Re: [PATCH v3 00/43] DRM Rockchip rk3399 (Kevin)

From: Marek Szyprowski
Date: Thu Mar 01 2018 - 08:06:29 EST

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In reply to: Marek Szyprowski: "Re: [PATCH v3 00/43] DRM Rockchip rk3399 (Kevin)"
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Hi All once again,

On 2018-03-01 12:06, Marek Szyprowski wrote:

On 2018-03-01 09:50, Marek Szyprowski wrote:

On 2018-01-30 21:28, Thierry Escande wrote:

This patchset includes cleanups, improvements, and bug fixes for
Rockchip DRM driver and PSR support.

this patchset depends and needs to be applied on top of Rockchip rk3399
eDP support [1].

[1] https://lkml.org/lkml/2018/1/10/682

I've applied this patchset on vanilla v4.16-rc1 and check how it works on
Exynos5250-based Chromeboo Snow and Exynos5420-based Chromebook2 Peach-Pit
boards. Sadly it breaks exynos_dp drm driver.

Here is the log:

[ÂÂÂ 3.540955] [drm] Exynos DRM: using 14400000.fimd device for DMA mapping operations
[ÂÂÂ 3.548810] exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
[ÂÂÂ 3.555350] exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops)
[ÂÂÂ 3.564622] Unable to handle kernel NULL pointer dereference at virtual address 000007d8
[ÂÂÂ 3.571465] pgd = 28ffa2e4
[ÂÂÂ 3.573977] [000007d8] *pgd=00000000
[ÂÂÂ 3.577543] Internal error: Oops: 5 [#1] PREEMPT SMP ARM
[ÂÂÂ 3.582817] Modules linked in:
[ÂÂÂ 3.585846] CPU: 6 PID: 69 Comm: kworker/6:1 Not tainted 4.16.0-rc1-00062-ge25751974ba8 #3622
[ÂÂÂ 3.594369] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[ÂÂÂ 3.600437] Workqueue: events deferred_probe_work_func
[ÂÂÂ 3.605547] PC is at analogix_dp_resume+0x8/0xc0
[ÂÂÂ 3.610144] LR is at pm_generic_runtime_resume+0x2c/0x38
[ÂÂÂ 3.615434] pc : [<c0531b98>]ÂÂÂ lr : [<c0543fec>] psr: a0000113
[ÂÂÂ 3.621684] sp : ee13fbd8Â ip : 0000001aÂ fp : 00000001
[ÂÂÂ 3.626885] r10: ee0eb080Â r9 : c0552bd8Â r8 : c0fb1d98
[ÂÂÂ 3.632090] r7 : eebb1010Â r6 : eeae9808Â r5 : 00000000Â r4 : d4850415
[ÂÂÂ 3.638602] r3 : ee0ed010Â r2 : b2d05e00Â r1 : 00000000Â r0 : 00000000
[ÂÂÂ 3.645109] Flags: NzCvÂ IRQs onÂ FIQs onÂ Mode SVC_32Â ISA ARM Segment none
[ÂÂÂ 3.652224] Control: 10c5387dÂ Table: 2000406aÂ DAC: 00000051
[ÂÂÂ 3.657944] Process kworker/6:1 (pid: 69, stack limit = 0x913205b4)
[ÂÂÂ 3.664192] Stack: (0xee13fbd8 to 0xee140000)
[ÂÂÂ 3.668523] fbc0: d4850415 00000000
[ÂÂÂ 3.676698] fbe0: eeae9808 c0543fec c0543fc0 c054ffb4 00000000 c0552d24 00000001 ee10b400
[ÂÂÂ 3.684852] fc00: c09d1500 eebb1010 eebb10b8 eebad810 00000000 00000004 c0552bd8 00000000
[ÂÂÂ 3.693007] fc20: c016f5c4 c0547798 00000000 eebb1010 c0f05900 eebad810 c0552bd8 00000004
[ÂÂÂ 3.701163] fc40: 00000000 00000000 c016f5c4 c0547898 00000000 eebb1010 c0f05900 c0546ff4
[ÂÂÂ 3.709315] fc60: 60000113 c05475dc 00000001 eebb1010 00000000 c1711b78 eebb10b8 eebb1010
