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authorRobin Getz <rgetz@blackfin.uclinux.org>2008-08-14 15:12:55 +0800
committerBryan Wu <cooloney@kernel.org>2008-08-14 15:12:55 +0800
commit251383c7c50cf17664a4d7d60d3a52d8827a0e11 (patch)
treef4b8368ddfe748040b80762bfd01d08b7e635bc4 /arch/blackfin/Kconfig
parentcd8fb8df1458df7f3b99fd112e722b05f42c64d9 (diff)
downloadop-kernel-dev-251383c7c50cf17664a4d7d60d3a52d8827a0e11.zip
op-kernel-dev-251383c7c50cf17664a4d7d60d3a52d8827a0e11.tar.gz
Blackfin arch: Allow ins functions to have a low latency version
Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org> Signed-off-by: Bryan Wu <cooloney@kernel.org>
Diffstat (limited to 'arch/blackfin/Kconfig')
-rw-r--r--arch/blackfin/Kconfig27
1 files changed, 27 insertions, 0 deletions
diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index cc2add7..ededf93 100644
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -622,6 +622,33 @@ config CPLB_SWITCH_TAB_L1
If enabled, the CPLB Switch Tables are linked
into L1 data memory. (less latency)
+comment "Speed Optimizations"
+config BFIN_INS_LOWOVERHEAD
+ bool "ins[bwl] low overhead, higher interrupt latency"
+ default y
+ help
+ Reads on the Blackfin are speculative. In Blackfin terms, this means
+ they can be interrupted at any time (even after they have been issued
+ on to the external bus), and re-issued after the interrupt occurs.
+ For memory - this is not a big deal, since memory does not change if
+ it sees a read.
+
+ If a FIFO is sitting on the end of the read, it will see two reads,
+ when the core only sees one since the FIFO receives both the read
+ which is cancelled (and not delivered to the core) and the one which
+ is re-issued (which is delivered to the core).
+
+ To solve this, interrupts are turned off before reads occur to
+ I/O space. This option controls which the overhead/latency of
+ controlling interrupts during this time
+ "n" turns interrupts off every read
+ (higher overhead, but lower interrupt latency)
+ "y" turns interrupts off every loop
+ (low overhead, but longer interrupt latency)
+
+ default behavior is to leave this set to on (type "Y"). If you are experiencing
+ interrupt latency issues, it is safe and OK to turn this off.
+
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