From fa75064d92fdec157d75375bca06c77fb30c25df Mon Sep 17 00:00:00 2001 From: Oswald Buddenhagen Date: Wed, 17 May 2023 19:42:56 +0200 Subject: [PATCH] ALSA: emu10k1: refactor PCM playback address handling 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 Link: https://lore.kernel.org/r/20230517174256.3657060-9-oswald.buddenhagen@gmx.de Signed-off-by: Takashi Iwai --- 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",