[ÂÂÂ 3.717470] fc80: 00000004 eebb10b8 60000113 eebb1010 00000000 c1711b78 c0f75ce0 c05475ec
[ÂÂÂ 3.725624] fca0: 00000000 ecc59458 ecc5948c c0f75d4c 00000001 c053b95c ecc59458 00000001
[ÂÂÂ 3.733779] fcc0: 00000001 ecc59458 ecc59458 c0f75d4c c0f08448 c053ad08 ecc59458 ecc59460
[ÂÂÂ 3.741934] fce0: 00000000 c05390d0 ecc595a4 c1711c3c c0c7310c ecc61000 000001ff d186fc33
[ÂÂÂ 3.750088] fd00: ecc59458 ecc59398 c1715440 ecc59458 ecc61000 000001ff 00000001 c0fb1738
[ÂÂÂ 3.758242] fd20: 00000000 c06764c4 c0fb1738 c0678130 ecc59010 eebb1010 00000000 ecc61000
[ÂÂÂ 3.766397] fd40: 000001ff c05321c8 00000003 c0c70b70 ecc59010 eebb1010 ee0ed010 eebb1010
[ÂÂÂ 3.774551] fd60: 00000000 00000000 ecc50b7c c0528e90 00000000 c053fa60 ed99b080 00000002
[ÂÂÂ 3.782706] fd80: 00000028 ee0ec340 ecc61000 c0535bc4 00000000 00000000 ffffffff 00000000
[ÂÂÂ 3.790860] fda0: c0f62f80 ee0eb280 ecc61000 c0f63c80 ee031410 eebb0c10 c0fb1738 c0522ee8
[ÂÂÂ 3.799015] fdc0: c0522d8c ee0e82c0 00000050 00000004 ed99b050 ed99b080 c0f6375c c0536378
[ÂÂÂ 3.807169] fde0: 00000001 c0f63710 c0522b70 ee0ec340 ee0ec340 ed99b080 00000000 c0f63754
[ÂÂÂ 3.815324] fe00: ee0ec340 c1711bc0 c0f6333c 00000000 00000007 c05364fc ecc50b7c eebb1000
[ÂÂÂ 3.823479] fe20: ee0ed010 eebb1010 c0f6333c c0528fe4 ee13fe3c 00000000 00000000 ecc50b7c
[ÂÂÂ 3.831633] fe40: 00000000 eebb1010 fffffdfb c053debc c053de6c eebb1010 c1711bbc 00000000
[ÂÂÂ 3.839787] fe60: c0fb19f0 c053bd18 00000001 c053e4d4 c0f6333c 00000000 ee13feb0 c053c054
[ÂÂÂ 3.847942] fe80: 00000001 c0f63bb4 c0fb19f0 c0fc50a0 c1711bbc c0539e4c ee8a3ad4 ed996a54
[ÂÂÂ 3.856096] fea0: eebb1010 eebb1044 c0f63c80 c053b970 eebb1010 00000001 00000001 ee0d4100
[ÂÂÂ 3.864251] fec0: eebb1010 c0f63c80 c0f63b68 c053ad08 ee0d4100 eefa50c0 eebb1010 c053b258
[ÂÂÂ 3.872405] fee0: c053b21c ee0d4100 eefa50c0 ee13ff28 eefa8300 c0f63bd8 00000000 c0fa8ae5
[ÂÂÂ 3.880560] ff00: c0f0846c c014352c 00000001 00000000 c014347c 60000193 c09cb114 eefa50c0
[ÂÂÂ 3.888714] ff20: c0143c38 00000000 c0f63bd8 c110ef34 00000000 c0c71fdc c0f05900 ee0d4100
[ÂÂÂ 3.896869] ff40: eefa50c0 eefa50f4 c0143bfc c0fa9a27 00000008 ee0d4118 c0f05900 c0143b84
[ÂÂÂ 3.905024] ff60: c09d14d4 eeae7280 ee0d5000 eeae7280 ee0d5000 00000000 eeae72b8 ee0d4100
[ÂÂÂ 3.913178] ff80: ee9b5eb0 c0143b50 00000000 c014a30c ee0d5000 c014a1e4 00000000 00000000
[ÂÂÂ 3.921332] ffa0: 00000000 00000000 00000000 c01010b4 00000000 00000000 00000000 00000000
[ÂÂÂ 3.929486] ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ÂÂÂ 3.937641] ffe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
[ÂÂÂ 3.945800] [<c0531b98>] (analogix_dp_resume) from [<c0543fec>] (pm_generic_runtime_resume+0x2c/0x38)
[ÂÂÂ 3.955001] [<c0543fec>] (pm_generic_runtime_resume) from [<c054ffb4>] (__genpd_runtime_resume+0x2c/0x8c)
