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ARM: 6940/1: fiq: Briefly document driver responsibilities for suspend/resume

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Drivers which make use of the FIQ interrupt may require the state
of the FIQ mode registers to be preserved across suspend/resume.

Because the FIQ mode registers are not saved and restored
automatically by the kernel, driver authors will need to do the
appropriate save/restore in their own driver suspend/resume
handlers.

Implementing global automatic save/restore of the FIQ state does
not appear appropriate, since this by itself is not sufficient for
FIQ-based drivers to function correctly across suspend/resume in
any case.

This patch adds a brief explanatory note to fiq.h documenting the
requirement placed on driver authors.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Dave Martin
2011-05-24 12:11:48 +01:00
committed by Russell King
parent dc2eb928a1
commit 2846d84ffa
1 changed files with 7 additions and 0 deletions
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7
arch/arm/include/asm/fiq.h
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@@ -4,6 +4,13 @@
* Support for FIQ on ARM architectures. * Support for FIQ on ARM architectures.
* Written by Philip Blundell <philb@gnu.org>, 1998 * Written by Philip Blundell <philb@gnu.org>, 1998
* Re-written by Russell King * Re-written by Russell King
*
* NOTE: The FIQ mode registers are not magically preserved across
* suspend/resume.
*
* Drivers which require these registers to be preserved across power
* management operations must implement appropriate suspend/resume handlers to
* save and restore them.
*/ */
#ifndef __ASM_FIQ_H #ifndef __ASM_FIQ_H