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From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: DRI Development <dri-devel@lists.freedesktop.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	Thierry Reding <treding@nvidia.com>,
	John Stultz <john.stultz@linaro.org>,
	Liviu Dudau <liviu@dudau.co.uk>
Subject: [PATCH] drm/fb-helper: Support deferred setup
Date: Wed, 28 Jun 2017 13:32:01 +0200	[thread overview]
Message-ID: <20170628113201.27383-1-daniel.vetter@ffwll.ch> (raw)
In-Reply-To: <20170627145936.18983-11-daniel.vetter@ffwll.ch>

FB helper code falls back to a 1024x768 mode if no outputs are connected
or don't report back any modes upon initialization. This can be annoying
because outputs that are added to FB helper later on can't be used with
FB helper if they don't support a matching mode.

The fallback is in place because VGA connectors can happen to report an
unknown connection status even when they are in fact connected.

Some drivers have custom solutions in place to defer FB helper setup
until at least one output is connected. But the logic behind these
solutions is always the same and there is nothing driver-specific about
it, so a better alterative is to fix the FB helper core and add support
for all drivers automatically.

This patch adds support for deferred FB helper setup. It checks all the
connectors for their connection status, and if all of them report to be
disconnected marks the FB helper as needing deferred setup. Whet setup
is deferred, the FB helper core will automatically retry setup after a
hotplug event, and it will keep trying until it succeeds.

v2: Rebase onto my entirely reworked fbdev helper locking. One big
difference is that this version again drops&reacquires the fbdev lock
(which is now fb_helper->lock, but before this patch series it was
mode_config->mutex), because register_framebuffer must be able to
recurse back into fbdev helper code for the initial screen setup.

v3: __drm_fb_helper_initial_config must hold fb_helper->lock upon
return, I've fumbled that in the deferred setup case (Liviu).

v4: I was blind, redo this all. __drm_fb_helper_initial_config
shouldn't need to reacquire fb_helper->lock, that just confuses
callers. I myself got confused by kernel_fb_helper_lock and somehow
thought it's the same as fb_helper->lock. Tsk.

Also simplify the logic a bit (we don't need two functions to probe
connectors), we can stick much closer to the existing code. And update
some comments I've spotted that are outdated.

v5: Don't pass -EAGAIN to drivers, it's just an internal error code
(Liviu).

Cc: Liviu Dudau <liviu@dudau.co.uk>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thierry Reding <treding@nvidia.com> (v1)
Tested-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com> (v1)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/drm_fb_helper.c | 101 ++++++++++++++++++++++++++--------------
 include/drm/drm_fb_helper.h     |  23 +++++++++
 2 files changed, 89 insertions(+), 35 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index bbd4c6d0378d..e49bae10f0ee 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -521,6 +521,9 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
 	if (!drm_fbdev_emulation)
 		return -ENODEV;
 
+	if (READ_ONCE(fb_helper->deferred_setup))
+		return 0;
+
 	mutex_lock(&fb_helper->lock);
 	ret = restore_fbdev_mode(fb_helper);
 
@@ -1695,8 +1698,7 @@ EXPORT_SYMBOL(drm_fb_helper_pan_display);
 
 /*
  * Allocates the backing storage and sets up the fbdev info structure through
- * the ->fb_probe callback and then registers the fbdev and sets up the panic
- * notifier.
+ * the ->fb_probe callback.
  */
 static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
 					 int preferred_bpp)
@@ -1794,13 +1796,8 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
 	}
 
 	if (crtc_count == 0 || sizes.fb_width == -1 || sizes.fb_height == -1) {
-		/*
-		 * hmm everyone went away - assume VGA cable just fell out
-		 * and will come back later.
-		 */
-		DRM_INFO("Cannot find any crtc or sizes - going 1024x768\n");
-		sizes.fb_width = sizes.surface_width = 1024;
-		sizes.fb_height = sizes.surface_height = 768;
+		DRM_INFO("Cannot find any crtc or sizes\n");
+		return -EAGAIN;
 	}
 
 	/* Handle our overallocation */
@@ -2429,6 +2426,58 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper,
 	kfree(enabled);
 }
 