[ÂÂÂ 3.964543] [<c054ffb4>] (__genpd_runtime_resume) from [<c0552d24>] (genpd_runtime_resume+0x14c/0x258)
[ÂÂÂ 3.973824] [<c0552d24>] (genpd_runtime_resume) from [<c0547798>] (__rpm_callback+0x134/0x214)
[ÂÂÂ 3.982409] [<c0547798>] (__rpm_callback) from [<c0547898>] (rpm_callback+0x20/0x80)
[ÂÂÂ 3.990126] [<c0547898>] (rpm_callback) from [<c0546ff4>] (rpm_resume+0x3a0/0x734)
[ÂÂÂ 3.997672] [<c0546ff4>] (rpm_resume) from [<c05475ec>] (__pm_runtime_resume+0x64/0x9c)
[ÂÂÂ 4.005654] [<c05475ec>] (__pm_runtime_resume) from [<c053b95c>] (__device_attach+0x8c/0x134)
[ÂÂÂ 4.014157] [<c053b95c>] (__device_attach) from [<c053ad08>] (bus_probe_device+0x88/0x90)
[ÂÂÂ 4.022314] [<c053ad08>] (bus_probe_device) from [<c05390d0>] (device_add+0x3a8/0x580)
[ÂÂÂ 4.030209] [<c05390d0>] (device_add) from [<c06764c4>] (i2c_register_adapter+0xd4/0x3ec)
[ÂÂÂ 4.038360] [<c06764c4>] (i2c_register_adapter) from [<c05321c8>] (analogix_dp_bind+0x2a0/0x410)
[ÂÂÂ 4.047128] [<c05321c8>] (analogix_dp_bind) from [<c0528e90>] (exynos_dp_bind+0x9c/0x12c)
[ÂÂÂ 4.055277] [<c0528e90>] (exynos_dp_bind) from [<c0535bc4>] (component_bind_all+0xfc/0x258)
[ÂÂÂ 4.063605] [<c0535bc4>] (component_bind_all) from [<c0522ee8>] (exynos_drm_bind+0x15c/0x28c)
[ÂÂÂ 4.072107] [<c0522ee8>] (exynos_drm_bind) from [<c0536378>] (try_to_bring_up_master+0x1b8/0x29c)
[ÂÂÂ 4.080957] [<c0536378>] (try_to_bring_up_master) from [<c05364fc>] (component_add+0xa0/0x170)
[ÂÂÂ 4.089545] [<c05364fc>] (component_add) from [<c0528fe4>] (exynos_dp_probe+0x64/0xb8)
[ÂÂÂ 4.097437] [<c0528fe4>] (exynos_dp_probe) from [<c053debc>] (platform_drv_probe+0x50/0xb0)
[ÂÂÂ 4.105766] [<c053debc>] (platform_drv_probe) from [<c053bd18>] (driver_probe_device+0x2b8/0x4a0)
[ÂÂÂ 4.114615] [<c053bd18>] (driver_probe_device) from [<c0539e4c>] (bus_for_each_drv+0x44/0x8c)
[ÂÂÂ 4.123115] [<c0539e4c>] (bus_for_each_drv) from [<c053b970>] (__device_attach+0xa0/0x134)
[ÂÂÂ 4.131355] [<c053b970>] (__device_attach) from [<c053ad08>] (bus_probe_device+0x88/0x90)
[ÂÂÂ 4.139509] [<c053ad08>] (bus_probe_device) from [<c053b258>] (deferred_probe_work_func+0x3c/0x168)
[ÂÂÂ 4.148536] [<c053b258>] (deferred_probe_work_func) from [<c014352c>] (process_one_work+0x1d0/0x7bc)
[ÂÂÂ 4.157644] [<c014352c>] (process_one_work) from [<c0143b84>] (worker_thread+0x34/0x4dc)
[ÂÂÂ 4.165710] [<c0143b84>] (worker_thread) from [<c014a30c>] (kthread+0x128/0x164)
[ÂÂÂ 4.173080] [<c014a30c>] (kthread) from [<c01010b4>] (ret_from_fork+0x14/0x20)
[ÂÂÂ 4.180274] Exception stack(0xee13ffb0 to 0xee13fff8)
[ÂÂÂ 4.185295] ffa0: 00000000 00000000 00000000 00000000
[ÂÂÂ 4.193466] ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ÂÂÂ 4.201620] ffe0: 00000000 00000000 00000000 00000000 00000013 00000000
[ÂÂÂ 4.208207] Code: e2800e37 eafee601 e92d4070 e1a05000 (e59067d8)
[ÂÂÂ 4.214370] ---[ end trace bf6046013df7cab2 ]---

