svn commit: r334479 - head/sys/dev/acpica

[Andriy Gapon]

Author: avg
Date: Fri Jun  1 09:44:23 2018
New Revision: 334479
URL: https://svnweb.freebsd.org/changeset/base/334479

Log:
  call AcpiLeaveSleepStatePrep after re-enabling interrupts
  
  I want to do this change because this call (actually,
  AcpiHwLegacyWakePrep) does a memory allocation and ACPI namespace
  evaluation.  Although it is not very likely to run into any trouble, it
  is still not safe to make those calls with interrupts disabled.
  witness(4) and malloc(9) do not currently check for a context with
  interrupts disabled via intr_disable and we lack a facility for doing
  that.  So, those unsafe operations fly under the radar.  But if
  intr_disable in acpi_EnterSleepState was replaced with spinlock_enter
  (which it probably should be), then witness and malloc would immediately
  complain.
  
  Also, AcpiLeaveSleepStatePrep is documented as called when interrupts
  are enabled.  It used to require disabled interrupts, but that
  requirement was changed a long time ago when support for _BFS and _GTS
  was removed from ACPICA.
  
  The ACPI wakeup sequence is very sensitive to changes. I consider this
  change to be correct, but there can be fallouts from it.
  
  What AcpiHwLegacyWakePrep essentially does is writing a value
  corresponding to S0 into SLP_TYPx bits of PM1 Control Register(s).
  According to ACPI specifications that write should be a NOP as SLP_EN
  bit is not set.  But I see in some chipset specifications that they
  allow to ignore SLP_EN altogether and to act on a change of SLP_TYPx
  alone.
  
  Also, there are a couple of accesses to ACPI hardware before the new
  location of the call to AcpiLeaveSleepStatePrep.  One is to clear the
  power button status and the other is to enable SCI.  So, the move may
  affect the interaction between then OS and ACPI platform.
  
  I have not seen any regressions on my test system, but it's a desktop.
  
  MFC after:	5 weeks

Modified:
  head/sys/dev/acpica/acpi.c

Modified: head/sys/dev/acpica/acpi.c
==============================================================================
--- head/sys/dev/acpica/acpi.c	Fri Jun  1 09:41:15 2018	(r334478)
+++ head/sys/dev/acpica/acpi.c	Fri Jun  1 09:44:23 2018	(r334479)
@@ -2977,8 +2977,6 @@ acpi_EnterSleepState(struct acpi_softc *sc, int state)
 	if (sleep_result == 1 && state != ACPI_STATE_S4)
 	    AcpiWriteBitRegister(ACPI_BITREG_SCI_ENABLE, ACPI_ENABLE_EVENT);
 
-	AcpiLeaveSleepStatePrep(state);
-
 	if (sleep_result == 1 && state == ACPI_STATE_S3) {
 	    /*
 	     * Prevent mis-interpretation of the wakeup by power button
@@ -3007,6 +3005,8 @@ acpi_EnterSleepState(struct acpi_softc *sc, int state)
 	/* call acpi_wakeup_machdep() again with interrupt enabled */
 	acpi_wakeup_machdep(sc, state, sleep_result, 1);
 
+	AcpiLeaveSleepStatePrep(state);
+
 	if (sleep_result == -1)
 		goto backout;
 
@@ -3015,8 +3015,8 @@ acpi_EnterSleepState(struct acpi_softc *sc, int state)
 	    AcpiEnable();
     } else {
 	status = AcpiEnterSleepState(state);
-	AcpiLeaveSleepStatePrep(state);
 	intr_restore(intr);
+	AcpiLeaveSleepStatePrep(state);
 	if (ACPI_FAILURE(status)) {
 	    device_printf(sc->acpi_dev, "AcpiEnterSleepState failed - %s\n",
 			  AcpiFormatException(status));