+/* Note: Drops fb_helper->lock before returning. */
+static int __drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper,
+					  int bpp_sel)
+{
+	struct drm_device *dev = fb_helper->dev;
+	struct fb_info *info;
+	unsigned int width, height;
+	int ret;
+
+	width = dev->mode_config.max_width;
+	height = dev->mode_config.max_height;
+
+	drm_setup_crtcs(fb_helper, width, height);
+	ret = drm_fb_helper_single_fb_probe(fb_helper, bpp_sel);
+	if (ret < 0) {
+		if (ret == -EAGAIN) {
+			fb_helper->preferred_bpp = bpp_sel;
+			fb_helper->deferred_setup = true;
+			ret = 0;
+		}
+		mutex_unlock(&fb_helper->lock);
+
+		return ret;
+	}
+
+	fb_helper->deferred_setup = false;
+
+	info = fb_helper->fbdev;
+	info->var.pixclock = 0;
+
+	/* Need to drop locks to avoid recursive deadlock in
+	 * register_framebuffer. This is ok because the only thing left to do is
+	 * register the fbdev emulation instance in kernel_fb_helper_list. */
+	mutex_unlock(&fb_helper->lock);
+
+	ret = register_framebuffer(info);
+	if (ret < 0)
+		return ret;
+
+	dev_info(dev->dev, "fb%d: %s frame buffer device\n",
+		 info->node, info->fix.id);
+
+	mutex_lock(&kernel_fb_helper_lock);
+	if (list_empty(&kernel_fb_helper_list))
+		register_sysrq_key('v', &sysrq_drm_fb_helper_restore_op);
+
+	list_add(&fb_helper->kernel_fb_list, &kernel_fb_helper_list);
+	mutex_unlock(&kernel_fb_helper_lock);
+
+	return 0;
+}
+
 /**
  * drm_fb_helper_initial_config - setup a sane initial connector configuration
  * @fb_helper: fb_helper device struct
@@ -2473,39 +2522,15 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper,
  */
 int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper, int bpp_sel)
 {
-	struct drm_device *dev = fb_helper->dev;
-	struct fb_info *info;
 	int ret;
 
 	if (!drm_fbdev_emulation)
 		return 0;
 
 	mutex_lock(&fb_helper->lock);
-	drm_setup_crtcs(fb_helper,
-			dev->mode_config.max_width,
-			dev->mode_config.max_height);
-	ret = drm_fb_helper_single_fb_probe(fb_helper, bpp_sel);
-	mutex_unlock(&fb_helper->lock);
-	if (ret)
-		return ret;
+	ret = __drm_fb_helper_initial_config(fb_helper, bpp_sel);
 
-	info = fb_helper->fbdev;
-	info->var.pixclock = 0;
-	ret = register_framebuffer(info);
-	if (ret < 0)
-		return ret;
-
-	dev_info(dev->dev, "fb%d: %s frame buffer device\n",
-		 info->node, info->fix.id);
-
-	mutex_lock(&kernel_fb_helper_lock);
-	if (list_empty(&kernel_fb_helper_list))
-		register_sysrq_key('v', &sysrq_drm_fb_helper_restore_op);
-
-	list_add(&fb_helper->kernel_fb_list, &kernel_fb_helper_list);
-	mutex_unlock(&kernel_fb_helper_lock);
-
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL(drm_fb_helper_initial_config);
 
@@ -2538,6 +2563,12 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
 		return 0;
 
 	mutex_lock(&fb_helper->lock);
+	if (fb_helper->deferred_setup) {
+		err = __drm_fb_helper_initial_config(fb_helper,
+						     fb_helper->preferred_bpp);
+		return err;
+	}
+
 	if (!fb_helper->fb || !drm_fb_helper_is_bound(fb_helper)) {
 		fb_helper->delayed_hotplug = true;
 		mutex_unlock(&fb_helper->lock);
diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index ea170b96e88d..a5ea6ffdfecc 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -232,6 +232,29 @@ struct drm_fb_helper {
 	 * needs to be reprobe when fbdev is in control again.
 	 */
 	bool delayed_hotplug;
+
+	/**
+	 * @deferred_setup:
+	 *
+	 * If no outputs are connected (disconnected or unknown) the FB helper
+	 * code will defer setup until at least one of the outputs shows up.
+	 * This field keeps track of the status so that setup can be retried
+	 * at every hotplug event until it succeeds eventually.
+	 *
+	 * Protected by @lock.
+	 */
+	bool deferred_setup;
+
+	/**
+	 * @preferred_bpp:
+	 *
+	 * Temporary storage for the driver's preferred BPP setting passed to
+	 * FB helper initialization. This needs to be tracked so that deferred
+	 * FB helper setup can pass this on.
+	 *
+	 * See also: @deferred_setup
+	 */
+	int preferred_bpp;
 };
 
