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ar71xx: fix lzma loader performance issues

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Some bootloaders set a cache cohenrency to a very slow mode. Use code from
Linux kernel to set it to "Cacheable, noncoherent, write-back, write
allocate".

Perfomance impact is significant on TP-Link EAP245 board, kernel
decompression time fall from 33 seconds to less than 1.

Signed-off-by: Julien Dusser <julien.dusser@free.fr>
This commit is contained in:
Julien Dusser 2017-07-19 14:52:35 +02:00 committed by Felix Fietkau
parent 06e41056aa
commit 8c5702f2a0
1 changed files with 13 additions and 0 deletions
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13
target/linux/ar71xx/image/lzma-loader/src/head.S
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@ -42,6 +42,19 @@ LEAF(startup)
mtc0 t0, CP0_STATUS
ehb
/*
* Some bootloaders set the 'Kseg0 coherency algorithm' to
* 'Cacheable, noncoherent, write-through, no write allocate'
* and this cause performance issues. Let's go and change it to
* 'Cacheable, noncoherent, write-back, write allocate'
*/
mfc0 t0, CP0_CONFIG
li t1, ~7 #~CONF_CM_CMASK
and t0, t1
ori t0, 3 #CONF_CM_CACHABLE_NONCOHERENT
mtc0 t0, CP0_CONFIG
nop
mtc0 zero, CP0_COUNT
mtc0 zero, CP0_COMPARE
ehb