On Thu, May 16, 2013 at 9:24 AM, Ben Guthro <ben at guthro.net> wrote: > On Wed, May 15, 2013 at 4:42 PM, Ben Guthro <ben at guthro.net> wrote: >> On Tue, May 14, 2013 at 5:01 PM, Ben Guthro <ben at guthro.net> wrote: >>> I am attempting to debug an issue with some Haswell laptop systems >>> which do not restore their screen after resuming from S3 when running >>> on the stable 3.8 kernel (3.8.13) >>> The backlight is OK, but the screen is just black. >>> >>> In trying to determine what was going wrong, I tried looking at the >>> output of intel_reg_dumper, in a good, and bad case: >>> >>> diff -u good_reg.txt bad_reg.txt >>> --- good_reg.txt 2013-05-14 15:08:44.361997000 +0000 >>> +++ bad_reg.txt 2013-05-14 15:09:20.480000000 +0000 >>> @@ -1,5 +1,4 @@ >>> - DCC: 0x00000000 (0x00000000f3400000 >>> 0x00000000f37fffff 0x00000000?? >>> -? ) >>> + DCC: 0x00000000 (0x00000000f3400000 >>> 0x00000000f37fffff 0x00000000??= ? ) >>> CHDECMISC: 0x00000000 (none, ch2 enh disabled, ch1 enh >>> disabled, ch0 enh disabled, flex disabled, ep not present) >>> C0DRB0: 0x00000000 (0x0000) >>> C0DRB1: 0x00000000 (0x0000) >>> @@ -63,17 +62,17 @@ >>> PIPEA_DP_LINK_N: 0x00000000 >>> CURSOR_A_BASE: 0x01061000 >>> CURSOR_A_CONTROL: 0x04000027 >>> - CURSOR_A_POSITION: 0x03a3032f >>> + CURSOR_A_POSITION: 0x01bb03fb >>> FPA0: 0x00000000 (n = 0, m1 = 0, m2 = 0) >>> FPA1: 0x00000000 (n = 0, m1 = 0, m2 = 0) >>> DPLL_A: 0x00000000 (disabled, non-dvo, VGA, default >>> clock, unknown mode, p1 = 0, p2 = 0) >>> DPLL_A_MD: 0x00000000 >>> - HTOTAL_A: 0x0821077f (1920 active, 2082 total) >>> - HBLANK_A: 0x0821077f (1920 start, 2082 end) >>> - HSYNC_A: 0x081307af (1968 start, 2068 end) >>> - VTOTAL_A: 0x045f0437 (1080 active, 1120 total) >>> - VBLANK_A: 0x045f0437 (1080 start, 1120 end) >>> - VSYNC_A: 0x044b0441 (1090 start, 1100 end) >>> + HTOTAL_A: 0x00000000 (1 active, 1 total) >>> + HBLANK_A: 0x00000000 (1 start, 1 end) >>> + HSYNC_A: 0x00000000 (1 start, 1 end) >>> + VTOTAL_A: 0x00000000 (1 active, 1 total) >>> + VBLANK_A: 0x00000000 (1 start, 1 end) >>> + VSYNC_A: 0x00000000 (1 start, 1 end) >>> BCLRPAT_A: 0x00000000 >>> VSYNCSHIFT_A: 0x00000000 >>> DSPBCNTR: 0x00004000 (disabled, pipe A) >>> >>> >>> It appears the registers that are saved, and restored in >>> i915_save_modeset_reg / i915_restore_modeset_reg is not working >>> properly. >>> >>> When I put some debug in, I discovered that it was bailing out of >>> i915_save_modeset_reg early since the DRIVER_MODESET bit was cleared. >>> However, it was set at the end of i915_init() >>> This, of course, confuses me. >>> >>> Am I seeing memory corruption here? >> >> It looks like I misread the code here, inversing an if statement state. >> >> That said, I don't really have any clues as to why the display is >> black after resuming from S3 It appears that S3 is not necessary. I can reproduce the black screen with just vbetool: vbetool dpms off vbetool dpms on Does this suggest a bios issue? >> >> Is this an eDP training issue? Are there any changesets I can try backporting? >> I tried this, but it didn't seem to help: >> https://patchwork.kernel.org/patch/2516601/ > > > Below is a serial dump with drm.debug=4, after resuming from S3 > > If anyone sees anything awry, being pointed in the right direction > would be appreciated: