radeontool: Avoid lockup on ‘radeontool regmatch '*'’ on r128

Running ‘radeontool regmatch '*'’ with an ATI Rage 128 Mobility M3 LF
(AGP) locks up the system.

The register reads that lock up are CRTC2_CRNT_FRAME and
CRTC2_VLINE_CRNT_VLINE; it is not clear to me why.  From the
xf86-video-r128 source I can see that this is one of the handful of
r128 chips that supports dual-head operation, but at the time of the
lockup, the CRTC2_GEN_CNTL register had value 0x0 (i.e., CRTC2
disabled); maybe that’s why.

Presumably these two registers would only be relevant if CRTC2 is
enabled, so as a safety measure, check for that before displaying them
with ‘radeontool regmatch [pattern]’.

A similar crash was reported on 2009-12-02 on #radeon for an R300, so
presumably this problem is not restricted to pre-Radeon cards.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/radeontool.c b/radeontool.c
index d4968e5..520a8af 100644
--- a/radeontool.c
+++ b/radeontool.c
@@ -732,11 +732,23 @@ void radeon_reg_match(const char *pattern)
         printf("%s\t0x%08x (%d)\n", pattern, value, value);
     }
     else {
+        int crtc2_enabled;
+
         /* Prepare for a crash (just in case). */
         sync();
 
+        /* dual-head setup? */
+        value = radeon_get(RADEON_CRTC2_GEN_CNTL, "RADEON_CRTC2_GEN_CTRL");
+        crtc2_enabled = (value & RADEON_CRTC2_EN) ? 1 : 0;
+
         for (i = 0; i < sizeof(reg_list) / sizeof(reg_list[0]); i++) {
             if (fnmatch(pattern, reg_list[i].name, 0) == 0) {
+                if (!crtc2_enabled &&
+                    (reg_list[i].address == RADEON_CRTC2_CRNT_FRAME ||
+                     reg_list[i].address == RADEON_CRTC2_VLINE_CRNT_VLINE))
+                    /* might freeze, so skip it */
+                    continue;
+
                 printf("%s (%s%04x)\t", reg_list[i].name,
                        reg_list[i].type, reg_list[i].address);