[U-Boot] valid RAM region on a 256MB fails occasionally

[harsha kiran]

Hi !

I am trying to run a u-boot.bin from the RAM as a standalone application and
occationally my board hangs and resets. i found the place it breaks but dont
have any clue why..

After the u-boot.img is loaded, i get the cmd prompt and run run the
u-boot.bin from by boot partition of emmc
U-Boot# fatload mmc 1:1 0x84000000 u-boot.bin
reading u-boot.bin
388959 bytes read in 44 ms (8.4 MiB/s)
U-Boot# go 0x84000000
## Starting application at 0x84000000 ...

Here the u-boot.bin starts and runs fine most of the time. occationally i
get the following and system hangs and resets. 

RAM Configuration:
Bank #0: 80000000
DRAM:  1 GiB

I have a 256M lpDDR Ram on our custom board and for some reason u-boot
calculates the wrong (1Gb) on the bad cases..

Here is the file it reports the calculated RAM size..
u-boot-2015.07/common/memsize.c.

I added some debug prints and here are the outputs for a valid case and
occational bad reset..


function modified:
---------------------

long get_ram_size(long *base, long maxsize)
{
	volatile long *addr;
	long           save[32];
	long           cnt;
	long           val;
	long           size;
	int            i = 0;

	printf("The value of base is %ld and max value is %ld and size of long is
%d \n", *base, maxsize, sizeof(long));


	for (cnt = (maxsize / sizeof(long)) >> 1; cnt > 0; cnt >>= 1) {
		addr = base + cnt;	/* pointer arith! */
		printf("address= %ld ", *addr);
		sync();
		save[i++] = *addr;
		printf("save[%d]=%ld \n", i, *addr);
		sync();
		*addr = ~cnt;
	}
  printf("The address val is %ld ", *addr);
	addr = base;
	sync();
	save[i] = *addr;
	sync();
	*addr = 0;
	printf("save[%d]=%ld \n", i, *addr);
	sync();
	if ((val = *addr) != 0) {
		/* Restore the original data before leaving the function. */
	  puts(" The value of addr is 0 \n");
		sync();
		*addr = save[i];
		for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
			addr  = base + cnt;
			sync();
			*addr = save[--i];
		}
		puts("Returning zero size !!!");
		return (0);
	}

	for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
		addr = base + cnt;	/* pointer arith! */
		val = *addr;
		*addr = save[--i];

		printf("base=%ld , val=%ld ,  address,save[%d]=%ld, cnt=%ld and ~cnt=%ld
\n",*base, val,i,*addr,cnt,~cnt);

		if (val != ~cnt) {
			size = cnt * sizeof(long);

			printf("calulated size is  %ld \n!!!!", size);
			/*
			 * Restore the original data
			 * before leaving the function.
			 */
			for (cnt <<= 1;
			     cnt < maxsize / sizeof(long);
			     cnt <<= 1) {
				addr  = base + cnt;
				*addr = save[--i];
			}

		  printf("returning cal size %ld \n!!!!", size);
			return (size);
		}
	}

	puts("returning max size!!!!");
	return (maxsize);
}


Bad Case:
----------------
<http://u-boot.10912.n7.nabble.com/file/n226040/bad.jpg> 

Good Case:
--------------

<http://u-boot.10912.n7.nabble.com/file/n226040/good.jpg> 


I get a value even after the valid RAM range and this happens randomly..
I have caches enabled in both the u-boot.img and u-boot.bin. please let me
know if i am missing anything..

Thanks,
Harsha





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