Optimize lcd-ssd1303 driver (clip series)

Saves 100+ bytes (50 of it in iram), saves a bit of power

Internal LCD clock decreased but with added efficiency of drawing routines
loses only around 2 Hz on the scanrate (~75Hz) while fps is slightly increased

Column offsets are now calculated outside the loops saving a few instructions

Passing a LCD_NOP command after lcd_update turns off Data/Cmd# gpio
saving a bit more power

Added a function lcd_write_cmd_triple() that allows 3 commands to be sent at once
when enabled with LCD_USE_FIFO_FOR_COMMANDS it sends them back to back without
checking FIFO status in between or sending to thhe D/C# Gpio.
Makes an assumption about the FIFO being large enough to
accept 3 commands after being emptied which should be the case on the
clipv1, clipv2, clipplus. I have only enabled it for the clip plus
as thats the only device I have to test it on.

On clip+ the SSP clock is now turned off when screen is off

Change-Id: Ib5fd24697bfe4ac8b8ee017361e789e4a7910d21

1 files changed, 29 insertions, 0 deletions

diff --git a/firmware/target/arm/as3525/sansa-clipv2/lcd-clipv2.c b/firmware/target/arm/as3525/sansa-clipv2/lcd-clipv2.c
index d7266f72a0..0b3317255a 100644
--- a/firmware/target/arm/as3525/sansa-clipv2/lcd-clipv2.c
+++ b/firmware/target/arm/as3525/sansa-clipv2/lcd-clipv2.c
@@ -63,6 +63,35 @@ void lcd_write_command(int byte)
     DBOP_TIMPOL_23 = 0xE037E037;
 }
 
+void lcd_write_cmd_triplet(int cmd1, int cmd2, int cmd3)
+{
+#ifndef LCD_USE_FIFO_FOR_COMMANDS
+    lcd_write_command(cmd1);
+    lcd_write_command(cmd2);
+    lcd_write_command(cmd3);
+#else
+    /* combine writes to data register */
+
+    while ((DBOP_STAT & (1<<10)) == 0) /* While push fifo is not empty */
+        ;
+    /* FIFO is empty at this point */
+    /* unset D/C# (data or command) */
+    GPIOB_PIN(2) = 0;
+    DBOP_TIMPOL_23 = 0xE0370036;
+
+    /* Write command */
+    /* !!makes assumption FIFO is at least (3) levels deep! */
+    DBOP_DOUT8 = cmd1;
+    DBOP_DOUT8 = cmd2;
+    DBOP_DOUT8 = cmd3;
+    /* While push fifo is not empty */
+    while ((DBOP_STAT & (1<<10)) == 0)
+        ;
+
+    DBOP_TIMPOL_23 = 0xE037E037;
+#endif
+}
+
 void lcd_write_data(const fb_data* p_bytes, int count)
 {
     volatile int i = 0;