Trigger a burst operation on GPMC

Jun Ma81458

Other Parts Discussed in Thread: AM3715

Hi,

I am working with AM3715, and a FPGA is connected to processor on GPMC bus, on synchronous burst mode. As a hardware guy, I using u-boot instead of real linux to verify the communication between CPU and FPGA.

I found that the mw.l and md.l command of u-boot can only trigger a burst operation with burst length = 2. Some topic (http://e2e.ti.com/support/dsp/omap_applications_processors/f/447/t/36314.aspx) in E2E forum has mentioned using u64 pointer can trigger 4-word burst, but I still measured 2 consecutive burst operations, each burst length is 2. I have set up the GPMC register, and following are my codes. Can any one give me some ideas about how to trigger a 4-word burst in U-Boot (Non-DMA mode)?

Regards,

Jun Ma

---------------------------------------------------------------------------------

/*
* GPMC configuration for FPGA-CPU communication
* based on CORE_L3_ICLK = GPMC_FCLK = 200MHz
*/
#define FPGA_ACCESS_GPMC_CONFIG1 0x7d671202
#define FPGA_ACCESS_GPMC_CONFIG2 0x000a0d00
#define FPGA_ACCESS_GPMC_CONFIG3 0x00030300
#define FPGA_ACCESS_GPMC_CONFIG4 0x03000d05
#define FPGA_ACCESS_GPMC_CONFIG5 0x030b0b0e
#define FPGA_ACCESS_GPMC_CONFIG6 0x88050384
#define FPGA_ACCESS_GPMC_CONFIG7 0x00000f60

---------------------------------------------------------------------------------

/* Trigger a burst READ (LEN = 4) to FPGA on GPMC bus */
void fpga_reg_access_test(void)
{
u64* pVal;
u64* ptr = (u64*)(CONFIG_FPGA_COMM_BASE);
u32 a, b;

pVal = (u64*)malloc(sizeof(u64));

*pVal = *ptr;

a = (u32)(*pVal);
b = (u32)((*pVal) >> 32);

printf("Read FPGA reg value: 0x%08x 0x%08x\n", b, a);

}

---------------------------------------------------------------------------------

over 12 years ago

0 Renjith Thomas over 12 years ago

Guru 31670 points

Jun,

You've to write ARM assembly to achieve the same. You can do upto 32 or even 40 bytes of burst on GPMC. This depends on how you write the code. But a minimum of 32 is possible.

0 Jun Ma81458 over 12 years ago in reply to Renjith Thomas

Prodigy 80 points

Hi Tomas,

Thanks for your suggestion! I create a simple function with asm code. Unfortunately, the processor is stopped after execute the asm instructions of this function. As I am a HW guy and have limit knowledge about Cortex A8 assembly language, could you take a look at my code?

Regards,

Jun

void fpga_burst_test(void)
{
u32* pVal;
volatile u32* ptr = (u32*)(CONFIG_FPGA_COMM_BASE + 0x10);
u16 i;
volatile u16* pa;

pVal = (u32*)malloc(8*sizeof(u32));

asm volatile(
   "ldmia %[in]!, {r3-r10} \n\t"
   "stmia %[out]!, {r3-r10} \n\t"
   :[out]"+r" (pVal)
   :[in]"r" (ptr)
   :"r3","r4","r5","r6","r7","r8","r9","r10","memory"
      );

pa = (u16*)pVal;

printf("FPGA burst test:\n");
for(i = 0; i < 16; i ++) {
printf("Read FPGA reg value: 0x%08x \n", *pa);
pa++;
}

free(pVal);

}

0 Renjith Thomas over 12 years ago in reply to Jun Ma81458

Guru 31670 points

Jun,

The problem with your code is that you are allocating the registers directly. Basically you've to let the compiler allocate registers for you. You can follow this http://www.ethernut.de/en/documents/arm-inline-asm.html

0 Jun Ma81458 over 12 years ago in reply to Renjith Thomas

Prodigy 80 points

Hi Renjith,

I read the cookbook you suggested, but I don't find the section about how to make the compiler allocate registers. Could show me which section is about this topic?

I know I asked for too much... If you have time...

Regards,
Jun

0 Renjith Thomas over 12 years ago in reply to Jun Ma81458

Guru 31670 points

Jun,

If you write code like this compiler will allocate it for you.

asm volatile("ldr %0, [%1]"     "\n\t"
             "str %2, [%1, #4]" "\n\t" 
             : "=&r" (rdv) 
             : "r" (&table), "r" (wdv)
             : "memory");

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Trigger a burst operation on GPMC