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 And update some comments I've spotted that are outdated.
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 | 100 ++++++++++++++++++++++++++-------------- include/drm/drm_fb_helper.h | 23 +++++++++ 2 files changed, 88 insertions(+), 35 deletions(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index bbd4c6d0378d..d833eb2320d1 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 +2426,57 @@ 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; + } + 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 +2521,15 @@ 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 +2562,12 @@ 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; };
/**