The time taken from POR to when the display comes up is noted to be approximately 180ms. The measurement was taken by using a GPIO pin, which by default is in active-low state. The pin is set high in CSL_dssVpSetGoBit() by using the gpio_set_high() API. OSPI NOR is used as boot-media for testing purposes.

• The dss_display share example provided in the default MCU+ SDK is used for experimentation. Modifications to this example are made to implement the flicker-free transition demonstrated through SBL flow.
• GPIO0_39 on the user expansion connector-pin 18, is used for time measurements. Figure 5-5 shows the options in SysConfig to enable this pin:
  Figure 5-5 SysConfig Settings
• Set the GPIO pin to high by defining the API in dss_display_share.c as follows :

  void gpio_set_high(void *args) { 
  	uint32_t gpioBaseAddr, pinNum;
  	DebugP_log("GPIO LED started ...\r\n");
  	
  	/* Get address after translation translate */ 
  	gpioBaseAddr = (uint32_t) AddrTranslateP_getLocalAddr(GPIO_LED_BASE_ADDR); pinNum = GPIO_LED_PIN;
  	GPIO_setDirMode(gpioBaseAddr, pinNum, GPIO_LED_DIR);
  	GPIO_pinWriteHigh(gpioBaseAddr, pinNum);
  	DebugP_log("GPIO LED HIGH!!\r\n");
  }

• Use the API in CSL_dssVpSetGoBit() as follows:

  diff --git a/source/drivers/dss/v0/hw_include/V3/csl_dssVideoPort.c b/source/drivers/dss/v0/hw_include/V3/csl_dssVideoPort.c
  
  index f882d54..ee18b95 100755
  
  --- a/source/drivers/dss/v0/hw_include/V3/csl_dssVideoPort.c
  
  +++ b/source/drivers/dss/v0/hw_include/V3/csl_dssVideoPort.c
  
  @@ -183,6 +183,8 @@ void CSL_dssVpEnable(CSL_dss_vpRegs *vpRegs, uint32_t enable)
  
       CSL_REG32_WR(&vpRegs->CONTROL, regVal);
  
   }
  
  +extern void gpio_set_high(void *args);
  
  +
  
   void CSL_dssVpSetGoBit(CSL_dss_vpRegs *vpRegs)
  
   {
  
       uint32_t regVal;
  
  @@ -192,6 +194,7 @@ void CSL_dssVpSetGoBit(CSL_dss_vpRegs *vpRegs)
  
                DSS_VP1_CONTROL_GOBIT,
  
                CSL_DSS_VP1_CONTROL_GOBIT_VAL_UFPSR);
  
       CSL_REG32_WR(&vpRegs->CONTROL, regVal);
  
  +    gpio_set_high(NULL);
  
   }
  
   void CSL_dssVpSetLcdTdmConfig(CSL_dss_vpRegs *vpRegs,

• When the GPIO0_39 pin is connected to the logic analyzer, the GPIO pin is set high at around 180ms.