Re: How to use mpc8xxx_gpio.c device driver

[Ravi Gupta <dceravigupta@gmail.com>]

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On Wed, Aug 11, 2010 at 9:45 PM, MJ embd <mj.embd@gmail.com> wrote:

> u can directly access GPIO registers in kernel, by ioremap of GPIO
> memory mapped registers.
> you might need to check
> - muxing of gpio
>
> -mj
>

Hi MJ,

Thanks for the reply.
I tried memory mapping but it fails, here is my code :

#include <linux/module.h>
#include <linux/errno.h>    /* error codes */
#include <linux/mm.h>

void __iomem *ioaddr = NULL;

static __init int sample_module_init(void)
{
    ioaddr = ioremap(0xFF400C00, 0x24);
    if(ioaddr == NULL) {
        printk(KERN_WARNING "ioremap failed\n");
    }
    printk(KERN_WARNING "ioremap successed\n");
    printk(KERN_WARNING "GP1DIR = %u\n", ioread32(ioaddr));
    return 0;
}

static __exit void sample_module_exit(void)
{
    iounmap(ioaddr);
}

MODULE_LICENSE("GPL");
module_init(sample_module_init);
module_exit(sample_module_exit);

As per the MPC8377ERDB data sheet default IMMRBAR address is 0xFF40_0000 and
offset of GPIO1 is 0C00 and each GPIO has programmable registers that occupy
24 bytes of memory-mapped space, so I mapped from 24bytes (0x18) starting
from 0xFF40_0C00 address. But when I tried to read the values from the
mapped memory I get the following errors. Is there something I am missing.
Any help with reference to MPC8377ERDB board will be highly appreciable.

# tftp -l ~/immrbar.ko -r immrbar.ko -g 10.20.50.70
# insmod ./immrbar.ko
[  717.825241] ioremap successed
[  717.849215] Machine check in kernel mode.
[  717.853220] Caused by (from SRR1=41000): Transfer error ack signal
[  717.859405] Oops: Machine check, sig: 7 [#1]
[  717.863668] MPC837x RDB
[  717.866106] Modules linked in: immrbar(+)
[  717.870119] NIP: 00000900 LR: d1034054 CTR: c0014d50
[  717.875079] REGS: cf895d00 TRAP: 0200   Not tainted  (2.6.28.9)
[  717.880992] MSR: 00041000 <ME>  CR: 24000082  XER: 20000000
[  717.886578] TASK = cf8e8640[647] 'insmod' THREAD: cf894000
[  717.891882] GPR00: d103404c cf895db0 cf8e8640 00000000 000023d5 ffffffff
c01e
04f4 00020000
[  717.900265] GPR08: 00000001 c0383f3c 000023d5 c0014d50 4c72ff56 10019100
1007
77e0 1007ea98
[  717.908650] GPR16: 10077834 100a0000 100a0000 100a0000 bfaf4828 00000000
1009
f23c 10000cfc
[  717.917034] GPR24: 10000d00 10000d24 10012008 c03650e8 00000000 d1034000
1001
2018 d1030000
[  717.925598] NIP [00000900] 0x900
[  717.928828] LR [d1034054] sample_module_init+0x54/0xc0 [immrbar]
[  717.934828] Call Trace:
[  717.937273] [cf895db0] [d103404c] sample_module_init+0x4c/0xc0 [immrbar]
(unr
eliable)
[  717.945115] [cf895dc0] [c00038a0] do_one_initcall+0x64/0x18c
[  717.950780] [cf895f20] [c004d7b8] sys_init_module+0xac/0x19c
[  717.956441] [cf895f40] [c00122f0] ret_from_syscall+0x0/0x38
[  717.962013] --- Exception: c01 at 0x48043f6c
[  717.962017]     LR = 0x100009cc
[  717.969407] Instruction dump:
[  717.972370] 00000000 XXXXXXXX XXXXXXXX XXXXXXXX 00000000 XXXXXXXX
XXXXXXXX XX
XXXXXX
[  717.980140] 00000000 XXXXXXXX XXXXXXXX XXXXXXXX 7d5043a6 XXXXXXXX
XXXXXXXX XX
XXXXXX
[  717.987919] ---[ end trace a47be794e2873cef ]---

Thanks in advance
Ravi Gupta

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