Linux/AM3352: Use pin mcasp0_aclkx to generate clock

Phil Chang

Intellectual 580 points

Part Number: AM3352

Tool/software: Linux

Hi all,

Our custom board have no audio on it, therefore I didn't use mcasp diver on it.

But our buzzer is connect to pin(V16) to generate signal driving the buzzer,

The buzzer need to get clock signal(high->low->high->low), so I think I can use pin(V16) as mcasp0_aclkx ti generate clock signal,

I wrote a module(.ko) to configure this pin:

#define BASE    0x46000000
#define SIZE    0x400000 //4Mb
#define ACLKX   0xb0

static int test_init(void)
{
    u32 reg;

    printk("buzzer start!\n");

    if(!request_mem_region(BASE, SIZE, "buzzer")){
        pr_err("request_mem_region failed!\n");
        return -1;
    }

    pr_info("request_mem_region success!\n");

    base = ioremap_nocache(BASE, SIZE);                                                                                                             
    if(base == NULL){
        pr_err("ioremap failed!\n");
        return -1;
    }

    pr_info("ioremap_success!\n");

//  __raw_write(BIT(5)|BIT(7), base+ACLKX);

    reg = __raw_read(base);

    pr_info("reg = %lx\n", reg);

    return 0;
}

but dead in __raw_read(reg):

Unhandled fault: external abort on non-linefetch (0x1028) at 0xd1000000

...

Is mcasp0 base address 0x46000000 ? or I need to use hole mcasp driver?

over 8 years ago

0 Phil Chang over 8 years ago

Intellectual 580 points

It's seems I need to enable some clock or power thus read the mcasp register, but I don't know which is I need to open, is anyone could tell me?

0 Cvetolin Shulev-XID over 8 years ago in reply to Phil Chang

TI__Guru 65405 points

Hi Phil,

I suggest you to refer to am335x TRM McASP section to check the registers configuration.
www.ti.com/.../spruh73p.pdf

BR
Tsvetolin Shulev

0 Phil Chang over 8 years ago in reply to Cvetolin Shulev-XID

Intellectual 580 points

Thanks for reply
In trm, the McASP0 CFG physical address should be 0x4803_8000, and size should be 8kb

ref: Table 2-3. L4_PER Peripheral Memory Map (continued)

thus. my code should modify like this:

#define BASE 0x48038000
#define SIZE SIZE_8K
#define ACLKX 0xb0

static int test_init(void)
{
u32 reg;

printk("buzzer start!\n");

if(!request_mem_region(BASE, SIZE, "buzzer")){
pr_err("request_mem_region failed!\n");
return -1;
}

pr_info("request_mem_region success!\n");

base = ioremap_nocache(BASE, SIZE);
if(base == NULL){
pr_err("ioremap failed!\n");
return -1;
}

pr_info("ioremap_success!\n");

reg = __raw_read(base); // read the revision number

pr_info("reg = %lx\n", reg);

return 0;
}

In trm, offset 0x0h is Revision Identification Register, But I still cannot read it!
do I lost anything?

0 Pavel Botev over 8 years ago in reply to Phil Chang

TI__Guru**** 170625 points

Hi Phil,

You need first enable McASP0 in device PRCM, see register CM_PER_MCASP0_CLKCTRL at address 0x44E00034.

Then McASP0 registers can be accessed at base address 0x48038000

Regards,
Pavel

0 Phil Chang over 8 years ago in reply to Pavel Botev

Intellectual 580 points

Got it! many thanks!

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Linux/AM3352: Use pin mcasp0_aclkx to generate clock