Provide "quick" option for loading database into RAM

The directory cache and the database's Load to RAM feature
each result in a much better user experience.

But, when both features are enabled at the same time, it
can take a very long time on older players - easily several
minutes for larger libraries - until all of the database's
dircache references have been updated.

Include a 'Quick' option that causes the database to ignore
dircache references which can *significantly* reduce disk
activity after booting.

Change-Id: I25ae779c97d03885b06d5a28d8be55c0d05692a5

apps/lang/english.lang

@@ -16669,3 +16669,17 @@
     *: "Remove Queued Tracks?"
   </voice>
 </phrase>
+<phrase>
+  id: LANG_QUICK_IGNORE_DIRACHE
+  desc: in Settings
+  user: core
+  <source>
+    *: "Quick (Ignore Directory Cache)"
+  </source>
+  <dest>
+    *: "Quick (Ignore Directory Cache)"
+  </dest>
+  <voice>
+    *: "Quick (Ignore Directory Cache)"
+  </voice>
+</phrase>

apps/settings.h

@@ -136,6 +136,13 @@ enum
 };
 #endif
 
+enum
+{
+    TAGCACHE_RAM_OFF = 0,
+    TAGCACHE_RAM_ON = 1,
+    TAGCACHE_RAM_QUICK = 2
+};
+
 /* dir filter options */
 /* Note: Any new filter modes need to be added before NUM_FILTER_MODES.
  *       Any new rockbox browse filter modes (accessible through the menu)
@@ -576,7 +583,7 @@ struct user_settings
 #endif
 #ifdef HAVE_TAGCACHE
 #ifdef HAVE_TC_RAMCACHE
-    bool tagcache_ram;        /* load tagcache to ram? */
+    int tagcache_ram;        /* load tagcache to ram: 1=on, 2=quick (ignore dircache) */
 #endif
     bool tagcache_autoupdate; /* automatically keep tagcache in sync? */
     bool autoresume_enable;   /* enable auto-resume feature? */

apps/settings_list.c

@@ -1813,7 +1813,10 @@ const struct settings_list settings[] = {
 
 #ifdef HAVE_TAGCACHE
 #ifdef HAVE_TC_RAMCACHE
-    OFFON_SETTING(F_BANFROMQS,tagcache_ram,LANG_TAGCACHE_RAM,false,"tagcache_ram",NULL),
+    CHOICE_SETTING(F_BANFROMQS, tagcache_ram, LANG_TAGCACHE_RAM,
+                   0, "tagcache_ram", "off,on,quick",
+                   NULL, 3,
+                   ID2P(LANG_OFF), ID2P(LANG_ON), ID2P(LANG_QUICK_IGNORE_DIRACHE)),
 #endif
     OFFON_SETTING(F_BANFROMQS, tagcache_autoupdate, LANG_TAGCACHE_AUTOUPDATE, false,
                   "tagcache_autoupdate", NULL),

apps/tagcache.c

@@ -800,7 +800,8 @@ static long find_entry_ram(const char *filename)
     struct dircache_fileref dcfref;
 
     /* Check if tagcache is loaded into ram. */
-    if (!tc_stat.ramcache)
+    if (!tc_stat.ramcache
+        || global_settings.tagcache_ram != TAGCACHE_RAM_ON)
         return -1;
 
     if (dircache_search(DCS_CACHED_PATH | DCS_UPDATE_FILEREF, &dcfref,
@@ -5247,6 +5248,7 @@ static void tagcache_thread(void)
                 if (!tc_stat.ramcache && global_settings.tagcache_ram)
                 {
                     load_ramcache();
+                    if (global_settings.tagcache_ram == TAGCACHE_RAM_ON)
                         check_file_refs(global_settings.tagcache_autoupdate);
                     if (tc_stat.ramcache && global_settings.tagcache_autoupdate)
                         tagcache_build();

manual/rockbox_interface/tagcache.tex

@@ -52,10 +52,23 @@ with logging
     browsing but it does not use extra RAM and saves some battery on boot up. 
     
     \opt{HAVE_DISK_STORAGE}{
-    \note{If you browse your music frequently using the database, you should
+      If you browse your music frequently using the database, you should
       load to RAM, as this will reduce the overall battery consumption because
-      the disk will not need to spin on each search.}
+      the disk will not need to spin on each search.
     }
+
+    \note{When Load to RAM is turned on, and the directory cache is enabled as well,
+    it may take an unexpectedly long amount of time for disk activity to
+    wind down after booting, depending on your library size and player.
+
+    This can be mitigated by choosing the \setting{Quick} option instead, which causes
+    the database to ignore cached file references. In that case, you may notice brief
+    moments of disk activity once the path for a database entry has to be retrieved.
+
+    Set to \setting{On}, if you plan to take advantage the database's Update function,
+    or use a WPS that displays multiple upcoming tracks from the current playlist.
+    Otherwise, you may notice file names instead of metadata being displayed for those
+    tracks.}
   }
   
 \item[Auto Update]