+/** Current tick count */
+static unsigned long efi_jiffies;
 
-/** Calibration time */
-#define EFI_CALIBRATE_DELAY_MS 1
+/** Timer tick event */
+static EFI_EVENT efi_tick_event;
 
-/** CPU protocol */
-static EFI_CPU_ARCH_PROTOCOL *cpu_arch;
-EFI_REQUIRE_PROTOCOL ( EFI_CPU_ARCH_PROTOCOL, &cpu_arch );
+/** Colour for debug messages */
+#define colour &efi_jiffies
 
 /**
  * Delay for a fixed number of microseconds
@@ -64,8 +57,8 @@ static void efi_udelay ( unsigned long usecs ) {
 
 	if ( ( efirc = bs->Stall ( usecs ) ) != 0 ) {
 		rc = -EEFI ( efirc );
-		DBG ( "EFI could not delay for %ldus: %s\n",
-		      usecs, strerror ( rc ) );
+		DBGC ( colour, "EFI could not delay for %ldus: %s\n",
+		       usecs, strerror ( rc ) );
 		/* Probably screwed */
 	}
 }
@@ -76,53 +69,78 @@ static void efi_udelay ( unsigned long usecs ) {
  * @ret ticks		Current time, in ticks
  */
 static unsigned long efi_currticks ( void ) {
-	UINT64 time;
+
+	return efi_jiffies;
+}
+
+/**
+ * Timer tick
+ *
+ * @v event		Timer tick event
+ * @v context		Event context
+ */
+static EFIAPI void efi_tick ( EFI_EVENT event __unused,
+			      void *context __unused ) {
+
+	/* Increment tick count */
+	efi_jiffies++;
+}
+
+/**
+ * Start timer tick
+ *
+ */
+static void efi_tick_startup ( void ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	EFI_STATUS efirc;
 	int rc;
 
-	/* Read CPU timer 0 (TSC) */
-	if ( ( efirc = cpu_arch->GetTimerValue ( cpu_arch, 0, &time,
-						 NULL ) ) != 0 ) {
+	/* Create timer tick event */
+	if ( ( efirc = bs->CreateEvent ( ( EVT_TIMER | EVT_NOTIFY_SIGNAL ),
+					 TPL_CALLBACK, efi_tick, NULL,
+					 &efi_tick_event ) ) != 0 ) {
 		rc = -EEFI ( efirc );
-		DBG ( "EFI could not read CPU timer: %s\n", strerror ( rc ) );
-		/* Probably screwed */
-		return -1UL;
+		DBGC ( colour, "EFI could not create timer tick: %s\n",
+		       strerror ( rc ) );
+		/* Nothing we can do about it */
+		return;
 	}
 
-	return ( time >> EFI_TIMER0_SHIFT );
+	/* Start timer tick */
+	if ( ( efirc = bs->SetTimer ( efi_tick_event, TimerPeriodic,
+				      ( 10000000 / EFI_TICKS_PER_SEC ) ) ) !=0){
+		rc = -EEFI ( efirc );
+		DBGC ( colour, "EFI could not start timer tick: %s\n",
+		       strerror ( rc ) );
+		/* Nothing we can do about it */
+		return;
+	}
+	DBGC ( colour, "EFI timer started at %d ticks per second\n",
+	       EFI_TICKS_PER_SEC );
 }
 
 /**
- * Get number of ticks per second
+ * Stop timer tick
  *
- * @ret ticks_per_sec	Number of ticks per second
+ * @v booting		System is shutting down in order to boot
  */
-static unsigned long efi_ticks_per_sec ( void ) {
-	static unsigned long ticks_per_sec = 0;
-
-	/* Calibrate timer, if necessary.  EFI does nominally provide
-	 * the timer speed via the (optional) TimerPeriod parameter to
-	 * the GetTimerValue() call, but it gets the speed slightly
-	 * wrong.  By up to three orders of magnitude.  Not helpful.
-	 */
-	if ( ! ticks_per_sec ) {
-		unsigned long start;
-		unsigned long elapsed;
-
-		DBG ( "Calibrating EFI timer with a %d ms delay\n",
-		      EFI_CALIBRATE_DELAY_MS );
-		start = currticks();
-		mdelay ( EFI_CALIBRATE_DELAY_MS );
-		elapsed = ( currticks() - start );
-		ticks_per_sec = ( elapsed * ( 1000 / EFI_CALIBRATE_DELAY_MS ));
-		DBG ( "EFI CPU timer calibrated at %ld ticks in %d ms (%ld "
-		      "ticks/sec)\n", elapsed, EFI_CALIBRATE_DELAY_MS,
-		      ticks_per_sec );
-	}
+static void efi_tick_shutdown ( int booting __unused ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 
-	return ticks_per_sec;
+	/* Stop timer tick */
+	bs->SetTimer ( efi_tick_event, TimerCancel, 0 );
+	DBGC ( colour, "EFI timer stopped\n" );
+
+	/* Destroy timer tick event */
+	bs->CloseEvent ( efi_tick_event );
 }
 
+/** Timer tick startup function */
+struct startup_fn efi_tick_startup_fn __startup_fn ( STARTUP_EARLY ) = {
+	.startup = efi_tick_startup,
+	.shutdown = efi_tick_shutdown,
+};
+
 PROVIDE_TIMER ( efi, udelay, efi_udelay );
 PROVIDE_TIMER ( efi, currticks, efi_currticks );
-PROVIDE_TIMER ( efi, ticks_per_sec, efi_ticks_per_sec );
+PROVIDE_TIMER_INLINE ( efi, ticks_per_sec );