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gba: allocate the frame buffers before the ROM cache; skip only when behind #11

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Merged
finger563 merged 1 commit into from
Oct 24, 2026
Merged

gba: allocate the frame buffers before the ROM cache; skip only when behind #11

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24 changes: 22 additions & 2 deletions components/gba/src/gba.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
#include <thread>
#include <vector>

#include <esp_heap_caps.h>
#include <esp_timer.h>

#include "box-emu.hpp"
Expand Down Expand Up @@ -183,8 +184,12 @@ size_t gpsp_obj_priority_bytes(void);
// HAL's ROM arena first, then the heap. The arena stays reserved at its boot
// address for the carts that keep address-bound save states in it (MGS,
// TPM); releasing it for the cache let it come back somewhere else.
// The core asks for blocks until it has ROM_BUFFER_SIZE or one fails, so the
// heap ones stop short of the last PSRAM_RESERVE bytes: the frame buffers,
// the pause menu's screenshots and a save state's buffer come after it.
namespace {
uint32_t g_arena_slices = 0; // bit i: slice i of the ROM arena is a cache block
constexpr size_t PSRAM_RESERVE = 2 * 1024 * 1024;
}
extern "C" void *gpsp_rom_block_alloc(size_t bytes) {
auto &emu = Tab5Emu::get();
Expand All @@ -197,6 +202,9 @@ extern "C" void *gpsp_rom_block_alloc(size_t bytes) {
}
}
}
if (heap_caps_get_free_size(MALLOC_CAP_SPIRAM) < bytes + PSRAM_RESERVE) {
return nullptr; // a smaller cache pages the rest of the ROM from the card
}
return malloc(bytes);
}
extern "C" void gpsp_rom_block_free(void *p) {
Expand Down Expand Up @@ -246,6 +254,15 @@ void init_gba(const std::string &rom_path) {
gba_shared_free();
return;
}
// the two frame buffers video_cb alternates between, before the ROM cache
// takes what PSRAM is left (allocated on first use, they came after it, and
// with the second one missing no frame reached the screen)
auto &emu = BoxEmu::get();
if (!emu.frame_buffer0() || !emu.frame_buffer1()) {
fmt::print("gba: no memory for the frame buffers\n");
gba_shared_free();
return;
}
retro_set_environment(&environ_cb);
retro_set_video_refresh(&video_cb);
retro_set_audio_sample_batch(&audio_batch_cb);
Expand All @@ -263,7 +280,6 @@ void init_gba(const std::string &rom_path) {
struct retro_system_av_info av = {};
retro_get_system_av_info(&av);
g_fps = av.timing.fps;
auto &emu = BoxEmu::get();
emu.palette(nullptr);
g_audio_rate = static_cast<uint32_t>(av.timing.sample_rate);
emu.audio_sample_rate(g_audio_rate);
Expand Down Expand Up @@ -299,7 +315,11 @@ void run_gba_rom() {
if (g_next_due == 0 || start > g_next_due + 2 * frame_us) {
g_next_due = start;
}
const bool behind = start > g_next_due;
// the sleep below wakes up to a tick (1 ms) after the deadline, so a frame
// that starts just past it is on time; only a quarter frame late is behind
// (with no slack every frame after a sleep was "behind" and every other
// frame was skipped, even at 4 ms a frame)
const bool behind = start > g_next_due + frame_us / 4;
// the core's "auto" frameskip skips a frame when the host reports an
// audio underrun (up to 30 in a row). Rendering is a small part of a
// frame here, so skipping barely catches up but makes the output choppy:
Expand Down
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