This oops happens, because analogix_dp_bind() calls drm_dp_aux_register()
which registers i2c adapter. I2C core tries to runtime get i2c host
device during registration. This ends in analogix_dp_resume(), but dp
context is NULL there. dp context is set in exynos_dp_bind() after
executing analogix_dp_bind().

A quick workaround of this issue is to postpone enabling runtime PM
on analogix device:

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index 8217c106c72b..db5a6b82815d 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1621,8 +1621,6 @@ analogix_dp_bind(struct device *dev, struct drm_device *drm_dev,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return ERR_PTR(-ENODEV);
ÂÂÂÂÂÂÂ }

-ÂÂÂÂÂÂ pm_runtime_enable(dev);
-
ÂÂÂÂÂÂÂ ret = devm_request_threaded_irq(&pdev->dev, dp->irq,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ analogix_dp_hardirq,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ analogix_dp_irq_thread,
@@ -1642,7 +1640,9 @@ analogix_dp_bind(struct device *dev, struct drm_device *drm_dev,

ÂÂÂÂÂÂÂ ret = drm_dp_aux_register(&dp->aux);
ÂÂÂÂÂÂÂ if (ret)
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ goto err_disable_pm_runtime;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return ERR_PTR(ret);
+
+ÂÂÂÂÂÂ pm_runtime_enable(dev);

ÂÂÂÂÂÂÂ ret = analogix_dp_create_bridge(drm_dev, dp);
ÂÂÂÂÂÂÂ if (ret) {

With such patch Exynos based boards boot, but there is significant delay
related to i2c/aux channel timeout:

[ÂÂÂ 3.510610] [drm] Exynos DRM: using 14400000.fimd device for DMA mapping operations
[ÂÂÂ 3.517733] exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
[ÂÂÂ 3.524483] exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops)
[ÂÂÂ 3.533743] exynos-drm exynos-drm: bound 145b0000.dp-controller (ops exynos_dp_ops)
[ÂÂÂ 3.540074] exynos-drm exynos-drm: bound 14530000.hdmi (ops hdmi_component_ops)
[ÂÂÂ 3.547262] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ÂÂÂ 3.553899] [drm] No driver support for vblank timestamp query.
[ÂÂÂ 3.580467] exynos-dp 145b0000.dp-controller: AUX CH cmd reply timeout!
[ÂÂÂ 4.085814] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 4.590904] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 5.095930] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 5.601022] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 6.106031] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 6.611095] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 7.116112] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 7.621150] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 8.126191] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 8.638389] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 9.138537] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 9.638613] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 10.138698] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 10.638784] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 11.138939] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 11.639025] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 12.139186] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 12.639281] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 13.139368] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 13.216585] exynos-dp 145b0000.dp-controller: Link Training Clock Recovery success
[ÂÂ 13.218846] exynos-dp 145b0000.dp-controller: Link Training success!
[ÂÂ 13.333502] Console: switching to colour frame buffer device 170x48
[ÂÂ 13.446186] exynos-drm exynos-drm: fb0:Â frame buffer device
[ÂÂ 13.456751] [drm] Initialized exynos 1.0.0 20110530 for exynos-drm on minor 0

