Re: kern/55198: When the video card is Intel Mobile 965GM Express,i915drmkmshas error CPU pipe A FIFO underrun, also X freezes/hangs

[Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>]

>  > So I think the easiest fix would make "uxa" the default acceleration method on old chips as Intel 965GM.
>  
>  Mine is N455 GMA 3150.  Maybe all GMA Intel GPUs are affected?
>   https://en.wikipedia.org/wiki/Intel_GMA#Generation_three_based

The attachend diff makes old (Gen4 and prior) chipsets use UXA
by default. Is it worth to apply netbsd-9 for workaround?

---
Index: external/mit/xf86-video-intel/dist/src/intel_module.c
===================================================================
RCS file: /cvsroot/xsrc/external/mit/xf86-video-intel/dist/src/intel_module.c,v
retrieving revision 1.1.1.4
diff -u -p -d -r1.1.1.4 intel_module.c
--- external/mit/xf86-video-intel/dist/src/intel_module.c	20 Mar 2019 06:34:02 -0000	1.1.1.4
+++ external/mit/xf86-video-intel/dist/src/intel_module.c	8 May 2020 15:05:46 -0000
@@ -567,9 +567,8 @@ _xf86findDriver(const char *ident, XF86C
 	return NULL;
 }
 
-static enum accel_method { NOACCEL, SNA, UXA } get_accel_method(void)
+static enum accel_method { NOACCEL, SNA, UXA } get_accel_method(enum accel_method accel_method)
 {
-	enum accel_method accel_method = DEFAULT_ACCEL_METHOD;
 	XF86ConfDevicePtr dev;
 
 	if (hosted())
@@ -641,7 +640,12 @@ intel_scrn_create(DriverPtr		driver,
 #endif
 
 #if KMS
-	switch (get_accel_method()) {
+	enum accel_method default_accel_method = DEFAULT_ACCEL_METHOD;
+	/* Force UXA by default for pre-HD chipset to avoid screen corruption */
+	if ((unsigned)((struct intel_device_info *)match_data)->gen < 050)
+		default_accel_method = UXA;
+
+	switch (get_accel_method(default_accel_method)) {
 #if USE_SNA
 	case NOACCEL:
 	case SNA:

---
Izumi Tsutsui