 /**
-- 
2.11.0

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  reply	other threads:[~2017-06-28 11:32 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-27 14:59 [PATCH 00/13] fbdev locking rework and deferred setup, take 2 Daniel Vetter
2017-06-27 14:59 ` [PATCH 01/13] drm/fb-helper: Push down modeset lock into FB helpers Daniel Vetter
2017-06-29  9:10   ` Maarten Lankhorst
2017-06-29  9:23     ` Daniel Vetter
2017-06-29  9:33       ` Maarten Lankhorst
2017-06-29  9:44         ` Daniel Vetter
2017-06-29 11:13           ` Maarten Lankhorst
2017-06-29 12:38             ` Daniel Vetter
2017-06-27 14:59 ` [PATCH 02/13] drm/i915: Drop FBDEV #ifdev in mst code Daniel Vetter
2017-06-27 14:59 ` [PATCH 03/13] drm/fb-helper: Add top-level lock Daniel Vetter
2017-06-27 14:59 ` [PATCH 04/13] drm/fb-helper: Push locking in fb_is_bound Daniel Vetter
2017-06-27 14:59 ` [PATCH 05/13] drm/fb-helper: Drop locking from the vsync wait ioctl code Daniel Vetter
2017-06-27 14:59 ` [PATCH 06/13] drm/fb-helper: Push locking into pan_display_atomic|legacy Daniel Vetter
2017-06-27 14:59 ` [PATCH 07/13] drm/fb-helper: Push locking into restore_fbdev_mode_atomic|legacy Daniel Vetter
2017-06-27 14:59 ` [PATCH 08/13] drm/fb-helper: Stop using mode_config.mutex for internals Daniel Vetter
2017-06-27 14:59 ` [PATCH 09/13] drm/fb-helper: Split dpms handling into legacy and atomic paths Daniel Vetter
2017-06-29 10:22   ` Maarten Lankhorst
2017-06-29 10:31     ` Daniel Vetter
2017-06-29 10:58       ` Maarten Lankhorst
2017-06-29 11:00         ` Daniel Vetter
2017-06-29 11:23           ` Maarten Lankhorst
2017-06-27 14:59 ` [PATCH 10/13] drm/fb-helper: Support deferred setup Daniel Vetter
2017-06-28 11:32   ` Daniel Vetter [this message]
2017-06-28 16:24     ` [PATCH] " Liviu Dudau
2017-06-29 10:59     ` Maarten Lankhorst
2017-06-29 12:36       ` Daniel Vetter
2017-06-30 16:51     ` [PATCH] drm/fb-helper: Restore first connection behaviour on " Liviu Dudau
2017-06-30 18:13       ` Daniel Vetter
2017-07-03  8:44         ` Liviu Dudau
2017-07-03 16:33           ` Daniel Vetter
2017-06-27 14:59 ` [PATCH 11/13] drm/exynos: Remove custom FB helper " Daniel Vetter
2017-06-27 14:59 ` [PATCH 12/13] drm/hisilicon: " Daniel Vetter
2017-06-28  9:08   ` [PATCH] " Daniel Vetter
2017-06-27 14:59 ` [PATCH 13/13] drm/atomic-helper: Realign function parameters Daniel Vetter
2017-06-27 15:01   ` Deucher, Alexander
2017-06-27 15:42   ` Harry Wentland
2017-07-04 15:16     ` Daniel Vetter
2017-06-27 15:30 ` ✓ Fi.CI.BAT: success for fbdev locking rework and deferred setup, take 2 Patchwork
2017-06-27 23:02 ` [PATCH 00/13] " John Stultz
2017-06-28  7:36   ` Daniel Vetter
2017-06-28  9:28 ` ✓ Fi.CI.BAT: success for fbdev locking rework and deferred setup, take 2 (rev2) Patchwork
2017-06-28 12:28 ` ✓ Fi.CI.BAT: success for fbdev locking rework and deferred setup, take 2 (rev3) Patchwork
  -- strict thread matches above, loose matches on Subject: below --
2017-06-21 18:28 [PATCH 10/12] drm/fb-helper: Support deferred setup Daniel Vetter
2017-06-23 13:31 ` [PATCH] " Daniel Vetter

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