cannot comprehend this code!

ashlesha · 08-03-2006, 04:45 PM

I have a query about the following:

u32 pin_func;

pin_func = 0;
/* not valid for 1550 */
#ifdef CONFIG_AU1X00_USB_DEVICE
// 2nd USB port is USB device
pin_func = au_readl(SYS_PINFUNC) & (u32)(~0x8000);
au_writel(pin_func, SYS_PINFUNC);

Now SYS_PINFUNC is defined as 0xB190002C
the (u32)(~0x8000) means 0xB190002C & 0xFFFF1FFF right?

Then the original value of SYS_PINFUNC remains unchanged..so what is the
purpose of the above code?

Also how is u32 defined exactly?

Thanks
Ashlesha.

Tinkster · 08-03-2006, 06:46 PM

Impossible to tell from that snippet; I suggest you look through the include
files to find out ;}

Cheers,
Tink

ciotog · 08-04-2006, 01:32 AM

Quote:

Originally Posted by ashlesha

Now SYS_PINFUNC is defined as 0xB190002C
the (u32)(~0x8000) means 0xB190002C & 0xFFFF1FFF right?

No, ~0x80000 is 0xFFF7FFFF (subtract 0x8000 from 0xFFFFFFFF)

Quote:

Also how is u32 defined exactly?

It's an unsigned 32 bit value

EDIT: Also you're &ing the result of au_readl(SYS_PINFUNC) and (~0x8000), not the value SYS_PINFUNC and (~0x8000)

ashlesha · 08-04-2006, 11:50 AM

thanks! yeah..i realised that a little late..will fig out what the sys_pinfunc value is etc..

this is part of the Board support code for the AMD DB1500 board.

-Ashlesha.