diff options
Diffstat (limited to 'firmware/target/mips/ingenic_x1000/kernel-x1000.c')
-rw-r--r-- | firmware/target/mips/ingenic_x1000/kernel-x1000.c | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/firmware/target/mips/ingenic_x1000/kernel-x1000.c b/firmware/target/mips/ingenic_x1000/kernel-x1000.c new file mode 100644 index 0000000000..c8105a3446 --- /dev/null +++ b/firmware/target/mips/ingenic_x1000/kernel-x1000.c | |||
@@ -0,0 +1,74 @@ | |||
1 | /*************************************************************************** | ||
2 | * __________ __ ___. | ||
3 | * Open \______ \ ____ ____ | | _\_ |__ _______ ___ | ||
4 | * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / | ||
5 | * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < | ||
6 | * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ | ||
7 | * \/ \/ \/ \/ \/ | ||
8 | * $Id$ | ||
9 | * | ||
10 | * Copyright (C) 2021 Aidan MacDonald | ||
11 | * | ||
12 | * This program is free software; you can redistribute it and/or | ||
13 | * modify it under the terms of the GNU General Public License | ||
14 | * as published by the Free Software Foundation; either version 2 | ||
15 | * of the License, or (at your option) any later version. | ||
16 | * | ||
17 | * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY | ||
18 | * KIND, either express or implied. | ||
19 | * | ||
20 | ****************************************************************************/ | ||
21 | |||
22 | #include "kernel.h" | ||
23 | #include "system.h" | ||
24 | #include "x1000/ost.h" | ||
25 | |||
26 | /* TODO: implement a CPU frequency switching policy based on CPU utilization | ||
27 | * | ||
28 | * The basic assumption is that the workload consumes a fixed number of CPU | ||
29 | * cycles per second on average (= utilization), so we can set the frequency | ||
30 | * based on that value. Audio playback should fit this usage pattern well, so | ||
31 | * it's a good fit for Rockbox. | ||
32 | * | ||
33 | * It's easier to understand in terms of fluid flow -- we need to keep | ||
34 | * a reservoir of water topped up, CPU frequency is the inflow rate, and | ||
35 | * CPU utilization is the outflow rate. The goal is to avoid running dry | ||
36 | * and minimize the inflow rate. | ||
37 | * | ||
38 | * The only tricky part here is handing usage spikes -- CPU frequency has to | ||
39 | * increase faster than utilization or there's a risk of audio dropouts. | ||
40 | * | ||
41 | * Rockbox CPU boost could be used as a hint to scale up frequency faster. | ||
42 | * If that's not necessary to get good results, HAVE_ADJUSTABLE_CPU_FREQ can | ||
43 | * be disabled entirely. | ||
44 | */ | ||
45 | |||
46 | #define CPU_IDLE_SAMPLES 100 | ||
47 | |||
48 | void tick_start(unsigned interval_in_ms) | ||
49 | { | ||
50 | jz_writef(OST_CTRL, PRESCALE1_V(BY_16)); | ||
51 | jz_write(OST_1DFR, interval_in_ms*(X1000_EXCLK_FREQ/16000)); | ||
52 | jz_write(OST_1CNT, 0); | ||
53 | jz_write(OST_1FLG, 0); | ||
54 | jz_write(OST_1MSK, 0); | ||
55 | jz_setf(OST_ENABLE, OST1); | ||
56 | } | ||
57 | |||
58 | void OST(void) | ||
59 | { | ||
60 | /* CPU idle time accounting */ | ||
61 | uint32_t now = __ost_read32(); | ||
62 | uint32_t div = now - __cpu_idle_reftick; | ||
63 | if(div != 0) { | ||
64 | uint32_t fraction = 1000 * __cpu_idle_ticks / div; | ||
65 | __cpu_idle_avg += fraction - __cpu_idle_avg / CPU_IDLE_SAMPLES; | ||
66 | __cpu_idle_cur = __cpu_idle_avg / CPU_IDLE_SAMPLES; | ||
67 | __cpu_idle_ticks = 0; | ||
68 | __cpu_idle_reftick = now; | ||
69 | } | ||
70 | |||
71 | /* Call regular kernel tick */ | ||
72 | jz_write(OST_1FLG, 0); | ||
73 | call_tick_tasks(); | ||
74 | } | ||