drivers/lcd/st7789: add option for SPI delay control

It is now possible to configure SPI delays for st7789 controller if
CONFIG_SPI_DELAY_CONTROL is set. Default values for SPI peripheral
may be too long or too short, therefore the display controller set
its own values as required. The default values in configuration
are taken from the reference manual, but it is possible they may
require tuning for different revisions or temperatures for
example.

Signed-off-by: Michal Lenc <michallenc@seznam.cz>

drivers/lcd/Kconfig

@@ -783,6 +783,38 @@ config LCD_ST7789_FREQUENCY
 	int "SPI Frequency"
 	default 1000000
 
+config LCD_ST7789_START_DELAY
+	int "ST7789 SPI start delay"
+	depends on SPI_DELAY_CONTROL
+	range 0 1000000
+	default 60
+	---help---
+		The delay between CS active and first CLK. In ns.
+
+config LCD_ST7789_STOP_DELAY
+	int "ST7789 SPI stop delay"
+	depends on SPI_DELAY_CONTROL
+	range 0 1000000
+	default 65
+	---help---
+		The delay between last CLK and CS inactive. In ns.
+
+config LCD_ST7789_CS_DELAY
+	int "ST7789 SPI chip select delay"
+	depends on SPI_DELAY_CONTROL
+	range 0 1000000
+	default 40
+	---help---
+		The delay between CS inactive and CS active again. In ns.
+
+config LCD_ST7789_IFDELAY
+	int "ST7789 SPI frames delay"
+	depends on SPI_DELAY_CONTROL
+	range 0 1000000
+	default 50
+	---help---
+		The delay between consecutive frames. In ns.
+
 endif # LCD_ST7789
 
 config LCD_GC9A01

drivers/lcd/st7789.c

@@ -315,6 +315,11 @@ static void st7789_select(FAR struct spi_dev_s *spi, int bits)
   SPI_SETMODE(spi, CONFIG_LCD_ST7789_SPIMODE);
   SPI_SETBITS(spi, bits);
   SPI_SETFREQUENCY(spi, CONFIG_LCD_ST7789_FREQUENCY);
+#ifdef CONFIG_SPI_DELAY_CONTROL
+  SPI_SETDELAY(spi, CONFIG_LCD_ST7789_START_DELAY,
+               CONFIG_LCD_ST7789_STOP_DELAY, CONFIG_LCD_ST7789_CS_DELAY,
+               CONFIG_LCD_ST7789_IFDELAY);
+#endif
 }
 
 /****************************************************************************