Hi all,
I'm working on am335x-starter-kit with SDK ti-processor-sdk-linux-am335x-evm-02.00.02.11.
I have a question in GPMC_CONFIG7_i(where i is based on cs) BIT6, TRM says:
BIT6
Chip-select enable (reset value is 1 for CS[0] (active low) and 0 for
CS[1] to CS[5] (active low)).
0h = CS (active low) disabled
1h = CS (active low) enabled
It's seems that bit6 should always set to 1, thus enable CS, am I right?
The GPMC with net configura(GPMC_NET_CONF) in bootloader(./u-boot-2015.07+gitAUTOINC+46c915c963/arch/arm/include/asm/arch-omap3/mem.h)
also set the BIT6 to 1.
BUT
I try to write a "pseudo driver" which use ioremap to allocate a part of memory from GPMC memory, here is my pseudo code:
void __init pseudo_init(void)
{
/* GPMC config setting */
gpmc_cs_write_reg(GPMC_CS, GPMC_CS_CONFIG1, config[0]);
....
....
gpmc_cs_write_reg(GPMC_CS, GPMC_CS_CONFIG7, config[6]);
/* get gpmc cs request and get gpmc_memory base */
gpmc_cs_request(GPMC_CS, 16M, (unsigned long *)&gpmc_base);
if(err) exit;
/* here, print the gpmc_base address */
print(the gpmc_base address);
/* protect the part of memory */
request_mem_region(gpmc_base, 16M, "pseudo_mem");
/* now, mapping */
pseudo_base = ioremap(gpmc_base, 16M);
}
If the CONFIG7 bit6 = 1, the gpmc_base address = 0,
but if the CONFIG7 bit = 0, the gpmc_base = 0x10xxxxxx
if the CONFIG7 bit6 = 1, I CANNOT iowrite the pseudo_base(segmentation fault)
if the CONFIG7 bit6 = 0, I CAN iowrite the pseudo_base
Why?
ps: Actually, this is a pseudo driver which means no device on GPMC