I've added some debugs and they reveal that AUX CH timeouts happen until DP
PHY is powered on:

[ÂÂÂ 3.511022] [drm] Exynos DRM: using 14400000.fimd device for DMA mapping operations
[ÂÂÂ 3.518137] exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
[ÂÂÂ 3.524900] exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops)
[ÂÂÂ 3.533944] exynos-drm exynos-drm: bound 145b0000.dp-controller (ops exynos_dp_ops)
[ÂÂÂ 3.540231] exynos-drm exynos-drm: bound 14530000.hdmi (ops hdmi_component_ops)
[ÂÂÂ 3.547447] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ÂÂÂ 3.554077] [drm] No driver support for vblank timestamp query.
[ÂÂÂ 3.580511] exynos-dp 145b0000.dp-controller: AUX CH cmd reply timeout!
[ÂÂÂ 4.085882] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 4.590979] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 5.095986] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 5.601057] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 6.106110] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 6.611168] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 7.116212] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 7.621290] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 8.126331] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 8.638578] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 9.138715] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂÂ 9.638872] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 10.138963] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 10.639057] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 11.139208] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 11.639374] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 12.139451] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 12.639553] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 13.139636] exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
[ÂÂ 13.211826] analogix_dp_set_bridge line 1270 phy_power_on
[ÂÂ 13.216999] exynos-dp 145b0000.dp-controller: Link Training Clock Recovery success
[ÂÂ 13.219235] exynos-dp 145b0000.dp-controller: Link Training success!
[ÂÂ 13.333802] Console: switching to colour frame buffer device 170x48
[ÂÂ 13.453198] exynos-drm exynos-drm: fb0:Â frame buffer device
[ÂÂ 13.462463] [drm] Initialized exynos 1.0.0 20110530 for exynos-drm on minor 0

It looks that handling of DDC i2c over DP AUX chanel (get_modes callback) is
not synchronized with enabling bridge in analogix_dp_set_bridge().

I'm surprised that you didn't observe similar issues on rk3399.

I've investigated this issue further and it turned out that the DDC/I2C AUX
channel timeout issue is related to the fact, that exynos_dp driver creates
additional connector for the display pipeline on Exynos5420 Chromebook2
Peach-PIT.

One connector is created by analogix_dp core, the second (the one which is
in fact operational) is created by parade_ps eDP/LVDS bridge. The DDC/I2C
AUX channel timeouts happens when DRM core tries to get mode from the
connector object created by analogix_dp core.

This patch fixes this issue:

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index db5a6b82815d..46b704adb2ae 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1195,27 +1195,30 @@ static int analogix_dp_bridge_attach(struct drm_bridge *bridge)
Â{
ÂÂÂÂ struct analogix_dp_device *dp = bridge->driver_private;
ÂÂÂÂ struct drm_encoder *encoder = dp->encoder;
-ÂÂÂ struct drm_connector *connector = &dp->connector;
-ÂÂÂ int ret;
+ÂÂÂ struct drm_connector *connector = NULL;
+ÂÂÂ int ret = 0;

ÂÂÂÂ if (!bridge->encoder) {
ÂÂÂÂ ÂÂÂ DRM_ERROR("Parent encoder object not found");
ÂÂÂÂ ÂÂÂ return -ENODEV;
ÂÂÂÂ }

-ÂÂÂ connector->polled = DRM_CONNECTOR_POLL_HPD;
+ÂÂÂ if (!dp->plat_data->skip_connector) {
+ÂÂÂ ÂÂÂ connector = &dp->connector;
+ÂÂÂ ÂÂÂ connector->polled = DRM_CONNECTOR_POLL_HPD;

