[PATCH 1/2] drm: Introduce crtc->mode_valid() callback

[Jose Abreu]

Some crtc's may have restrictions in the mode they can display. In
this patch a new callback (crtc->mode_valid()) is introduced that
is called at the same stage of connector->mode_valid() callback.

This shall be implemented if the crtc has some sort of restriction
so that we don't probe modes that will fail in the commit() stage.
For example: A given crtc may be responsible to set a clock value.
If the clock can not produce all the values for the available
modes then this callback can be used to restrict the number of
probbed modes to only the ones that can be displayed.

If the crtc does not implement the callback then the behaviour will
remain the same. Also, for a given set of crtcs that can be bound to
the connector, if at least one can display the mode then the mode
will be probbed.

Signed-off-by: Jose Abreu <joabreu@xxxxxxxxxxxx>
Cc: Carlos Palminha <palminha@xxxxxxxxxxxx>
Cc: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
Cc: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxx>
---
 drivers/gpu/drm/drm_probe_helper.c       | 44 ++++++++++++++++++++++++++++++++
 include/drm/drm_modeset_helper_vtables.h | 26 +++++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 1b0c14a..61eac30 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -80,6 +80,46 @@
 	return MODE_OK;
 }
 
+static enum drm_mode_status drm_mode_validate_connector_crtc(
+		struct drm_connector *connector,
+		struct drm_display_mode *mode)
+{
+	const struct drm_crtc_helper_funcs *crtc_funcs = NULL;
+	enum drm_mode_status mode_status = MODE_ERROR;
+	struct drm_device *dev = connector->dev;
+	struct drm_encoder *encoder;
+	struct drm_crtc *crtc;
+	bool callback_found = false;
+	int i;
+
+	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++) {
+		encoder = drm_encoder_find(dev, connector->encoder_ids[i]);
+
+		if (!encoder)
+			continue;
+
+		drm_for_each_crtc(crtc, dev) {
+			crtc_funcs = crtc->helper_private;
+
+			if (!drm_encoder_crtc_ok(encoder, crtc))
+				continue;
+			if (!crtc_funcs || !crtc_funcs->mode_valid)
+				continue;
+
+			/* MODE_OK=0 and default mode_status=MODE_ERROR=-1
+			 * so if at least one crtc accepts the mode we get
+			 * MODE_OK */
+			mode_status &= crtc_funcs->mode_valid(crtc, mode);
+			callback_found |= true;
+		}
+	}
+
+	/* We can reach here without calling mode_valid if there is no
+	 * registered crtc with this callback, lets return MODE_OK in this
+	 * case */
+	return callback_found ? mode_status : MODE_OK;
+}
+
 static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
 {
 	struct drm_cmdline_mode *cmdline_mode;
@@ -431,6 +471,10 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
 		if (mode->status == MODE_OK && connector_funcs->mode_valid)
 			mode->status = connector_funcs->mode_valid(connector,
 								   mode);
+
+		if (mode->status == MODE_OK)
+			mode->status = drm_mode_validate_connector_crtc(
+					connector, mode);
 	}
 
 prune:
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index c01c328..59fffba 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -106,6 +106,32 @@ struct drm_crtc_helper_funcs {
 	void (*commit)(struct drm_crtc *crtc);
 
 	/**
+	 * @mode_valid:
+	 *
+	 * This callback should be implemented if the crtc has some sort of
+	 * restriction in the modes it can display. For example, a given crtc
+	 * may be responsible to set a clock value. If the clock can not
+	 * produce all the values for the available modes then this callback
+	 * can be used to restrict the number of probbed modes to only the ones
+	 * that can be displayed.
+	 *
+	 * This is directly called at the same stage of connector->mode_valid
+	 * callback.
+	 *
+	 * NOTE:
+	 *
+	 * For a given set of crtc's in a drm_device, if at least one does not
+	 * have the mode_valid callback, or, at least one returns MODE_OK then
+	 * the mode will be probbed.
+	 *
+	 * RETURNS:
+	 *
+	 * drm_mode_status Enum
+	 */
+	enum drm_mode_status (*mode_valid)(struct drm_crtc *crtc,
+			struct drm_display_mode *mode);
+
+	/**
 	 * @mode_fixup:
 	 *
 	 * This callback is used to validate a mode. The parameter mode is the
-- 
1.9.1