Pull the special handling of extra voices out of
snd_emu10k1_pcm_init_voice(), simplify snd_emu10k1_playback_pointer(),
and make the logic overall clearer. Also, add verbose comments.
Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@xxxxxx>
---
sound/pci/emu10k1/emupcm.c | 81 ++++++++++++++++++++++++--------------
1 file changed, 52 insertions(+), 29 deletions(-)
diff --git a/sound/pci/emu10k1/emupcm.c b/sound/pci/emu10k1/emupcm.c
index 063918397a5f..89f7e85034b6 100644
--- a/sound/pci/emu10k1/emupcm.c
+++ b/sound/pci/emu10k1/emupcm.c
@@ -269,9 +269,6 @@ static void snd_emu10k1_pcm_init_voice(struct snd_emu10k1 *emu,
memcpy(send_amount, &mix->send_volume[tmp][0], 8);
}
- if (master) {
- evoice->epcm->ccca_start_addr = start_addr + 64 - 3;
- }
if (stereo) {
// Not really necessary for the slave, but it doesn't hurt
snd_emu10k1_ptr_write(emu, CPF, voice, CPF_STEREO_MASK);
@@ -299,12 +296,7 @@ static void snd_emu10k1_pcm_init_voice(struct snd_emu10k1 *emu,
pitch_target = PITCH_48000; /* Disable interpolators on emu1010 card */
else
pitch_target = emu10k1_calc_pitch_target(runtime->rate);
- if (extra)
- snd_emu10k1_ptr_write(emu, CCCA, voice, (end_addr - 3) |
- emu10k1_select_interprom(pitch_target) |
- (w_16 ? 0 : CCCA_8BITSELECT));
- else
- snd_emu10k1_ptr_write(emu, CCCA, voice, (start_addr + 64 - 3) |
+ snd_emu10k1_ptr_write(emu, CCCA, voice,
emu10k1_select_interprom(pitch_target) |
(w_16 ? 0 : CCCA_8BITSELECT));
/* Clear filter delay memory */
@@ -401,6 +393,7 @@ static int snd_emu10k1_playback_prepare(struct snd_pcm_substream *substream)
snd_emu10k1_pcm_init_voice(emu, 1, 1, epcm->extra, w_16, false,
start_addr, end_addr, NULL);
start_addr >>= stereo;
+ epcm->ccca_start_addr = start_addr;
end_addr = start_addr + runtime->buffer_size;
snd_emu10k1_pcm_init_voice(emu, 1, 0, epcm->voices[0], w_16, stereo,
start_addr, end_addr,
@@ -428,13 +421,8 @@ static int snd_emu10k1_efx_playback_prepare(struct snd_pcm_substream *substream)
snd_emu10k1_pcm_init_voice(emu, 1, 1, epcm->extra, true, false,
start_addr, start_addr + (channel_size / 2), NULL);
- /* only difference with the master voice is we use it for the pointer */
- snd_emu10k1_pcm_init_voice(emu, 1, 0, epcm->voices[0], true, false,
- start_addr, start_addr + channel_size,
- &emu->efx_pcm_mixer[0]);
-
- start_addr += channel_size;
- for (i = 1; i < NUM_EFX_PLAYBACK; i++) {
+ epcm->ccca_start_addr = start_addr;
+ for (i = 0; i < NUM_EFX_PLAYBACK; i++) {
snd_emu10k1_pcm_init_voice(emu, 0, 0, epcm->voices[i], true, false,
start_addr, start_addr + channel_size,
&emu->efx_pcm_mixer[i]);
@@ -540,13 +528,45 @@ static void snd_emu10k1_playback_prepare_voices(struct snd_emu10k1 *emu,
bool w_16, bool stereo,
int channels)
{
+ struct snd_pcm_substream *substream = epcm->substream;
+ struct snd_pcm_runtime *runtime = substream->runtime;
+ unsigned eloop_start = epcm->start_addr >> w_16;
+ unsigned loop_start = eloop_start >> stereo;
+ unsigned eloop_size = runtime->period_size;
+ unsigned loop_size = runtime->buffer_size;
u32 sample = w_16 ? 0 : 0x80808080;
+ // To make the playback actually start at the 1st frame,
+ // we need to compensate for two circumstances:
+ // - The actual position is delayed by the cache size (64 frames)
+ // - The interpolator is centered around the 4th frame
+ loop_start += 64 - 3;
for (int i = 0; i < channels; i++) {
unsigned voice = epcm->voices[i]->number;
+ snd_emu10k1_ptr_write(emu, CCCA_CURRADDR, voice, loop_start);
+ loop_start += loop_size;
snd_emu10k1_playback_fill_cache(emu, voice, sample, stereo);
}
+ // The interrupt is triggered when CCCA_CURRADDR (CA) wraps around,
+ // which is ahead of the actual playback position, so the interrupt
+ // source needs to be delayed.
+ //
+ // In principle, this wouldn't need to be the cache's entire size - in
+ // practice, CCR_CACHEINVALIDSIZE (CIS) > `fetch threshold` has never
+ // been observed, and assuming 40 _bytes_ should be safe.
+ //
+ // The cache fills are somewhat random, which makes it impossible to
+ // align them with the interrupts. This makes a non-delayed interrupt
+ // source not practical, as the interrupt handler would have to wait
+ // for (CA - CIS) >= period_boundary for every channel in the stream.
+ //
+ // This is why all other (open) drivers for these chips use timer-based
+ // interrupts.
+ //
+ eloop_start += eloop_size - 3;
+ snd_emu10k1_ptr_write(emu, CCCA_CURRADDR, epcm->extra->number, eloop_start);
+
// It takes a moment until the cache fills complete,
// but the unmuting takes long enough for that.
}
@@ -746,24 +766,27 @@ static snd_pcm_uframes_t snd_emu10k1_playback_pointer(struct snd_pcm_substream *
struct snd_emu10k1 *emu = snd_pcm_substream_chip(substream);
struct snd_pcm_runtime *runtime = substream->runtime;
struct snd_emu10k1_pcm *epcm = runtime->private_data;
- unsigned int ptr;
+ int ptr;
if (!epcm->running)
return 0;
+
ptr = snd_emu10k1_ptr_read(emu, CCCA, epcm->voices[0]->number) & 0x00ffffff;
-#if 0 /* Perex's code */
- ptr += runtime->buffer_size;
ptr -= epcm->ccca_start_addr;
- ptr %= runtime->buffer_size;
-#else /* EMU10K1 Open Source code from Creative */
- if (ptr < epcm->ccca_start_addr)
- ptr += runtime->buffer_size - epcm->ccca_start_addr;
- else {
- ptr -= epcm->ccca_start_addr;
- if (ptr >= runtime->buffer_size)
- ptr -= runtime->buffer_size;
- }
-#endif
+
+ // This is the size of the whole cache minus the interpolator read-ahead,
+ // which leads us to the actual playback position.
+ //
+ // The cache is constantly kept mostly filled, so in principle we could
+ // return a more advanced position representing how far the hardware has
+ // already read the buffer, and set runtime->delay accordingly. However,
+ // this would be slightly different for every channel (and remarkably slow
+ // to obtain), so only a fixed worst-case value would be practical.
+ //
+ ptr -= 64 - 3;
+ if (ptr < 0)
+ ptr += runtime->buffer_size;
+
/*
dev_dbg(emu->card->dev,
"ptr = 0x%lx, buffer_size = 0x%lx, period_size = 0x%lx\n",
--
2.40.0.152.g15d061e6df
