fbdev: sh_mobile_hdmi: add command line option to use the preferred EDID mode

Currently, if no command-line option is specified, the sh_mobile_hdmi
will use the default 720p video mode. If a command line option of the
form "video=sh_mobile_lcdc:<width>x<height>@<refresh>" is provided,
the driver will look for that mode among those, available in the
monitor EDID. This patch adds the ability to request the driver to
use monitor's preferred mode by specifying 0 as width and hight in
the above string. If that mode is not supported by the system, the
driver will continue scanning through EDID modes, until it finds a
suitable one.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 41 insertions, 19 deletions

diff --git a/drivers/video/sh_mobile_hdmi.c b/drivers/video/sh_mobile_hdmi.c
index 8c59cc8c5a9c..571bd9f74513 100644
--- a/drivers/video/sh_mobile_hdmi.c
+++ b/drivers/video/sh_mobile_hdmi.c
@@ -737,7 +737,7 @@ static int sh_hdmi_read_edid(struct sh_hdmi *hdmi, unsigned long *hdmi_rate,
         struct fb_modelist *modelist = NULL;
         unsigned int f_width = 0, f_height = 0, f_refresh = 0;
         unsigned long found_rate_error = ULONG_MAX; /* silly compiler... */
-        bool exact_match = false;
+        bool scanning = false, preferred_bad = false;
         u8 edid[128];
         char *forced;
         int i;
@@ -800,6 +800,9 @@ static int sh_hdmi_read_edid(struct sh_hdmi *hdmi, unsigned long *hdmi_rate,
                 if (i < 2) {
                         f_width = 0;
                         f_height = 0;
+                } else {
+                        /* The user wants us to use the EDID data */
+                        scanning = true;
                 }
                 dev_dbg(hdmi->dev, "Forced mode %ux%u@%uHz\n",
                         f_width, f_height, f_refresh);
@@ -807,37 +810,56 @@ static int sh_hdmi_read_edid(struct sh_hdmi *hdmi, unsigned long *hdmi_rate,
 
         /* Walk monitor modes to find the best or the exact match */
         for (i = 0, mode = hdmi->monspec.modedb;
-             f_width && f_height && i < hdmi->monspec.modedb_len && !exact_match;
+             i < hdmi->monspec.modedb_len && scanning;
              i++, mode++) {
                 unsigned long rate_error;
 
-                /* No interest in unmatching modes */
-                if (f_width != mode->xres || f_height != mode->yres)
+                if (!f_width && !f_height) {
+                        /*
+                         * A parameter string "video=sh_mobile_lcdc:0x0" means
+                         * use the preferred EDID mode. If it is rejected by
+                         * .fb_check_var(), keep looking, until an acceptable
+                         * one is found.
+                         */
+                        if ((mode->flag & FB_MODE_IS_FIRST) || preferred_bad)
+                                scanning = false;
+                        else
+                                continue;
+                } else if (f_width != mode->xres || f_height != mode->yres) {
+                        /* No interest in unmatching modes */
                         continue;
+                }
 
                 rate_error = sh_hdmi_rate_error(hdmi, mode, hdmi_rate, parent_rate);
 
-                if (f_refresh == mode->refresh || (!f_refresh && !rate_error))
-                        /*
-                         * Exact match if either the refresh rate matches or it
-                         * hasn't been specified and we've found a mode, for
-                         * which we can configure the clock precisely
-                         */
-                        exact_match = true;
-                else if (found && found_rate_error <= rate_error)
-                        /*
-                         * We otherwise search for the closest matching clock
-                         * rate - either if no refresh rate has been specified
-                         * or we cannot find an exactly matching one
-                         */
-                        continue;
+                if (scanning) {
+                        if (f_refresh == mode->refresh || (!f_refresh && !rate_error))
+                                /*
+                                 * Exact match if either the refresh rate
+                                 * matches or it hasn't been specified and we've
+                                 * found a mode, for which we can configure the
+                                 * clock precisely
+                                 */
+                                scanning = false;
+                        else if (found && found_rate_error <= rate_error)
+                                /*
+                                 * We otherwise search for the closest matching
+                                 * clock rate - either if no refresh rate has
+                                 * been specified or we cannot find an exactly
+                                 * matching one
+                                 */
+                                continue;
+                }
 
                 /* Check if supported: sufficient fb memory, supported clock-rate */
                 fb_videomode_to_var(var, mode);
 
+                var->bits_per_pixel = info->var.bits_per_pixel;
+
                 if (info && info->fbops->fb_check_var &&
                     info->fbops->fb_check_var(var, info)) {
-                        exact_match = false;
+                        scanning = true;
+                        preferred_bad = true;
                         continue;
                 }