[Bug 109522] drm:intel_dp_start_link_train [i915] *ERROR* failed to enable link training

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=109522

--- Comment #29 from howaboutsynergy at pm.me ---
Created attachment 144653
  --> https://bugs.freedesktop.org/attachment.cgi?id=144653&action=edit
dmesg with drm.debug-0x1e on drm-tip (only within X)

Used this drm-tip:
commit cc7ffe2a301509ba233652ec17d0f74c18b5c8a9 (HEAD -> drm-tip,
origin/drm-tip, origin/HEAD)
Date:   Thu Jun 27 10:28:10 2019 +0200

    drm-tip: 2019y-06m-27d-08h-26m-31s UTC integration manifest

Had the following changes in `drivers/gpu/drm/` so that hopefully dumping the
stack each time -110 was hit(1+13 times) is helpful to see in the dmesg,
however this does increase the time spent(by about 4-5 seconds total), so let
me know if you want me to undo this and repost one clean-ish without it.

```patch
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index b9362b4f6353..c5f7f4c37565 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -76,7 +76,7 @@ config DRM_KMS_FB_HELPER
        bool
        depends on DRM_KMS_HELPER
        select FB
-       select FRAMEBUFFER_CONSOLE if !EXPERT
+       select FRAMEBUFFER_CONSOLE
        select FRAMEBUFFER_CONSOLE_DETECT_PRIMARY if FRAMEBUFFER_CONSOLE
        select FB_SYS_FOPS
        select FB_SYS_FILLRECT
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 0b994d083a89..92b2199af2ad 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -264,10 +264,12 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8
request,
                        err = ret;
        }

-       DRM_DEBUG_KMS("Too many retries, giving up. First error: %d\n", err);
+       DRM_ERROR("Too many retries, giving up. First error: %d\n", err);
+  dump_stack();
        ret = err;

 unlock:
+       DRM_ERROR("Ret '%d' after %u retries\n", ret, retry);
        mutex_unlock(&aux->hw_mutex);
        return ret;
 }
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 1984e5c54d58..60004f8ae03a 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -2379,7 +2379,7 @@ EXPORT_SYMBOL(drm_fbdev_generic_setup);
  */
 int __init drm_fb_helper_modinit(void)
 {
-#if defined(CONFIG_FRAMEBUFFER_CONSOLE_MODULE) && !defined(CONFIG_EXPERT)
+#if defined(CONFIG_FRAMEBUFFER_CONSOLE_MODULE) && ( !defined(CONFIG_EXPERT) ||
defined(CONFIG_DRM_MODULE) || defined(CONFIG_DRM) )
        const char name[] = "fbcon";
        struct module *fbcon;

diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index 9b1fccea966b..1242cf9e9828 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -89,6 +89,7 @@ intel_dp_set_link_train(struct intel_dp *intel_dp,
        ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET,
                                buf, len);

+  DRM_ERROR("ret=%d len=%d\n", ret, len);
        return ret == len;
 }

```

For full set of changes(including actual .config file used) see:
https://gist.github.com/howaboutsynergy/9b6e890ec15592a55a0c07b5db234ce6

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