iPod Classic: disable IRAM1

On Classic, IRAM1 (second 128Kb of a total of 256KB available IRAM) is
slower than DRAM. Codecs that actually are using regions of IRAM1 runs
faster when DRAM is used, so IRAM1 is disabled and only IRAM0 remains
enabled: 48KB for core and 80KB for codecs/plugins.

The next test_codec results shows how decode time is decreased:

file           boosted     unboosted
*.ra           ~1.5%       ~0.5%
*.mpc          ~21%        ~4.5%
*.ogg          ~0.5%       ~0%
nero_he*.m4a   ~8%         ~1%
nero*.m4a      ~25%        ~7%
wmapro*.wma    ~4.5%       ~0%
wma*.wma       ~25%        ~7%

In addition there is a small power save when IRAM1 HW is disabled.

Change-Id: I102adee11458e82037f23076d5d5956e23235de8

1 files changed, 3 insertions, 0 deletions

diff --git a/firmware/target/arm/s5l8702/system-s5l8702.c b/firmware/target/arm/s5l8702/system-s5l8702.c
index 459f4c36c6..9257aff85a 100644
--- a/firmware/target/arm/s5l8702/system-s5l8702.c
+++ b/firmware/target/arm/s5l8702/system-s5l8702.c
@@ -199,6 +199,9 @@ enum {
 
 void system_init(void)
 {
+    /* disable IRAM1 (not used because it is slower than DRAM) */
+    clockgate_enable(CLOCKGATE_SM1, false);
+
     clocking_init(clk_modes, 0);
 #ifndef BOOTLOADER
     gpio_preinit();