drm/modes: Allow to specify rotation and reflection on the commandline

Rotations and reflections setup are needed in some scenarios to initialise
properly the initial framebuffer. Some drivers already had a bunch of
quirks to deal with this, such as either a private kernel command line
parameter (omapdss) or on the device tree (various panels).

In order to accomodate this, let's create a video mode parameter to deal
with the rotation and reflexion.
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/777da16e42db757c1f5b414b5ca34507097fed5c.1560783090.git-series.maxime.ripard@bootlin.com

Documentation/fb/modedb.txt

@@ -51,6 +51,18 @@ To force the VGA output to be enabled and drive a specific mode say:
 Specifying the option multiple times for different ports is possible, e.g.:
     video=LVDS-1:d video=HDMI-1:D
 
+Options can also be passed after the mode, using commas as separator.
+
+       Sample usage: 720x480,rotate=180 - 720x480 mode, rotated by 180 degrees
+
+Valid options are:
+
+  - reflect_x (boolean): Perform an axial symmetry on the X axis
+  - reflect_y (boolean): Perform an axial symmetry on the Y axis
+  - rotate (integer): Rotate the initial framebuffer by x
+    degrees. Valid values are 0, 90, 180 and 270.
+
+
 ***** oOo ***** oOo ***** oOo ***** oOo ***** oOo ***** oOo ***** oOo *****
 
 What is the VESA(TM) Coordinated Video Timings (CVT)?

drivers/gpu/drm/drm_client_modeset.c

@@ -824,6 +824,7 @@ bool drm_client_rotation(struct drm_mode_set *modeset, unsigned int *rotation)
 {
 	struct drm_connector *connector = modeset->connectors[0];
 	struct drm_plane *plane = modeset->crtc->primary;
+	struct drm_cmdline_mode *cmdline;
 	u64 valid_mask = 0;
 	unsigned int i;
 
@@ -844,6 +845,35 @@ bool drm_client_rotation(struct drm_mode_set *modeset, unsigned int *rotation)
 		*rotation = DRM_MODE_ROTATE_0;
 	}
 
+	/**
+	 * The panel already defined the default rotation
+	 * through its orientation. Whatever has been provided
+	 * on the command line needs to be added to that.
+	 *
+	 * Unfortunately, the rotations are at different bit
+	 * indices, so the math to add them up are not as
+	 * trivial as they could.
+	 *
+	 * Reflections on the other hand are pretty trivial to deal with, a
+	 * simple XOR between the two handle the addition nicely.
+	 */
+	cmdline = &connector->cmdline_mode;
+	if (cmdline->specified) {
+		unsigned int cmdline_rest, panel_rest;
+		unsigned int cmdline_rot, panel_rot;
+		unsigned int sum_rot, sum_rest;
+
+		panel_rot = ilog2(*rotation & DRM_MODE_ROTATE_MASK);
+		cmdline_rot = ilog2(cmdline->rotation_reflection & DRM_MODE_ROTATE_MASK);
+		sum_rot = (panel_rot + cmdline_rot) % 4;
+
+		panel_rest = *rotation & ~DRM_MODE_ROTATE_MASK;
+		cmdline_rest = cmdline->rotation_reflection & ~DRM_MODE_ROTATE_MASK;
+		sum_rest = panel_rest ^ cmdline_rest;
+
+		*rotation = (1 << sum_rot) | sum_rest;
+	}
+
 	/*
 	 * TODO: support 90 / 270 degree hardware rotation,
 	 * depending on the hardware this may require the framebuffer

drivers/gpu/drm/drm_modes.c

@@ -1554,6 +1554,71 @@ static int drm_mode_parse_cmdline_res_mode(const char *str, unsigned int length,
 	return 0;
 }
 
