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Message-Id: <20130719052601.314654160@linuxfoundation.org>
Date: Thu, 18 Jul 2013 22:25:38 -0700
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Helge Deller <deller@....de>
Subject: [ 21/72] parisc: document the shadow registers
3.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Helge Deller <deller@....de>
commit a83f58bcb24003b9de2364de7c829a263423ead7 upstream.
Signed-off-by: Helge Deller <deller@....de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
Documentation/parisc/registers | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/Documentation/parisc/registers
+++ b/Documentation/parisc/registers
@@ -78,6 +78,14 @@ Shadow Registers used by interruption h
TOC enable bit 1
=========================================================================
+
+The PA-RISC architecture defines 7 registers as "shadow registers".
+Those are used in RETURN FROM INTERRUPTION AND RESTORE instruction to reduce
+the state save and restore time by eliminating the need for general register
+(GR) saves and restores in interruption handlers.
+Shadow registers are the GRs 1, 8, 9, 16, 17, 24, and 25.
+
+=========================================================================
Register usage notes, originally from John Marvin, with some additional
notes from Randolph Chung.
--
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