CCS/TMS320F28335: TFT-LCD control using SPI module

Tool/software: Code Composer Studio

Hi, I was trying to control my TFT-LCD by using hardware SPI. While using software SPI, LCD can dsiplay with nothing wrong.

The only difference in my code between them is that if #define USE_HARDWARE_SPI, the WriteData function will use SPI module or it will use software SPI.

Here's my code about SPI configuration, actually I referred to the example code:

void SPI_Init(void){
    InitSpiaGpio();
    SpiaRegs.SPIFFTX.all=0xE040;
    SpiaRegs.SPIFFRX.all=0x204f;
    SpiaRegs.SPIFFCT.all=0x0;                //delay=0
    SpiaRegs.SPICCR.all =0x0007;                 // Reset on, rising edge, 8-bit char bits
    SpiaRegs.SPICTL.all =0x0006;                 // Enable master mode, normal phase,
                                                     // enable talk, and SPI int disabled.
    SpiaRegs.SPIBRR =0x007F;
    SpiaRegs.SPICCR.all =0x0087;                 // Relinquish SPI from Reset
    SpiaRegs.SPIPRI.bit.FREE = 1;                // Set so breakpoints don't disturb xmission
}

void SPI_WriteData_Hardware(unsigned char Data){
    Uint16 temp,clear;
    temp=Data;
    SpiaRegs.SPITXBUF=(temp<<8);
    while(SpiaRegs.SPIFFRX.bit.RXFFST !=1) { }
    clear=SpiaRegs.SPIRXBUF;
}

The problem is that when I build the project, ccs will give a warning:

variable "clear" was set but never used.

In fact, when I run it step by step, the program can run the last step in function SPI_WriteData_Hardware. But the lcd still cannot display. I thought SPI maybe where the problem is.

Could you help me? Thanks so much.