From: Helge Deller Date: Sat, 29 Jun 2013 11:24:16 +0000 (+0200) Subject: parisc: document the shadow registers X-Git-Tag: firefly_0821_release~6453^2~1569 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=fa8223db1d69e6de9c7c7210804e8bb284067954;p=firefly-linux-kernel-4.4.55.git parisc: document the shadow registers commit a83f58bcb24003b9de2364de7c829a263423ead7 upstream. Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman --- diff --git a/Documentation/parisc/registers b/Documentation/parisc/registers index dd3caddd1ad9..10c7d1730f5d 100644 --- a/Documentation/parisc/registers +++ b/Documentation/parisc/registers @@ -77,6 +77,14 @@ PSW default E value 0 Shadow Registers used by interruption handler code 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.