[Intel-gfx] [PATCH] drm/i915: Shut down displays gracefully on reboot

[David Weinehall]

On Mon, Aug 08, 2016 at 03:52:41PM +0300, Ville Syrjälä wrote:
> On Fri, Aug 05, 2016 at 03:45:19PM -0700, Clint Taylor wrote:
> > On 08/03/2016 06:36 AM, ville.syrjala at linux.intel.com wrote:
> > > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > >
> > > Dell UP2414Q doesn't like it when we're driving it in MST mode, and then
> > > reboot the machine. After reboot, the monitor is somehow confused and
> > > refuses to do the payload allocation:
> > >   [drm:drm_dp_mst_allocate_vcpi] initing vcpi for 282 8
> > >   [drm:drm_dp_dpcd_write_payload] status not set after read payload table status 0
> > > and thus we're left with a black screen until the monitor power is
> > > toggled.
> > >
> > > It seems that if we shut down things gracefully prior to rebooting, the
> > > monitor doesn't get confused like this. So let's try to shut down all
> > > the displays gracefully on reboot. The downside is that we will
> > > introduce the reboot notifier to all the modesetl locks. So if there's
> > > a locking bug around, we might not be able to reboot the machine
> > > gracefully. sysrq reboot will still work though, as it will not
> > > call the notifiers.
> > >
> > > While we do this, we can eliminate the eDP reboot notifier, which is
> > > there to shut down the panel power and make sure the firmware won't
> > > violate the panel power cycle delay post-reboot. Since we're now
> > > shutting eDP down properly, we can mostly just rip out the eDP notifier.
> > > We still need to do the panel power cycle wait though, as that would
> > > normally get postponed until the next modeset. So let's move that part
> > > into intel_panel so that other display types will get the same treatment
> > > as a bonus.
> > >
> > > The Dell UP2414Q can often get even more confused, and sometimes what
> > > you have to do is: switch to another input on the monitor, toggle the
> > > monitor power, switch the input back to the original setting. And
> > > sometimes it seems you just have to yank the power cable entirely. I'm
> > > not sure if this reboot notifier might avoid some of these other
> > > failure modes as well, but I'm pretty sure it can't hurt at least.
> > >
> > 
> > While testing this change on SKL if 2 crtc's are enabled resume from 
> > suspend is 500ms longer than a single crtc resume. Are we calling the 
> > T12 msleep(500) for non eDP panels?
> 
> Seems unlikely, unless we misdetect DP as eDP. 500ms sure sounds a lot
> for non-eDP though.

You can try this patch to get easy access to the timings to see if
they seem reasonable:


commit 7e88e096931065efebd43d844fe3bf106932a9fa
Author: David Weinehall <david.weinehall at linux.intel.com>
Date:   Thu Jul 21 13:36:49 2016 +0300

    drm/i915/debugfs: Add panel delays for eDP
    
    The eDP backlight and panel enable/disable delays are quite
    useful to know when measuring time consumed by suspend/resume,
    and while the information are printed to the kernel log as debug
    messages, having this information in debugfs makes things easier.
    
    Signed-off-by: David Weinehall <david.weinehall at linux.intel.com>

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index e726b02bdb5a..282d6716d012 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -5544,6 +5544,40 @@ static const struct file_operations i915_dpcd_fops = {
 	.release = single_release,
 };
 
+static int i915_panel_show(struct seq_file *m, void *data)
+{
+	struct drm_connector *connector = m->private;
+	struct intel_dp *intel_dp =
+		enc_to_intel_dp(&intel_attached_encoder(connector)->base);
+
+	if (connector->status != connector_status_connected)
+		return -ENODEV;
+
+	seq_printf(m, "Panel power up delay: %d\n",
+		   intel_dp->panel_power_up_delay);
+	seq_printf(m, "Panel power down delay: %d\n",
+		   intel_dp->panel_power_down_delay);
+	seq_printf(m, "Backlight on delay: %d\n",
+		   intel_dp->backlight_on_delay);
+	seq_printf(m, "Backlight off delay: %d\n",
+		   intel_dp->backlight_off_delay);
+
+	return 0;
+}
+
+static int i915_panel_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, i915_panel_show, inode->i_private);
+}
+
+static const struct file_operations i915_panel_fops = {
+	.owner = THIS_MODULE,
+	.open = i915_panel_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
 /**
  * i915_debugfs_connector_add - add i915 specific connector debugfs files
  * @connector: pointer to a registered drm_connector
@@ -5563,8 +5597,12 @@ int i915_debugfs_connector_add(struct drm_connector *connector)
 
 	if (connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort ||
 	    connector->connector_type == DRM_MODE_CONNECTOR_eDP)
-		debugfs_create_file("i915_dpcd", S_IRUGO, root, connector,
-				    &i915_dpcd_fops);
+		debugfs_create_file("i915_dpcd", S_IRUGO, root,
+				    connector, &i915_dpcd_fops);
+
+	if (connector->connector_type == DRM_MODE_CONNECTOR_eDP)
+		debugfs_create_file("i915_panel_timings", S_IRUGO, root,
+				    connector, &i915_panel_fops);
 
 	return 0;
 }