Okay... I think I've got a problem that isn't covered by the usual examples. I'm now trying to implment a second-level interrupt demuxer. My exception handler, when it sees a certain bit set in the CP0_CAUSE register set, attempts to read from the second-level controller. The problem is, that code looks like this: li t0, 0xfc000000 lb t1, 0xc(t0) Which, as you can see, attempts to access address 0xfc00000c. And then I get: Unable to handle kernel paging request at virtual address fc00000c, epc == 801af2ac, ra == 80102eb8 Oops in fault.c::do_page_fault, line 206: I'm guessing I'm in trouble here. My instincts tell me the the only way out of this might be to add a wired TLB entry to make certain I can always access physical address 0xfc00000c... but I'm hoping there is a better solution than tying up a TLB entry like that. After all, isn't that what ioremap is supposed to do? Matt -- Matthew D. Dharm Senior Software Designer Momentum Computer Inc. 1815 Aston Ave. Suite 107 (760) 431-8663 X-115 Carlsbad, CA 92008-7310 Momentum Works For You www.momenco.com > -----Original Message----- > From: linux-mips-bounce@linux-mips.org > [mailto:linux-mips-bounce@linux-mips.org]On Behalf Of Jun Sun > Sent: Thursday, August 29, 2002 1:46 PM > To: Matthew Dharm > Cc: Linux-MIPS > Subject: Re: Interrupt handling.... > > > Matthew Dharm wrote: > > I've taken it upon myself to re-write some interrupt > handling code. > > It's a mess, and it needs cleaning. > > > > That is usually a right attitude to start ... :=) > > > > > An interrupt handler must be registered with > set_except_vector(0, ...) > > which must return a numeric code in the range of > 0..NR_IRQS -- it can > > do this in any way it wants, including limited function calls (ie > > there is a stack in place). > > > > Interrupt is setup throught request_irq()/setup_irq(). > set_except_vector() > for setting exception handlers, which is different from interrupts. > > > The irq_desc array of irq_desc_t structures is where the magic > > happens. The value returned by the interrupt handler is > used as an > > index into this array to do the dispatch a specific handler. The > > 'status' and 'action' fields are pretty much > self-explanatory. The > > 'handler' field seems to point to a set of function > pointers used for > > enabling/disabling the IRQ. But what is 'depth' for? > Boards seem to > > set it to either 0 or 1 commonly, but I don't see why. > > For nested disabling and enabling of interrupts. > > > I also don't > > see how IRQ sharing is accomplished... > > Yes, it is there. See do_IRQ() and a sub-routine > handle_event() (or something > like that) > > > Is this pretty much how it all works? > > I have a more detailed description in my porting guide. > > http://linux.junsun.net/porting-howto/porting-howto.html#cha pter-interrupt Jun
