How to set SPI speed for ATmega1284P? I am using MightyCore and platformio. My config file looks like this
My fuses are set as:
E:FD 
H:D6 
L:8F

I have controller running at 16 MHz and SCK frequency is 8 MHz.
My display is showing white color and that is it. I know to make it function properly I have to use 1 MHz SPI clocking.
If I program CKDIV8 fuse my controller doesn't start. I dunno why, kind of black magic going on there for me. My lack of knowledge is not helpful there.
I tried to use the following tricks:
Setting SPI speed using TFT library
// earlier in main.cpp
Adafruit_ST7735 tft = Adafruit_ST7735(TFT_CS, TFT_DC, TFT_RST);
// later in setup()
tft.setSPISpeed(1000000); // has no effect on SCK

Trying to set it directly via SPI class instance:
// in setup()
SPI.setClockDivider(SPI_CLOCK_DIV128); // no effect

Or statically:
// in setup()
SPIClass::setClockDivider(SPI_CLOCK_DIV128); // still no effect

Also I tried to pass DEFAULT_SPI_FREQ build flag with frequency preset.
I ran out of ideas.
Schematic is here:
Per this issue setSPISpeed has to be made after initR like this:
tft.initR(INITR_BLACKTAB);
tft.setSPISpeed(1000000);