-ÂÂÂ ret = drm_connector_init(dp->drm_dev, connector,
-ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ Â&analogix_dp_connector_funcs,
-ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂDRM_MODE_CONNECTOR_eDP);
-ÂÂÂ if (ret) {
-ÂÂÂ ÂÂÂ DRM_ERROR("Failed to initialize connector with drm\n");
-ÂÂÂ ÂÂÂ return ret;
-ÂÂÂ }
+ÂÂÂ ÂÂÂ ret = drm_connector_init(dp->drm_dev, connector,
+ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ Â&analogix_dp_connector_funcs,
+ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂDRM_MODE_CONNECTOR_eDP);
+ÂÂÂ ÂÂÂ if (ret) {
+ÂÂÂ ÂÂÂ ÂÂÂ DRM_ERROR("Failed to initialize connector with drm\n");
+ÂÂÂ ÂÂÂ ÂÂÂ return ret;
+ÂÂÂ ÂÂÂ }

-ÂÂÂ drm_connector_helper_add(connector,
-ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ Â&analogix_dp_connector_helper_funcs);
-ÂÂÂ drm_mode_connector_attach_encoder(connector, encoder);
+ÂÂÂ ÂÂÂ drm_connector_helper_add(connector,
+ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ Â&analogix_dp_connector_helper_funcs);
+ÂÂÂ ÂÂÂ drm_mode_connector_attach_encoder(connector, encoder);
+ÂÂÂ }

ÂÂÂÂ /*
ÂÂÂÂ Â* NOTE: the connector registration is implemented in analogix
diff --git a/drivers/gpu/drm/exynos/exynos_dp.c b/drivers/gpu/drm/exynos/exynos_dp.c
index b316249a3f89..86330f396784 100644
--- a/drivers/gpu/drm/exynos/exynos_dp.c
+++ b/drivers/gpu/drm/exynos/exynos_dp.c
@@ -244,6 +244,7 @@ static int exynos_dp_probe(struct platform_device *pdev)

ÂÂÂÂ /* The remote port can be either a panel or a bridge */
ÂÂÂÂ dp->plat_data.panel = panel;
+ÂÂÂ dp->plat_data.skip_connector = !!bridge;
ÂÂÂÂ dp->ptn_bridge = bridge;

Âout:
diff --git a/include/drm/bridge/analogix_dp.h b/include/drm/bridge/analogix_dp.h
index b384f7e8d14a..475b706b49de 100644
--- a/include/drm/bridge/analogix_dp.h
+++ b/include/drm/bridge/analogix_dp.h
@@ -31,6 +31,7 @@ struct analogix_dp_plat_data {
ÂÂÂÂ struct drm_panel *panel;
ÂÂÂÂ struct drm_encoder *encoder;
ÂÂÂÂ struct drm_connector *connector;
+ÂÂÂ bool skip_connector;

ÂÂÂÂ int (*power_on_start)(struct analogix_dp_plat_data *);
ÂÂÂÂ int (*power_on_end)(struct analogix_dp_plat_data *);
--

I'm still not convinced that the get_modes callback implementation and real
DDC/I2C AUX transfers are correctly handled in ExynosDP case, but I don't have
access to the hardware which would use them. Both Chromebook2 Peach-PIT and
Chromebook Snow have additional bridge between analogix_dp and the panel.

Frankly speaking, this issue reveals that the whole bridge-to-bridge,
connector, panel pipeline handling in the DRM drivers is a over-complicated
(over-engineered?) and there is a mess in the drivers.

There is one more issue even after above patch - disabling display pipeline
causes system hang. I've spent some more time debugging it and found that the
power off sequence in analogix_dp_bridge_disable() is incorrect. In case of
exynos_dp, external PHY also powers analogix_dp block, so any register access
after phy_power_off() is forbidden. The following patch fixes this issue:

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index ad8737384ab0..32c42d33c25e 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1349,8 +1349,8 @@ static void analogix_dp_bridge_disable(struct drm_bridge *bridge)
ÂÂÂÂ if (dp->plat_data->power_off)
ÂÂÂÂ ÂÂÂ dp->plat_data->power_off(dp->plat_data);

-ÂÂÂ phy_power_off(dp->phy);
ÂÂÂÂ analogix_dp_set_analog_power_down(dp, POWER_ALL, 1);
+ÂÂÂ phy_power_off(dp->phy);

ÂÂÂÂ clk_disable_unprepare(dp->clock);

With the above patch it looks that exynos_dp is now fully operational again.

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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