Sansa Clip Zip: Implement LCD flip (180 degree rotation)

Enable HAVE_LCD_FLIP for the Clip Zip and implement lcd_set_flip()
in the LCD driver, making the Display -> Flip Display setting work.
This lets the player be used upside down, e.g. clipped to clothing
with the control buttons pointing up and screen on the bottom.

Defining HAVE_LCD_FLIP also activates the existing button remap in
button_flip() (firmware/drivers/button.c) for this target: while the
display is flipped, LEFT/RIGHT, UP/DOWN and the volume keys are all
swapped to match the new orientation, so the whole device is usable
upside down, not just readable.

The flip is done in hardware by reversing the controller's GRAM write
direction and mirroring the write window in lcd_setup_rect, so partial
updates keep working and there is no per-frame cost. Both panel
variants are handled: the type 0 WiseChip/SEPS114A via MEMORY_WRITE/READ
(1Dh, 0x02), and the type 1 Visionox/LD7134 via the Graphic RAM Writing
Direction register (05h, 0x03). The direction register is written in
lcd_enable(), so it is set while the panel is powered and is re-applied
after display standby; lcd_set_flip() cycles the panel off and on so a
change to the setting takes effect immediately.

For the simulator, which has no real LCD controller, lcd_set_flip() is
implemented in the SDL LCD driver (lcd-bitmap.c) as a software mirror of
the framebuffer, so the flip is visible in theme previews; the generic
uisimulator stub is guarded out when HAVE_LCD_FLIP is defined.

Tested on real type 1 / LD7134 hardware in both orientations: display
content, button remapping and album art are all correct, and test_fps
shows partial updates run at full speed when flipped (1/4 frame 325 fps,
matching the non-flipped rate). The type 0 / SEPS114A path uses the same
approach; the 0x02 direction value was confirmed to flip a type 0 panel
by William Wilgus during review.

Change-Id: I99ef13949102b344826e72d1d90c71e2271448a6

docs/CREDITS

@@ -761,6 +761,7 @@ Javier Gutiérrez Gertrúdix
 Sergey Puskov
 Eivind Ødegård
 Teun van Dalen
+Adam N. Burke
 
 The libmad team
 The wavpack team

firmware/drivers/button.c

@@ -459,7 +459,6 @@ static int button_flip(int button)
 {
     int newbutton = button;
 
-#if (CONFIG_PLATFORM & PLATFORM_NATIVE)
     newbutton &= ~(
 #if defined(BUTTON_LEFT) && defined(BUTTON_RIGHT)
         BUTTON_LEFT | BUTTON_RIGHT
@@ -521,7 +520,6 @@ static int button_flip(int button)
     if (button & BUTTON_PREV)
         newbutton |= BUTTON_NEXT;
 #endif
-#endif /* !SIMULATOR */
     return newbutton;
 }
 

firmware/export/config/sansaclipzip.h

@@ -76,7 +76,7 @@
 #endif
 
 /* define this if you can flip your LCD */
-//#define HAVE_LCD_FLIP
+#define HAVE_LCD_FLIP
 
 /* define this if you can invert the pixels */
 //#define HAVE_LCD_INVERT

firmware/target/arm/as3525/sansa-clipzip/lcd-clipzip.c

@@ -29,6 +29,10 @@
 /* the detected lcd type (0 or 1) */
 static int lcd_type;
 
+/* set by lcd_set_flip(): when true the panel is rotated 180 degrees via the
+   controller's GRAM write direction (see lcd_set_flip and lcd_setup_rect) */
+static bool lcd_flipped = false;
+
 #ifdef HAVE_LCD_ENABLE
 /* whether the lcd is currently enabled or not */
 static bool lcd_enabled;
@@ -274,6 +278,10 @@ void lcd_enable(bool on)
             sleep(HZ * 100/1000);
 
             lcd_write(0xD0, 0x00);  /* SCREEN_SAVER_CONTROL */
+
+            /* apply 180 degree flip via memory write direction (1Dh):
+               MDIR1|MDIR0 = decrement both; normal is horizontal-decrement */
+            lcd_write(0x1D, lcd_flipped ? 0x02 : 0x01);
         }
         else {
             lcd_write(0xD2, 0x05);
@@ -290,6 +298,10 @@ void lcd_enable(bool on)
             lcd_write(0x03, 0x00);
 
             lcd_write(0x02, 0x01);
+
+            /* apply 180 degree flip via graphic RAM writing direction (05h):
+               D[2:0] = 011 starts from XE,YE (both axes reversed) */
+            lcd_write(0x05, lcd_flipped ? 0x03 : 0x00);
         }
         else {
             lcd_write(0x02, 0x00);
@@ -297,7 +309,7 @@ void lcd_enable(bool on)
             lcd_write(0x03, 0x01);
         }
     }
-    
+
     lcd_enabled = on;
 }
 
