mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-28 20:02:17 +00:00
![Russell King](/assets/img/avatar_default.png)
This just leaves include/asm-arm/plat-* to deal with. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
167 lines
6.6 KiB
Text
167 lines
6.6 KiB
Text
2.5.2-rmk5
|
|
----------
|
|
|
|
This is the first kernel that contains a major shake up of some of the
|
|
major architecture-specific subsystems.
|
|
|
|
Firstly, it contains some pretty major changes to the way we handle the
|
|
MMU TLB. Each MMU TLB variant is now handled completely separately -
|
|
we have TLB v3, TLB v4 (without write buffer), TLB v4 (with write buffer),
|
|
and finally TLB v4 (with write buffer, with I TLB invalidate entry).
|
|
There is more assembly code inside each of these functions, mainly to
|
|
allow more flexible TLB handling for the future.
|
|
|
|
Secondly, the IRQ subsystem.
|
|
|
|
The 2.5 kernels will be having major changes to the way IRQs are handled.
|
|
Unfortunately, this means that machine types that touch the irq_desc[]
|
|
array (basically all machine types) will break, and this means every
|
|
machine type that we currently have.
|
|
|
|
Lets take an example. On the Assabet with Neponset, we have:
|
|
|
|
GPIO25 IRR:2
|
|
SA1100 ------------> Neponset -----------> SA1111
|
|
IIR:1
|
|
-----------> USAR
|
|
IIR:0
|
|
-----------> SMC9196
|
|
|
|
The way stuff currently works, all SA1111 interrupts are mutually
|
|
exclusive of each other - if you're processing one interrupt from the
|
|
SA1111 and another comes in, you have to wait for that interrupt to
|
|
finish processing before you can service the new interrupt. Eg, an
|
|
IDE PIO-based interrupt on the SA1111 excludes all other SA1111 and
|
|
SMC9196 interrupts until it has finished transferring its multi-sector
|
|
data, which can be a long time. Note also that since we loop in the
|
|
SA1111 IRQ handler, SA1111 IRQs can hold off SMC9196 IRQs indefinitely.
|
|
|
|
|
|
The new approach brings several new ideas...
|
|
|
|
We introduce the concept of a "parent" and a "child". For example,
|
|
to the Neponset handler, the "parent" is GPIO25, and the "children"d
|
|
are SA1111, SMC9196 and USAR.
|
|
|
|
We also bring the idea of an IRQ "chip" (mainly to reduce the size of
|
|
the irqdesc array). This doesn't have to be a real "IC"; indeed the
|
|
SA11x0 IRQs are handled by two separate "chip" structures, one for
|
|
GPIO0-10, and another for all the rest. It is just a container for
|
|
the various operations (maybe this'll change to a better name).
|
|
This structure has the following operations:
|
|
|
|
struct irqchip {
|
|
/*
|
|
* Acknowledge the IRQ.
|
|
* If this is a level-based IRQ, then it is expected to mask the IRQ
|
|
* as well.
|
|
*/
|
|
void (*ack)(unsigned int irq);
|
|
/*
|
|
* Mask the IRQ in hardware.
|
|
*/
|
|
void (*mask)(unsigned int irq);
|
|
/*
|
|
* Unmask the IRQ in hardware.
|
|
*/
|
|
void (*unmask)(unsigned int irq);
|
|
/*
|
|
* Re-run the IRQ
|
|
*/
|
|
void (*rerun)(unsigned int irq);
|
|
/*
|
|
* Set the type of the IRQ.
|
|
*/
|
|
int (*type)(unsigned int irq, unsigned int, type);
|
|
};
|
|
|
|
ack - required. May be the same function as mask for IRQs
|
|
handled by do_level_IRQ.
|
|
mask - required.
|
|
unmask - required.
|
|
rerun - optional. Not required if you're using do_level_IRQ for all
|
|
IRQs that use this 'irqchip'. Generally expected to re-trigger
|
|
the hardware IRQ if possible. If not, may call the handler
|
|
directly.
|
|
type - optional. If you don't support changing the type of an IRQ,
|
|
it should be null so people can detect if they are unable to
|
|
set the IRQ type.
|
|
|
|
For each IRQ, we keep the following information:
|
|
|
|
- "disable" depth (number of disable_irq()s without enable_irq()s)
|
|
- flags indicating what we can do with this IRQ (valid, probe,
|
|
noautounmask) as before
|
|
- status of the IRQ (probing, enable, etc)
|
|
- chip
|
|
- per-IRQ handler
|
|
- irqaction structure list
|
|
|
|
The handler can be one of the 3 standard handlers - "level", "edge" and
|
|
"simple", or your own specific handler if you need to do something special.
|
|
|
|
The "level" handler is what we currently have - its pretty simple.
|
|
"edge" knows about the brokenness of such IRQ implementations - that you
|
|
need to leave the hardware IRQ enabled while processing it, and queueing
|
|
further IRQ events should the IRQ happen again while processing. The
|
|
"simple" handler is very basic, and does not perform any hardware
|
|
manipulation, nor state tracking. This is useful for things like the
|
|
SMC9196 and USAR above.
|
|
|
|
So, what's changed?
|
|
|
|
1. Machine implementations must not write to the irqdesc array.
|
|
|
|
2. New functions to manipulate the irqdesc array. The first 4 are expected
|
|
to be useful only to machine specific code. The last is recommended to
|
|
only be used by machine specific code, but may be used in drivers if
|
|
absolutely necessary.
|
|
|
|
set_irq_chip(irq,chip)
|
|
|
|
Set the mask/unmask methods for handling this IRQ
|
|
|
|
set_irq_handler(irq,handler)
|
|
|
|
Set the handler for this IRQ (level, edge, simple)
|
|
|
|
set_irq_chained_handler(irq,handler)
|
|
|
|
Set a "chained" handler for this IRQ - automatically
|
|
enables this IRQ (eg, Neponset and SA1111 handlers).
|
|
|
|
set_irq_flags(irq,flags)
|
|
|
|
Set the valid/probe/noautoenable flags.
|
|
|
|
set_irq_type(irq,type)
|
|
|
|
Set active the IRQ edge(s)/level. This replaces the
|
|
SA1111 INTPOL manipulation, and the set_GPIO_IRQ_edge()
|
|
function. Type should be one of IRQ_TYPE_xxx defined in
|
|
<linux/irq.h>
|
|
|
|
3. set_GPIO_IRQ_edge() is obsolete, and should be replaced by set_irq_type.
|
|
|
|
4. Direct access to SA1111 INTPOL is deprecated. Use set_irq_type instead.
|
|
|
|
5. A handler is expected to perform any necessary acknowledgement of the
|
|
parent IRQ via the correct chip specific function. For instance, if
|
|
the SA1111 is directly connected to a SA1110 GPIO, then you should
|
|
acknowledge the SA1110 IRQ each time you re-read the SA1111 IRQ status.
|
|
|
|
6. For any child which doesn't have its own IRQ enable/disable controls
|
|
(eg, SMC9196), the handler must mask or acknowledge the parent IRQ
|
|
while the child handler is called, and the child handler should be the
|
|
"simple" handler (not "edge" nor "level"). After the handler completes,
|
|
the parent IRQ should be unmasked, and the status of all children must
|
|
be re-checked for pending events. (see the Neponset IRQ handler for
|
|
details).
|
|
|
|
7. fixup_irq() is gone, as is arch/arm/mach-*/include/mach/irq.h
|
|
|
|
Please note that this will not solve all problems - some of them are
|
|
hardware based. Mixing level-based and edge-based IRQs on the same
|
|
parent signal (eg neponset) is one such area where a software based
|
|
solution can't provide the full answer to low IRQ latency.
|
|
|