diff --git a/VersionASM b/VersionASM
index ca30bbd11f092c29b889565ff73bc0336ade9a61..1666ce515fff5310fbf0cbe6716fd5235b2de227 100644
--- a/VersionASM
+++ b/VersionASM
@@ -9,12 +9,12 @@
GBLS Module_ApplicationDate
GBLS Module_HelpVersion
GBLS Module_ComponentName
-Module_MajorVersion SETS "6.32"
-Module_Version SETA 632
+Module_MajorVersion SETS "6.33"
+Module_Version SETA 633
Module_MinorVersion SETS ""
-Module_Date SETS "19 Jan 2020"
-Module_ApplicationDate SETS "19-Jan-20"
+Module_Date SETS "12 Feb 2020"
+Module_ApplicationDate SETS "12-Feb-20"
Module_ComponentName SETS "Kernel"
-Module_FullVersion SETS "6.32"
-Module_HelpVersion SETS "6.32 (19 Jan 2020)"
+Module_FullVersion SETS "6.33"
+Module_HelpVersion SETS "6.33 (12 Feb 2020)"
END
diff --git a/VersionNum b/VersionNum
index de1a61d7cd9a07ab0ec330671fb19186ec42ec8c..1f9a95d8e68adc91e49f00a9fb9a4a874f7b366f 100644
--- a/VersionNum
+++ b/VersionNum
@@ -1,21 +1,21 @@
-/* (6.32)
+/* (6.33)
*
* This file is automatically maintained by srccommit, do not edit manually.
*
*/
-#define Module_MajorVersion_CMHG 6.32
+#define Module_MajorVersion_CMHG 6.33
#define Module_MinorVersion_CMHG
-#define Module_Date_CMHG 19 Jan 2020
+#define Module_Date_CMHG 12 Feb 2020
-#define Module_MajorVersion "6.32"
-#define Module_Version 632
+#define Module_MajorVersion "6.33"
+#define Module_Version 633
#define Module_MinorVersion ""
-#define Module_Date "19 Jan 2020"
+#define Module_Date "12 Feb 2020"
-#define Module_ApplicationDate "19-Jan-20"
+#define Module_ApplicationDate "12-Feb-20"
#define Module_ComponentName "Kernel"
-#define Module_FullVersion "6.32"
-#define Module_HelpVersion "6.32 (19 Jan 2020)"
-#define Module_LibraryVersionInfo "6:32"
+#define Module_FullVersion "6.33"
+#define Module_HelpVersion "6.33 (12 Feb 2020)"
+#define Module_LibraryVersionInfo "6:33"
diff --git a/hdr/KernelWS b/hdr/KernelWS
index 1b39fa468aec8f511130abf7713e2c12bc2827a4..9b4647bc6d4e9e532c26cc6d3df2836a97142e41 100644
--- a/hdr/KernelWS
+++ b/hdr/KernelWS
@@ -804,6 +804,7 @@ ScreenBlankDPMSState # 1 ; 0 => just blank video
; 1 => blank to stand-by (hsync off)
; 2 => blank to suspend (vsync off)
; 3 => blank to off (H+V off)
+ ; 255 => no mode programmed yet
ASSERT ScreenBlankDPMSState = Legacy_ScreenBlankDPMSState
ASSERT ?ScreenBlankDPMSState = ?Legacy_ScreenBlankDPMSState
diff --git a/s/PMF/osbyte b/s/PMF/osbyte
index 5c7606bda02a24ec41a1354687b5a830be298967..a017b476cfac30286401272dc17f27242a775146 100644
--- a/s/PMF/osbyte
+++ b/s/PMF/osbyte
@@ -563,9 +563,11 @@ Osbyte13 ROUT
TSTNE R1, #3 ; NE => blanked and DPMS turned off HSync or VSync
MyOsbyte NE ; if true exit immediately
- ; Also, exit now if we don't have a driver active
+ ; Also, exit now if we don't have a driver active, or there's no
+ ; mode programmed
LDR R0, [LR,#CurrentGraphicsVDriver]
CMP R0, #GraphicsVInvalid
+ CMPEQ R1, #255
MyOsbyte EQ
; It is actually better to call Idle with interrupts disabled as it stops the interrupt
diff --git a/s/vdu/vdudriver b/s/vdu/vdudriver
index fb0227228bc163a3391f72d7da05b87a5267f769..4f4196c6d2f3265223213d1c3e7bf8ac9c1e7983 100644
--- a/s/vdu/vdudriver
+++ b/s/vdu/vdudriver
@@ -106,9 +106,9 @@ VduInit ROUT
ASSERT (ZeroPage :AND: 255) = 0
STRB R0, [R0, #OsbyteVars + :INDEX: VDUqueueItems] ;purge queue
STRB R0, [WsPtr, #ScreenBlankFlag] ; not blanked
- [ ZeroPage <> 0
+ MOV R0, #255
+ STRB R0, [WsPtr, #ScreenBlankDPMSState] ; however, no mode programmed yet
MOV R0, #0
- ]
STR R0, [WsPtr, #CursorCounter]
STR R0, [WsPtr, #CursorDesiredState]
STR R0, [WsPtr, #VduStatus]
diff --git a/s/vdu/vdupalxx b/s/vdu/vdupalxx
index b31d9a8867a0d6636edc76fc5450b43fe8d462a4..77a104de23ff31f22084e73601006f3ee9cf5725 100644
--- a/s/vdu/vdupalxx
+++ b/s/vdu/vdupalxx
@@ -1064,6 +1064,7 @@ PV_BlankScreen ROUT
AND r0, r0, #1
STRB r0, [WsPtr, #ScreenBlankFlag] ; update new state
LDRB r1, [WsPtr, #ScreenBlankDPMSState]
+ AND r1, r1, #3
LDR r4, [WsPtr, #CurrentGraphicsVDriver]
MOV r4, r4, LSL #24
diff --git a/s/vdu/vduswis b/s/vdu/vduswis
index 0f08566d2a97a8b712568616dad83161d1d9e2ea..25b06b42d32ba39359a76bcea238c4dfca764ec1 100644
--- a/s/vdu/vduswis
+++ b/s/vdu/vduswis
@@ -1273,6 +1273,10 @@ RemovePages ROUT
; display starts in pages that remain
+ CMP R4, #0 ; if we've somehow shrunk to zero,
+ MOVEQ R5, R14 ; then DisplayStart = ScreenEndAddr,
+ BEQ %FT06 ; and avoid the infinite loop below!
