On Wed, Jun 4, 2008 at 9:46 AM, Marc Jones <[EMAIL PROTECTED]> wrote: > ron minnich wrote: >> This change adds some debug prints, and a comment warning to dts on cs5536. >> >> Most importantly it fixes a simple programming error which made it so most of >> the sets on the USB were not doing anything. The bug is also in V2. >> > > >> /* the /sizeof(u32) is to convert byte offsets into u32 offsets */ >> #define HCCPARAMS (0x08/sizeof(u32)) > > > > I don't understand this change. This is standard MMIO. The memory mapped > registers are defined 0h, 04h, 08h, 0Ah... > > You could > *(bar + 08h) |= 1 << 9; > or > *(bar + 09h) |= 1 << 1; >
This is an old C gotcha. Offsets are scaled by the pointer size. bar is a u32 *. So you see this: *(bar + HCCPARAMS) And it's easy to think that it is this: *(bar + 0xc) but actually, because bar is a u32 *, it will actually dereference this: *(bar + 0xc*4) i.e. the sizeof a u32 ... It has to work this way, because when you do bar++, it increments bar by 4, not 1. This is one of the reasons why, for mmio, we ought to be using structs. thanks ron -- coreboot mailing list [email protected] http://www.coreboot.org/mailman/listinfo/coreboot
