[PATCH 4/5] drm/intel/dp: Try harder to get bpc of a DP sink if EDID doesn't tell.

[Daniel Vetter]

On Wed, Aug 03, 2016 at 01:07:12PM +1000, Dave Airlie wrote:
> On 6 July 2016 at 20:05, Mario Kleiner <mario.kleiner.de at gmail.com> wrote:
> > For DP sinks which don't expose color depth via EDID, use
> > the drm_dp_sink_bpc() helper to derive the bpc of the sink.
> >
> > This should handle DP native sinks with the "Assume 6 bpc if EDID
> > doesn't tell us" as mandated by DP spec. It gives more accurate
> > values for DP->legacy converters for HDMI, DVI and VGA.
> 
> Haswell says no.

Yup indeed, sorry for missing that. Tomeu and Mika Kahola are working on
some fancy new dp helper to probe all that, and as part of that suitably
fill out connector->display_info, too. That would allow both the
inversion, and the dpcd transaction from within atomic_check (which is
kinda not that cool either).
-Daniel

> 
> ug 03 12:58:46 tyrion-bne-redhat-com kernel: fbcon: inteldrmfb (fb0)
> is primary device
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: BUG: unable to handle
> kernel NULL pointer dereference at 000000000000011b
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: IP: [<ffffffffa00e6cf5>]
> drm_dp_sink_bpc+0x5/0xb0 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: PGD 0
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: Oops: 0000 [#1] SMP
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: Modules linked in: i915
> ccm xt_CHECKSUM ipt_MASQUERADE nf_nat_masquerade_ipv4 tun
> ip6t_rpfilter ip6t_
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  videobuf2_core
> snd_hda_codec videodev mei_me mei snd_hwdep snd_seq snd_hda_core
> rtsx_pci media i2c_i
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: CPU: 1 PID: 752 Comm:
> kworker/1:3 Not tainted 4.7.0+ #12
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: Hardware name: LENOVO
> 20ARS25701/20ARS25701, BIOS GJET72WW (2.22 ) 02/21/2014
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: Workqueue: events_long
> drm_dp_mst_link_probe_work [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: task: ffff880308583a80
> task.stack: ffff880309f20000
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: RIP:
> 0010:[<ffffffffa00e6cf5>]  [<ffffffffa00e6cf5>]
> drm_dp_sink_bpc+0x5/0xb0 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: RSP:
> 0018:ffff880309f23b48  EFLAGS: 00010202
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: RAX: 000000000000000a
> RBX: 0000000000000006 RCX: 0000000000000000
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: RDX: 0000000000000000
> RSI: 0000000000000127 RDI: 0000000000000116
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: RBP: ffff880309f23b50
> R08: ffff880309734800 R09: 0000000000000024
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: R10: 0000000000000000
> R11: 0000000000000000 R12: ffff880309737800
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: R13: ffff88030a334000
> R14: ffff880309737000 R15: ffff880309737800
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: FS:
> 0000000000000000(0000) GS:ffff88031e240000(0000)
> knlGS:0000000000000000
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: CS:  0010 DS: 0000 ES:
> 0000 CR0: 0000000080050033
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: CR2: 000000000000011b
> CR3: 0000000001c06000 CR4: 00000000001406e0
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: Stack:
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  ffffffffa09d4295
> ffff880309f23bd8 ffffffffa09a7c1f ffffffff8122544d
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  ffff880306660258
> ffff880306660000 0000000009737800 ffff88030a331000
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  0100880300000024
> ffff880309f23bb8 ffffffff00000024 ffff880309737800
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: Call Trace:
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa09d4295>] ?
> intel_dp_sink_bpc+0x25/0x30 [i915]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa09a7c1f>]
> intel_atomic_check+0xacf/0x1250 [i915]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff8122544d>] ?
> __kmalloc_track_caller+0x12d/0x210
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa0097ea7>]
> drm_atomic_check_only+0x187/0x610 [drm]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa0098857>] ?
> drm_atomic_add_affected_connectors+0x27/0xf0 [drm]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa0098347>]
> drm_atomic_commit+0x17/0x60 [drm]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa00f4e0c>]
> restore_fbdev_mode+0x14c/0x260 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa00f6a23>]
> drm_fb_helper_restore_fbdev_mode_unlocked+0x33/0x80 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa00f6a9d>]
> drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa00f69b8>]
> drm_fb_helper_hotplug_event+0x148/0x180 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa09c238a>]
> intel_fbdev_output_poll_changed+0x1a/0x20 [i915]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa00e79c7>]
> drm_kms_helper_hotplug_event+0x27/0x30 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa09cafa5>]
> intel_dp_mst_hotplug+0x15/0x20 [i915]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa00ee31a>]
> drm_dp_send_link_address+0x19a/0x220 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff810df553>] ?
> put_prev_entity+0x33/0x410
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff8111280b>] ?
> add_timer_on+0xdb/0x1b0
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff8102c766>] ?
> __switch_to+0x2b6/0x600
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff810e361e>] ?
> pick_next_task_fair+0x10e/0x4d0
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa00ee44d>]
> drm_dp_check_and_send_link_address+0xad/0xc0 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffffa00ee4b7>]
> drm_dp_mst_link_probe_work+0x57/0xb0 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff810c086f>]
> process_one_work+0x15f/0x410
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff810c0b6e>]
> worker_thread+0x4e/0x480
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff810c0b20>] ?
> process_one_work+0x410/0x410
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff810c0b20>] ?
> process_one_work+0x410/0x410
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff810c64c8>]
> kthread+0xd8/0xf0
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff817d527f>]
> ret_from_fork+0x1f/0x40
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  [<ffffffff810c63f0>] ?
> kthread_worker_fn+0x170/0x170
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: Code: b8 b0 1e 04 00 48
> 89 e5 74 11 40 80 ff 14 ba d0 78 02 00 b8 60 3d 08 00 0f 45 c2 5d c3
> 66 0f 1f
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: RIP
> [<ffffffffa00e6cf5>] drm_dp_sink_bpc+0x5/0xb0 [drm_kms_helper]
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel:  RSP <ffff880309f23b48>
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: CR2: 000000000000011b
> Aug 03 12:58:46 tyrion-bne-redhat-com kernel: ---[ end trace
> d3270996301ba013 ]---
> 
> Possibly MST related.
> 
> Dave.

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch