Maintain a per-CPU global "struct pt_regs *" variable which can be used instead
of passing regs around manually through all ~1800 interrupt handlers in the
Linux kernel.
The regs pointer is used in few places, but it potentially costs both stack
space and code to pass it around. On the FRV arch, removing the regs parameter
from all the genirq function results in a 20% speed up of the IRQ exit path
(ie: from leaving timer_interrupt() to leaving do_IRQ()).
Where appropriate, an arch may override the generic storage facility and do
something different with the variable. On FRV, for instance, the address is
maintained in GR28 at all times inside the kernel as part of general exception
handling.
Having looked over the code, it appears that the parameter may be handed down
through up to twenty or so layers of functions. Consider a USB character
device attached to a USB hub, attached to a USB controller that posts its
interrupts through a cascaded auxiliary interrupt controller. A character
device driver may want to pass regs to the sysrq handler through the input
layer which adds another few layers of parameter passing.
I've build this code with allyesconfig for x86_64 and i386. I've runtested the
main part of the code on FRV and i386, though I can't test most of the drivers.
I've also done partial conversion for powerpc and MIPS - these at least compile
with minimal configurations.
This will affect all archs. Mostly the changes should be relatively easy.
Take do_IRQ(), store the regs pointer at the beginning, saving the old one:
struct pt_regs *old_regs = set_irq_regs(regs);
And put the old one back at the end:
set_irq_regs(old_regs);
Don't pass regs through to generic_handle_irq() or __do_IRQ().
In timer_interrupt(), this sort of change will be necessary:
- update_process_times(user_mode(regs));
- profile_tick(CPU_PROFILING, regs);
+ update_process_times(user_mode(get_irq_regs()));
+ profile_tick(CPU_PROFILING);
I'd like to move update_process_times()'s use of get_irq_regs() into itself,
except that i386, alone of the archs, uses something other than user_mode().
Some notes on the interrupt handling in the drivers:
(*) input_dev() is now gone entirely. The regs pointer is no longer stored in
the input_dev struct.
(*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking. It does
something different depending on whether it's been supplied with a regs
pointer or not.
(*) Various IRQ handler function pointers have been moved to type
irq_handler_t.
Signed-Off-By: David Howells <dhowells@redhat.com>
(cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
This "ftdi-elan" module is one half of the "driver" for
ELAN's Uxxx series adapters which are USB to PCMCIA CardBus
adapters. Currently only the U132 adapter is available and
it's module is called "u132-hcd".
When the USB hot plug subsystem detects a Uxxx series adapter
it should load this module.
Upon a successful device probe() the jtag device file interface
is created and the status workqueue started up.
The jtag device file interface exists for the purpose of
updating the firmware in the Uxxx series adapter, but as
yet it had never been used.
The status workqueue initializes the Uxxx and then sits there
polling the Uxxx until a supported PCMCIA CardBus device is
detected it will start the command and respond workqueues
and then load the module that handles the device. This will
initially be only the u132-hcd module. The status workqueue
then just polls the Uxxx looking for card ejects.
The command and respond workqueues implement a command
sequencer for communicating with the firmware on the other
side of the FTDI chip in the Uxxx. This "ftdi-elan" module
exports some functions to interface with the sequencer.
Note that this module is a USB client driver.
Note that the "u132-hcd" module is a (cut-down OHCI)
host controller.
Thus we have a topology with the parent of a host controller
being a USB client! This really stresses the USB subsystem
semaphore/mutex handling in the module removal.
Signed-off-by: Tony Olech <tony.olech@elandigitalsystems.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
David Howells