+
SUB R5, R3, R0 ; new DisplayStart
05
@@ -1280,6 +1284,7 @@ RemovePages ROUT
SUBCS R5, R5, R4 ; then repeatedly subtract off new size
BCS %BT05 ; until in range
+06
Push "R0-R2"
MOV R0, R5 ; put new display start in r0
BL SetVinit ; this updates DisplayStart
@@ -1302,10 +1307,15 @@ InsertRemovePagesExit
LDR R4, [WsPtr, #DisplayScreenStart]
SUB R0, R4, R0
LDR R3, [WsPtr, #TotalScreenSize]
+
+ CMP R3, #0
+ MOVEQ R0, R14
+ BEQ %FT26
25
CMP R0, R14 ; ensure displayscreenstart in range too
SUBCS R0, R0, R3
BCS %BT25
+26
BL NewScreenStart
30
BL SetVendDefault
@@ -2063,6 +2073,10 @@ ScreenMode_SelectDevice ROUT
MOV r1, #Service_DisplayChanged
MOV r3, #DisplayChangedSub_ModeChanged
IssueService
+ ; Flag that VSync probably isn't working
+ ; (will be cleared by HardwareModeChange)
+ MOV r0, #255
+ STRB r0, [WsPtr, #ScreenBlankDPMSState]
; Update current driver VDU var
STR r2, [WsPtr, #CurrentGraphicsVDriver]
; Issue service call to indicate change is coming
@@ -2071,28 +2085,47 @@ ScreenMode_SelectDevice ROUT
; Call InitialiseMode to select a mode to use for this new driver
CMP r2, #GraphicsVInvalid
BLNE InitialiseMode
- BVS %FT15
- ; Success!
- MOV r0, #DisplayChanged_Changed
- IssueService
- MOV r1, r5
- EXIT
-15
- ; Something went wrong trying to activate the new driver
- ; Try and restore the old one
+ BVC %FT15
+ ; Something went wrong trying to activate the new driver.
+ ; Make sure the VSync flag is still set.
+ MOV lr, #255
+ STRB lr, [WsPtr, #ScreenBlankDPMSState]
+ ; Do we have an old driver we can try and switch back to?
+ ;
+ ; If we don't have an old driver, just stick with this new
+ ; one, under the assumption that the failure was because we
+ ; couldn't find a valid mode to switch to (which is generally
+ ; the only way in which InitialiseMode will fail). For such a
+ ; situation, there's a reasonable chance that things will start
+ ; working later on during the boot sequence, e.g. once an MDF
+ ; is loaded. And for such a case, temporarily having a broken
+ ; driver active is much better than restoring the "no driver"
+ ; state, since we currently don't have any kind of watchdog which
+ ; will kick the video system into life once the MDF does get
+ ; loaded.
+ CMP r5, #GraphicsVInvalid
+ BEQ %FT15
STR r0, [sp] ; Return the error to the caller
STR r5, [WsPtr, #CurrentGraphicsVDriver]
MOV r0, #DisplayChanged_Changing
MOV r2, r5
IssueService
- CMP r5, #GraphicsVInvalid
- BLNE InitialiseMode
+ BL InitialiseMode
+ MOVVS lr, #255
+ STRVSB lr, [WsPtr, #ScreenBlankDPMSState]
; TODO - Try harder if this 2nd call fails (e.g. try all drivers in turn)
MOV r0, #DisplayChanged_Changed
IssueService
MOV r1, r5
SETV
EXIT
+
+15
+ ; Success!
+ MOV r0, #DisplayChanged_Changed
+ IssueService
+ MOV r1, r5
+ EXIT
20
PullEnv
ADR r0, ErrorBlock_BadGDriver