Regression related to DSC on JSL Chromebook
We've encountered some regressions (IGT failures, blank screen) on a JSL based Chromebook with a particular panel. After debugging and bisecting, we've found that the regressions start occurring from 265bb1cbe3d69 drm/i915/vdsc: Add function to write in PPS register.
The change in question looks like it's supposed to be a no-op, but I dumped out the register/value being written to from within intel_dsc_pps_configure, and found that the register for PPS 16 was (inadvertently?) changed with the refactor.
Before the change, the register written to for PPS16 is defined as:
#define DSCA_PICTURE_PARAMETER_SET_16 _MMIO(0x6B270)After the change, the register written to for PPS16 is calculated through DSCA_PPS(16) to 0x0006b240 per:
#define DSCA_PPS(pps) _MMIO(_DSCA_PPS_0 + (pps) * 4)
#define _DSCA_PPS_0 0x6B200The previous value of 0x6B270 corresponds to DSCA_PPS(0x1c) so I tried changing the relevant calls to intel_dsc_write_pps_reg and intel_dsc_read_and_verify_pps_reg to use 0x1c instead of 16, and the tests passed and related drm error logs went away as well.
Is it expected for that change to affect the address of the PPS 16 register?
A few other notes that may be relevant:
- We have multiple JSL Chromebooks, but AFAICT this is the only one that was regressed by this change
- the affected chromebook has a MIPI display
- I haven't been able to run any tests on latest upstream stable due to a bootloop from an unrelated failure, but after booting the device survives long enough that I can verify that related DRM error logs go away after I make the
0x1cchange as referenced above.
Example error message that is correlated to the test failures and display regressions:
[ 4.904064] i915 0000:00:02.0: [drm] *ERROR* [CRTC:98:pipe A] mismatch in dsc.config.slice_chunk_size (expected 1600, found 2176)
[ 4.904074] ------------[ cut here ]------------
[ 4.904076] pipe state doesn't match!
[ 4.904092] WARNING: CPU: 0 PID: 433 at drivers/gpu/drm/i915/display/intel_modeset_verify.c:220 intel_modeset_verify_crtc+0x375/0x3a7
[ 4.904098] Modules linked in: btusb btrtl btintel btmtk btbcm bluetooth ecdh_generic ecc joydev
[ 4.904109] CPU: 0 PID: 433 Comm: frecon Tainted: G U 6.1.74-09529-g9c60ae9d8d01 #1 0454e17af5796fb0926aa5fbcc19b8f2d17c56be
[ 4.904114] Hardware name: Google Bugzzy/Bugzzy, BIOS Google_Bugzzy.13606.533.3 03/21/2023
[ 4.904116] RIP: 0010:intel_modeset_verify_crtc+0x375/0x3a7
[ 4.904121] Code: 8b 11 48 c7 c7 ba 5f d1 b3 48 89 c6 44 89 f1 45 89 e0 e8 51 44 97 ff 0f 0b e9 f4 fe ff ff 48 c7 c7 1e d7 c8 b3 e8 3e 44 97 ff <0f> 0b e9 0b ff ff ff e8 f8 85 57 00 48 c7 c7 ca 71 c9 b3 e8 26 44
[ 4.904124] RSP: 0018:ffff9c9bc198fa50 EFLAGS: 00010246
[ 4.904127] RAX: 3b5ddee7a1883900 RBX: ffff9b888c5dc000 RCX: ffffffffb4460108
[ 4.904129] RDX: 0000000000000000 RSI: 00000000ffffdfff RDI: 0000000000000001
[ 4.904132] RBP: ffff9c9bc198fab0 R08: 0000000000000000 R09: ffff9c9bc198f8b0
[ 4.904134] R10: 00000000ffffdfff R11: ffffffffb44903b0 R12: ffff9b8881b2e000
[ 4.904137] R13: 0000000000000001 R14: ffff9b8881abf000 R15: ffff9b8881ac8000
[ 4.904139] FS: 00007888431bb740(0000) GS:ffff9b88fc000000(0000) knlGS:0000000000000000
[ 4.904142] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4.904145] CR2: 00005b10321389e8 CR3: 0000000105860000 CR4: 0000000000350ef0
[ 4.904147] Call Trace:
[ 4.904151] <TASK>
[ 4.904155] ? __warn+0xa4/0x155
[ 4.904159] ? intel_modeset_verify_crtc+0x375/0x3a7
[ 4.904162] ? report_bug+0xd5/0x16a
[ 4.904168] ? handle_bug+0x41/0x67
[ 4.904171] ? exc_invalid_op+0x1b/0x4c
[ 4.904174] ? asm_exc_invalid_op+0x16/0x20
[ 4.904178] ? intel_modeset_verify_crtc+0x375/0x3a7
[ 4.904182] intel_atomic_commit_tail+0xd5e/0xedf
[ 4.904187] ? wake_bit_function+0x31/0x31
[ 4.904190] ? wake_bit_function+0x31/0x31
[ 4.904194] intel_atomic_commit+0x312/0x354
[ 4.904197] drm_atomic_commit+0xe8/0x10d
[ 4.904202] ? __drm_printfn_debug_syslog+0x1d/0x1d
[ 4.904205] drm_mode_atomic_ioctl+0x35e/0x482
[ 4.904210] ? drm_atomic_set_property+0x986/0x986
[ 4.904214] drm_ioctl_kernel+0xdd/0x153
[ 4.904218] drm_ioctl+0x29f/0x422
[ 4.904221] ? drm_atomic_set_property+0x986/0x986
[ 4.904225] __se_sys_ioctl+0x78/0xbc
[ 4.904230] do_syscall_64+0x4e/0x9b
[ 4.904234] ? exit_to_user_mode_prepare+0x6c/0x85
[ 4.904237] entry_SYSCALL_64_after_hwframe+0x5e/0xc8
[ 4.904241] RIP: 0033:0x788843371029
[ 4.904245] Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10 c7 45 b0 10 00 00 00 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00 00 0f 05 <41> 89 c0 3d 00 f0 ff ff 77 1d 48 8b 45 c8 64 48 2b 04 25 28 00 00
[ 4.904248] RSP: 002b:00007fff6df64250 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[ 4.904251] RAX: ffffffffffffffda RBX: 00007fff6df64310 RCX: 0000788843371029
[ 4.904254] RDX: 00007fff6df64310 RSI: 00000000c03864bc RDI: 0000000000000007
[ 4.904256] RBP: 00007fff6df642a0 R08: 0000000000000104 R09: 000059efdb2d1f40
[ 4.904258] R10: 0000000000000000 R11: 0000000000000246 R12: 000059efdb47bbc0
[ 4.904260] R13: 0000000000000000 R14: 00000000c03864bc R15: 0000000000000007
[ 4.904263] </TASK>
[ 4.904265] ---[ end trace 0000000000000000 ]---