[BUG, BISECTED] HDMI not working with Intel Arc GPU

[Harry Yoo <harry.yoo@oracle.com>]

Hi folks, I use my laptop with a second monitor connected via HDMI.
After kernel upgrade, my second monitor became blank (black screen) and
displays nothing. So I started bisection.

Here's my GPU info, the first bad commit, and the git bisect log.
I'm really looking forward to seeing this fixed :-)
I really enjoy working with a second monitor.

$ sudo lshw -C display
  *-display                 
       description: VGA compatible controller
       product: Meteor Lake-P [Intel Arc Graphics]
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       logical name: /dev/fb0
       version: 08
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom fb
       configuration: depth=32 driver=i915 latency=0 mode=1920x1200 resolution=1920,1200 visual=truecolor xres=1920 yres=1200
       resources: iomemory:500-4ff iomemory:400-3ff irq:234 memory:5018000000-5018ffffff memory:4000000000-400fffffff memory:c0000-dffff memory:501a000000-5020ffffff

1efd5384277eb71fce20922579061cd3acdb07cf is the first bad commit
commit 1efd5384277eb71fce20922579061cd3acdb07cf
Author: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Date:   Mon Jan 20 09:51:21 2025 +0530

    drm/i915/cx0_phy: Use HDMI PLL algorithm for C10 PHY
    
    Try HDMI PLL alogorithm for C10 PHY, if there are no pre-computed tables.
    Also get rid of the helpers to get rate for HDMI for C10/20 PHY, as we no
    longer depend only on pre-computed tables.
    
    Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
    Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
    Acked-by: Jani Nikula <jani.nikula@intel.com>
    Tested-by: Khaled Almahallawy <khaled.almahallawy@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20250120042122.1029481-6-ankit.k.nautiyal@intel.com

 drivers/gpu/drm/i915/display/intel_cx0_phy.c | 49 +++++++---------------------
 drivers/gpu/drm/i915/display/intel_cx0_phy.h |  1 -
 drivers/gpu/drm/i915/display/intel_hdmi.c    | 10 ------
 3 files changed, 11 insertions(+), 49 deletions(-)

$ git bisect log
git bisect start
# status: waiting for both good and bad commits
# bad: [0af2f6be1b4281385b618cb86ad946eded089ac8] Linux 6.15-rc1
git bisect bad 0af2f6be1b4281385b618cb86ad946eded089ac8
# status: waiting for good commit(s), bad commit known
# good: [38fec10eb60d687e30c8c6b5420d86e8149f7557] Linux 6.14
git bisect good 38fec10eb60d687e30c8c6b5420d86e8149f7557
# good: [fd71def6d9abc5ae362fb9995d46049b7b0ed391] Merge tag 'for-6.15-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
git bisect good fd71def6d9abc5ae362fb9995d46049b7b0ed391
# bad: [93d52288679e29aaa44a6f12d5a02e8a90e742c5] Merge tag 'backlight-next-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/backlight
git bisect bad 93d52288679e29aaa44a6f12d5a02e8a90e742c5
# bad: [93d52288679e29aaa44a6f12d5a02e8a90e742c5] Merge tag 'backlight-next-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/backlight
git bisect bad 93d52288679e29aaa44a6f12d5a02e8a90e742c5
# bad: [0f04462874e1228cf58e19a3d1710db9757dd695] Merge tag 'drm-misc-next-fixes-2025-03-13' of https://gitlab.freedesktop.org/drm/misc/kernel into drm-next
git bisect bad 0f04462874e1228cf58e19a3d1710db9757dd695
# bad: [0f04462874e1228cf58e19a3d1710db9757dd695] Merge tag 'drm-misc-next-fixes-2025-03-13' of https://gitlab.freedesktop.org/drm/misc/kernel into drm-next
git bisect bad 0f04462874e1228cf58e19a3d1710db9757dd695
# good: [80e54e84911a923c40d7bee33a34c1b4be148d7a] Linux 6.14-rc6
git bisect good 80e54e84911a923c40d7bee33a34c1b4be148d7a
# good: [80e54e84911a923c40d7bee33a34c1b4be148d7a] Linux 6.14-rc6
git bisect good 80e54e84911a923c40d7bee33a34c1b4be148d7a
# bad: [16893dd23f6d1e3a4dd6da272ef9960825da3ebd] Merge tag 'drm-intel-next-2025-02-24' of https://gitlab.freedesktop.org/drm/i915/kernel into drm-next
git bisect bad 16893dd23f6d1e3a4dd6da272ef9960825da3ebd
# good: [fb51bf02551958265b7116f6ba92752295c83c26] Merge tag 'v6.14-rc4' into drm-next
git bisect good fb51bf02551958265b7116f6ba92752295c83c26
# bad: [778be378be2a0e0528dd1ea44ed3dc9804950fc3] drm/i915: Move icl+ nv12 plane register mangling into skl_universal_plane.c
git bisect bad 778be378be2a0e0528dd1ea44ed3dc9804950fc3
# bad: [99f4cb4fb222b42703b43551d55c9ec2520d9d5b] drm/i915/dp: Pass .4 BPP values to {icl,xelpd}_dsc_compute_link_config()
git bisect bad 99f4cb4fb222b42703b43551d55c9ec2520d9d5b
# good: [68f3a505b367656a2db05406a62dc43fb0c50034] drm/i915/psr: Enable Panel Replay on sink always when it's supported
git bisect good 68f3a505b367656a2db05406a62dc43fb0c50034
# bad: [381ab12d483ea30af4ca52db51d23c947f2904c1] drm/i915: fix typos in drm/i915 files
git bisect bad 381ab12d483ea30af4ca52db51d23c947f2904c1
# good: [d49b485d1be3cb1b3b719cf4031f879dbc26c633] drm/i915/dp_mst: Use intel_connector vs. drm_connector pointer in intel_dp_mst.c
git bisect good d49b485d1be3cb1b3b719cf4031f879dbc26c633
# bad: [1efd5384277eb71fce20922579061cd3acdb07cf] drm/i915/cx0_phy: Use HDMI PLL algorithm for C10 PHY
git bisect bad 1efd5384277eb71fce20922579061cd3acdb07cf
# good: [5947642004bfd56436ce63d3e65d517b5be52549] drm/i915/display: Add support for SNPS PHY HDMI PLL algorithm for DG2
git bisect good 5947642004bfd56436ce63d3e65d517b5be52549
# good: [18176f56942a596c5d03ed69ef30ad72f67a7edc] drm/i915/cx0_phy_regs: Add C10 registers bits
git bisect good 18176f56942a596c5d03ed69ef30ad72f67a7edc
# good: [82ecaae2360776dcd0b9abf9ae6b947c28025931] drm/i915/intel_snps_hdmi_pll: Compute C10 HDMI PLLs with algorithm
git bisect good 82ecaae2360776dcd0b9abf9ae6b947c28025931
# first bad commit: [1efd5384277eb71fce20922579061cd3acdb07cf] drm/i915/cx0_phy: Use HDMI PLL algorithm for C10 PHY

-- 
Cheers,
Harry / Hyeonggon