1. 21 May, 2008 1 commit
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    • David Howells's avatar
      IRQ: Maintain regs pointer globally rather than passing to IRQ handlers · 7d12e780
      David Howells authored
      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
      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:
      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
      Signed-Off-By: default avatarDavid Howells <dhowells@redhat.com>
      (cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
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    • Russell King's avatar
      [PATCH] IRQ type flags · 9ded96f2
      Russell King authored
      Some ARM platforms have the ability to program the interrupt controller to
      detect various interrupt edges and/or levels.  For some platforms, this is
      critical to setup correctly, particularly those which the setting is dependent
      on the device.
      Currently, ARM drivers do (eg) the following:
      	err = request_irq(irq, ...);
      	set_irq_type(irq, IRQT_RISING);
      However, if the interrupt has previously been programmed to be level sensitive
      (for whatever reason) then this will cause an interrupt storm.
      Hence, if we combine set_irq_type() with request_irq(), we can then safely set
      the type prior to unmasking the interrupt.  The unfortunate problem is that in
      order to support this, these flags need to be visible outside of the ARM
      architecture - drivers such as smc91x need these flags and they're
      Finally, the SA_TRIGGER_* flag passed to request_irq() should reflect the
      property that the device would like.  The IRQ controller code should do its
      best to select the most appropriate supported mode.
      Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
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