@@ -324,6 +336,18 @@ void lcd_init_device(void)
 /* sets up the lcd to receive frame buffer data */
 static void lcd_setup_rect(int x, int x_end, int y, int y_end)
 {
+    if (lcd_flipped) {
+        /* Mirror the window to the opposite corner; the reversed write
+           direction set in lcd_enable() fills it back-to-front, drawing the
+           framebuffer rotated 180 degrees with no per-pixel work. */
+        int fx = LCD_WIDTH  - 1 - x_end;
+        int fy = LCD_HEIGHT - 1 - y_end;
+        x_end  = LCD_WIDTH  - 1 - x;
+        y_end  = LCD_HEIGHT - 1 - y;
+        x = fx;
+        y = fy;
+    }
+
     if (lcd_type == 0) {
         lcd_write(0x34, x);     /* MEM_X1 */
         lcd_write(0x35, x_end); /* MEM_X2 */
@@ -380,6 +404,23 @@ void lcd_write_data(const fb_data *data, int count)
     }
 }
 
+/* Rotate the display 180 degrees (the flip_display setting). Both panel
+   controllers do this in hardware by reversing the GRAM write direction (set in
+   lcd_enable) so the address counter walks the framebuffer backwards;
+   lcd_setup_rect mirrors the write window to match. Cycle the panel off/on here
+   so a change (e.g. toggled from the menu) takes effect immediately. */
+void lcd_set_flip(bool yesno)
+{
+    if (yesno == lcd_flipped)
+        return;
+    lcd_flipped = yesno;
+
+    if (lcd_enabled) {
+        lcd_enable(false);
+        lcd_enable(true);
+    }
+}
+
 /* Updates a fraction of the display. */
 void lcd_update_rect(int x, int y, int width, int height)
 {
@@ -392,7 +433,7 @@ void lcd_update_rect(int x, int y, int width, int height)
         /* rectangle is outside visible display, do nothing */
         return;
     }
-    
+
     /* update entire horizontal strip for display type 0 (wisechip) */
     if (lcd_type == 0) {
         x = 0;

firmware/target/hosted/sdl/lcd-bitmap.c

@@ -113,6 +113,17 @@ static unsigned long get_lcd_pixel(int x, int y)
 #endif
 }
 
+#ifdef HAVE_LCD_FLIP
+/* The simulator has no real LCD controller, so flip_display is done in software
+   here: when set, the framebuffer is mirrored as it is copied to the surface.
+   (On the device the controller flips itself; see lcd-clipzip.c.) */
+static bool sim_lcd_flipped = false;
+void lcd_set_flip(bool yesno)
+{
+    sim_lcd_flipped = yesno;
+}
+#endif
+
 void lcd_update(void)
 {
     /* update a full screen rect */
@@ -121,6 +132,29 @@ void lcd_update(void)
 
 void lcd_update_rect(int x_start, int y_start, int width, int height)
 {
+#ifdef HAVE_LCD_FLIP
+    if (sim_lcd_flipped)
+    {
+        /* redraw the whole panel mirrored in both axes (sim software flip) */
+        SDL_Rect d = {0, 0, 1, 1};
+        int x, y;
+        for (y = 0; y < LCD_HEIGHT; y++)
+        {
+            for (x = 0; x < LCD_WIDTH; x++)
+            {
+                d.x = x;
+                d.y = y;
+                SDL_FillRect(lcd_surface, &d, (Uint32)
+                    get_lcd_pixel(LCD_WIDTH - 1 - x, LCD_HEIGHT - 1 - y));
+            }
+        }
+        sdl_gui_update(lcd_surface, 0, 0, LCD_WIDTH,
+                       LCD_HEIGHT + LCD_SPLIT_LINES, SIM_LCD_WIDTH, SIM_LCD_HEIGHT,
+                       background ? UI_LCD_POSX : 0, background? UI_LCD_POSY : 0);
+        return;
+    }
+#endif
+
     sdl_update_rect(lcd_surface, x_start, y_start, width, height,
                     LCD_WIDTH, LCD_HEIGHT, get_lcd_pixel);
     sdl_gui_update(lcd_surface, x_start, y_start, width,

uisimulator/common/lcd-common.c

@@ -37,10 +37,12 @@ static bool lcd_enabled = false;
 static bool lcd_sleeping = true;
 #endif
 
+#if !defined(HAVE_LCD_FLIP)
 void lcd_set_flip(bool yesno)
 {
     (void)yesno;
 }
+#endif
 
 void lcd_set_invert_display(bool invert)
 {