+static int drm_mode_parse_cmdline_options(char *str, size_t len,
+					  struct drm_connector *connector,
+					  struct drm_cmdline_mode *mode)
+{
+	unsigned int rotation = 0;
+	char *sep = str;
+
+	while ((sep = strchr(sep, ','))) {
+		char *delim, *option;
+
+		option = sep + 1;
+		delim = strchr(option, '=');
+		if (!delim) {
+			delim = strchr(option, ',');
+
+			if (!delim)
+				delim = str + len;
+		}
+
+		if (!strncmp(option, "rotate", delim - option)) {
+			const char *value = delim + 1;
+			unsigned int deg;
+
+			deg = simple_strtol(value, &sep, 10);
+
+			/* Make sure we have parsed something */
+			if (sep == value)
+				return -EINVAL;
+
+			switch (deg) {
+			case 0:
+				rotation |= DRM_MODE_ROTATE_0;
+				break;
+
+			case 90:
+				rotation |= DRM_MODE_ROTATE_90;
+				break;
+
+			case 180:
+				rotation |= DRM_MODE_ROTATE_180;
+				break;
+
+			case 270:
+				rotation |= DRM_MODE_ROTATE_270;
+				break;
+
+			default:
+				return -EINVAL;
+			}
+		} else if (!strncmp(option, "reflect_x", delim - option)) {
+			rotation |= DRM_MODE_REFLECT_X;
+			sep = delim;
+		} else if (!strncmp(option, "reflect_y", delim - option)) {
+			rotation |= DRM_MODE_REFLECT_Y;
+			sep = delim;
+		} else {
+			return -EINVAL;
+		}
+	}
+
+	mode->rotation_reflection = rotation;
+
+	return 0;
+}
+
 /**
  * drm_mode_parse_command_line_for_connector - parse command line modeline for connector
  * @mode_option: optional per connector mode option
@@ -1569,6 +1634,10 @@ static int drm_mode_parse_cmdline_res_mode(const char *str, unsigned int length,
  *
  *	<xres>x<yres>[M][R][-<bpp>][@<refresh>][i][m][eDd]
  *
+ * Additionals options can be provided following the mode, using a comma to
+ * separate each option. Valid options can be found in
+ * Documentation/fb/modedb.txt.
+ *
  * The intermediate drm_cmdline_mode structure is required to store additional
  * options from the command line modline like the force-enable/disable flag.
  *
@@ -1581,9 +1650,10 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
 {
 	const char *name;
 	bool named_mode = false, parse_extras = false;
-	unsigned int bpp_off = 0, refresh_off = 0;
+	unsigned int bpp_off = 0, refresh_off = 0, options_off = 0;
 	unsigned int mode_end = 0;
 	char *bpp_ptr = NULL, *refresh_ptr = NULL, *extra_ptr = NULL;
+	char *options_ptr = NULL;
 	char *bpp_end_ptr = NULL, *refresh_end_ptr = NULL;
 	int ret;
 
@@ -1632,13 +1702,18 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
 		mode->refresh_specified = true;
 	}
 
+	/* Locate the start of named options */
+	options_ptr = strchr(name, ',');
+	if (options_ptr)
+		options_off = options_ptr - name;
+
 	/* Locate the end of the name / resolution, and parse it */
-	if (bpp_ptr && refresh_ptr) {
-		mode_end = min(bpp_off, refresh_off);
-	} else if (bpp_ptr) {
+	if (bpp_ptr) {
 		mode_end = bpp_off;
 	} else if (refresh_ptr) {
 		mode_end = refresh_off;
+	} else if (options_ptr) {
+		mode_end = options_off;
 	} else {
 		mode_end = strlen(name);
 		parse_extras = true;
@@ -1680,25 +1755,24 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
 	else if (refresh_ptr)
 		extra_ptr = refresh_end_ptr;
 
-	if (extra_ptr) {
-		if (!named_mode) {
+	if (extra_ptr &&
+	    extra_ptr != options_ptr) {
 		int len = strlen(name) - (extra_ptr - name);
 
 		ret = drm_mode_parse_cmdline_extra(extra_ptr, len,
 						   connector, mode);
 		if (ret)
 			return false;
-		} else {
-			int remaining = strlen(name) - (extra_ptr - name);
+	}
 
-			/*
-			 * We still have characters to process, while
-			 * we shouldn't have any
-			 */
-			if (remaining > 0)
+	if (options_ptr) {
+		int len = strlen(name) - (options_ptr - name);
+
+		ret = drm_mode_parse_cmdline_options(options_ptr, len,
+						     connector, mode);
+		if (ret)
 			return false;
 	}
-	}
 
 	return true;
 }

include/drm/drm_connector.h

@@ -1025,6 +1025,16 @@ struct drm_cmdline_mode {
 	 * state to one of the DRM_FORCE_* values.
 	 */
 	enum drm_connector_force force;
+
+	/**
+	 * @rotation_reflection:
+	 *
+	 * Initial rotation and reflection of the mode setup from the
+	 * command line. See DRM_MODE_ROTATE_* and
+	 * DRM_MODE_REFLECT_*. The only rotations supported are
+	 * DRM_MODE_ROTATE_0 and DRM_MODE_ROTATE_180.
+	 */
+	unsigned int rotation_reflection;
 };
 
 /**