path: root/docs
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authorJeenu Viswambharan <jeenu.viswambharan@arm.com>2014-05-12 15:28:47 +0100
committerJeenu Viswambharan <jeenu.viswambharan@arm.com>2014-05-16 17:11:31 +0100
commit2da8d8bfc0877b9c723514133554dfee4c0638f1 (patch)
tree5178aafe28b80e33b6581663bee66b9d2194688a /docs
parentc3c1e9b0abe1a879dad4400421ad00849231eb3c (diff)
Add build configuration for timer save/restore
At present, non-secure timer register contents are saved and restored as part of world switch by BL3-1. This effectively means that the non-secure timer stops, and non-secure timer interrupts are prevented from asserting until BL3-1 switches back, introducing latency for non-secure services. Often, secure world might depend on alternate sources for secure interrupts (secure timer or platform timer) instead of non-secure timers, in which case this save and restore is unnecessary. This patch introduces a boolean build-time configuration NS_TIMER_SWITCH to choose whether or not to save and restore non-secure timer registers upon world switch. The default choice is made not to save and restore them. Fixes ARM-software/tf-issues#148 Change-Id: I1b9d623606acb9797c3e0b02fb5ec7c0a414f37e
Diffstat (limited to 'docs')
1 files changed, 5 insertions, 0 deletions
diff --git a/docs/user-guide.md b/docs/user-guide.md
index edf03f0..e7f0df5 100644
--- a/docs/user-guide.md
+++ b/docs/user-guide.md
@@ -141,6 +141,11 @@ performed.
* `DEBUG`: Chooses between a debug and release build. It can take either 0
(release) or 1 (debug) as values. 0 is the default
+* `NS_TIMER_SWITCH`: Enable save and restore for non-secure timer register
+ contents upon world switch. It can take either 0 (don't save and restore) or
+ 1 (do save and restore). 0 is the default. An SPD could set this to 1 if it
+ wants the timer registers to be saved and restored
* `PLAT`: Choose a platform to build ARM Trusted Firmware for. The chosen
platform name must be the name of one of the directories under the `plat/`
directory other than `common`