Issue with dcahe enabling.

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Hi,

 

I'm doing kernel porting to arm926 based FPGA board, very minimal setup.

Only UART and timer devices are available as part of FPGA.

 

 

Board details –

 

Using ARM926e-js processor with 128MB SDRAM., Clock-33Mhz

SDRAM Size = 128M                  

 

CONFIG_PAGE_OFFSET = 0xc0000000

CONFIG_PHYS_OFFSET= 0x80000000

 

Kernel Lowmem = 32M including 8M for initramfs (starting from  24M to 32M).

HighMEM is not configured.

 

Vmalloc_start =     end address of LowMem (i.e 0xC200000)

VMALLOC_END =  Vmalloc_start + 64M  = 0xC6000000

 

If I enable data cache and debug with JTAG, Kernel ends up in ENTRY(__delay).

This is due to the corruption of the “meminfo” structure.

 

I could also observe during step by step using trace32 , after excuting few instructions that modifies memory(refer label), the data in that particular memory is not modify.

Because of which there is corruption of the meminfo structure ending up in looping in  “ setup_arch -->paging_init --> prepare_page_table”.

 

Label:

The instructions that should actually  modify memory, but the memory is not modified are from parse_early_param() --> parse_early_options --> parse_args --> next_arg -->

 

for (i = 0; args[i]; i++) {

                if (isspace(args[i]) && !in_quote)

                        break;

                if (equals == 0) {

                        if (args[i] == '=')

                                equals = i;

                }

                if (args[i] == '"')

                        in_quote = !in_quote;

        }

 

        *param = args;

        if (!equals)

                *val = NULL;

        else {

                args[equals] = '\0';

 

 

which modifies the command line args passed. The instruction that sets the ‘=’ location to ‘NULL’ as highlighted is not modifying the memory .

 

Please let me know how dcahe enabling is creating this effect.,as with dcache disabled(CPU_DCACHE_DISABLE = y)  this instruction is replacing the ‘=’ symbol with NULL.

 

 Karthik.

 

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