AM335x DDR3 Problem

Hi Kiyoji,

Did you do everything as described in these wikis: http://processors.wiki.ti.com/index.php/AM335x_EMIF_Configuration_tips and http://processors.wiki.ti.com/index.php/AM335x_DDR_PHY_register_configuration_for_DDR3_using_Software_Leveling

Here is a step-by-step tutorial how to do this: http://processors.wiki.ti.com/index.php/Sitara_Linux_Training:_Tuning_the_DDR3_Timings_on_BeagleBoneBlack

Hi Biser,

Yes I have already done these wiki. Writing 32bit value to 0x80000000～0x9FFFFFFC is fine. The problem is a byte writing.

After config_ddr() function, I executed a code below.

ulong ddata = 0;
writel(0x0, 0x80000000);
writeb(0x0, 0x80000000);
ddata = readl(0x80000000);

But ddata value is 0x00001200.  Why? It should be 0x0.

Now I am thinking of removing this DDR3 to change Micron device.

Best Regards,

Kiyoji 

I'm not a SW expert, but from what I see you write byte and read long. Can you try writing a more recognizable value, like 0xAA or 0x55?

Hi Biser,

OK I tried writing another vlue.

 ulong ddata_ul = 0;
 uchar ddata_uc0 = 0;
 uchar ddata_uc1 = 0;
 writel(0x0, 0x80000000);  // fill zero into address 0x80000000〜0x80000003
 writeb(0xAA, 0x80000000); // write 0xAA to address 0x80000000
 ddata_ul = readl(0x80000000);  // read from address 0x80000000. ddata_ul should be 0x000000AA.
 ddata_uc0 = readb(0x80000000);  // read from address 0x80000000. ddata_uc0 should be 0xAA.
 ddata_uc1 = readb(0x80000001);  // read from address 0x80000001. ddata_uc1 should be 0x00.
 printf("Test1 : ddata_ul=0x%x, ddata_uc0=0x%x, ddata_uc1=0x%x\n", (unsigned int)ddata_ul, (unsigned int)ddata_uc0, (unsigned int)ddata_uc1);
 
 writel(0x0, 0x80000000);  // fill zero into address 0x80000000〜0x80000003
 writeb(0x55, 0x80000000); // write 0x55 to address 0x80000000
 ddata_ul = readl(0x80000000);  // read from address 0x80000000. ddata_ul should be 0x00000055.
 ddata_uc0 = readb(0x80000000);  // read from address 0x80000000. ddata_uc0 should be 0x55.
 ddata_uc1 = readb(0x80000001);  // read from address 0x80000001. ddata_uc1 should be 0x00.
 printf("Test2 : ddata_ul=0x%x, ddata_uc0=0x%x, ddata_uc1=0x%x\n", (unsigned int)ddata_ul, (unsigned int)ddata_uc0, (unsigned int)ddata_uc1);
 
 writel(0x123455aa, 0x80000000);  // write 0x123455AA to address 0x80000000
 ddata_ul = readl(0x80000000);  // read from address 0x80000000. ddata_ul should be 0x123455AA.
 ddata_uc0 = readb(0x80000000);  // read from address 0x80000000. ddata_uc0 should be 0xAA.
 ddata_uc1 = readb(0x80000001);  // read from address 0x80000001. ddata_uc1 should be 0x55.
 printf("Test3 : ddata_ul=0x%x, ddata_uc0=0x%x, ddata_uc1=0x%x\n", (unsigned int)ddata_ul, (unsigned int)ddata_uc0, (unsigned int)ddata_uc1); 

Result is

Test1 : ddata_ul=0x1200, ddata_uc0=0x0, ddata_uc1=0x12
Test2 : ddata_ul=0xed00, ddata_uc0=0x0, ddata_uc1=0xed
Test3 : ddata_ul=0x123455aa, ddata_uc0=0xaa, ddata_uc1=0x55  

Good result is only test3 on our custom board. Same test on BBB was all good.

Best regards,

Kiyoji

Can you boot to u-boot prompt?

This probably means that DDR is not working properly. This can be due either to a schematic error, bad PCB layout, bad PCB assembly, or wrong DDR configuration. I suggest you follow the step-by-step tutorial I referred above to eliminate the possibility of wrong DDR configuration.