[PATCH v2 2/2] ASoC: fsl_sai: Refine enable and disable sequence for synchronous mode
From: Shengjiu Wang
Date: Tue Aug 04 2020 - 22:28:44 EST
Tx synchronous with Rx:
The TCSR.TE is no need to enabled when only Rx is going to be enabled.
Check if need to disable RSCR.RE before disabling TCSR.TE.
Rx synchronous with Tx:
The RCSR.RE is no need to enabled when only Tx is going to be enabled.
Check if need to disable TSCR.RE before disabling RCSR.TE.
Signed-off-by: Shengjiu Wang <shengjiu.wang@xxxxxxx>
---
sound/soc/fsl/fsl_sai.c | 126 +++++++++++++++++++++++++++-------------
1 file changed, 85 insertions(+), 41 deletions(-)
diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index 84714fe7144c..f30c4e7b5221 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -517,6 +517,56 @@ static int fsl_sai_hw_free(struct snd_pcm_substream *substream,
return 0;
}
+/**
+ * fsl_sai_dir_is_synced - Check if stream is synced by the opposite stream
+ *
+ * SAI supports synchronous mode using bit/frame clocks of either Transmitter's
+ * or Receiver's for both streams. This function is used to check if clocks of
+ * the stream's are synced by the opposite stream.
+ *
+ * @sai: SAI context
+ * @dir: stream direction
+ */
+static inline bool fsl_sai_dir_is_synced(struct fsl_sai *sai, int dir)
+{
+ int adir = (dir == TX) ? RX : TX;
+
+ /* current dir in async mode while opposite dir in sync mode */
+ return !sai->synchronous[dir] && sai->synchronous[adir];
+}
+
+static void fsl_sai_config_disable(struct fsl_sai *sai, int dir)
+{
+ unsigned int ofs = sai->soc_data->reg_offset;
+ bool tx = dir == TX;
+ u32 xcsr, count = 100;
+
+ regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx, ofs),
+ FSL_SAI_CSR_TERE, 0);
+
+ /* TERE will remain set till the end of current frame */
+ do {
+ udelay(10);
+ regmap_read(sai->regmap, FSL_SAI_xCSR(tx, ofs), &xcsr);
+ } while (--count && xcsr & FSL_SAI_CSR_TERE);
+
+ regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx, ofs),
+ FSL_SAI_CSR_FR, FSL_SAI_CSR_FR);
+
+ /*
+ * For sai master mode, after several open/close sai,
+ * there will be no frame clock, and can't recover
+ * anymore. Add software reset to fix this issue.
+ * This is a hardware bug, and will be fix in the
+ * next sai version.
+ */
+ if (!sai->is_slave_mode) {
+ /* Software Reset */
+ regmap_write(sai->regmap, FSL_SAI_xCSR(tx, ofs), FSL_SAI_CSR_SR);
+ /* Clear SR bit to finish the reset */
+ regmap_write(sai->regmap, FSL_SAI_xCSR(tx, ofs), 0);
+ }
+}
static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
struct snd_soc_dai *cpu_dai)
@@ -525,7 +575,9 @@ static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
unsigned int ofs = sai->soc_data->reg_offset;
bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
- u32 xcsr, count = 100;
+ int adir = tx ? RX : TX;
+ int dir = tx ? TX : RX;
+ u32 xcsr;
/*
* Asynchronous mode: Clear SYNC for both Tx and Rx.
@@ -548,10 +600,22 @@ static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx, ofs),
FSL_SAI_CSR_FRDE, FSL_SAI_CSR_FRDE);
- regmap_update_bits(sai->regmap, FSL_SAI_RCSR(ofs),
- FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
- regmap_update_bits(sai->regmap, FSL_SAI_TCSR(ofs),
+ regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx, ofs),
FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
+ /*
+ * Enable the opposite direction for synchronous mode
+ * 1. Tx sync with Rx: only set RE for Rx; set TE & RE for Tx
+ * 2. Rx sync with Tx: only set TE for Tx; set RE & TE for Rx
+ *
+ * RM recommends to enable RE after TE for case 1 and to enable
+ * TE after RE for case 2, but we here may not always guarantee
+ * that happens: "arecord 1.wav; aplay 2.wav" in case 1 enables
+ * TE after RE, which is against what RM recommends but should
+ * be safe to do, judging by years of testing results.
+ */
+ if (fsl_sai_dir_is_synced(sai, adir))
+ regmap_update_bits(sai->regmap, FSL_SAI_xCSR((!tx), ofs),
+ FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx, ofs),
FSL_SAI_CSR_xIE_MASK, FSL_SAI_FLAGS);
@@ -566,43 +630,23 @@ static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
/* Check if the opposite FRDE is also disabled */
regmap_read(sai->regmap, FSL_SAI_xCSR(!tx, ofs), &xcsr);
- if (!(xcsr & FSL_SAI_CSR_FRDE)) {
- /* Disable both directions and reset their FIFOs */
- regmap_update_bits(sai->regmap, FSL_SAI_TCSR(ofs),
- FSL_SAI_CSR_TERE, 0);
- regmap_update_bits(sai->regmap, FSL_SAI_RCSR(ofs),
- FSL_SAI_CSR_TERE, 0);
-
- /* TERE will remain set till the end of current frame */
- do {
- udelay(10);
- regmap_read(sai->regmap,
- FSL_SAI_xCSR(tx, ofs), &xcsr);
- } while (--count && xcsr & FSL_SAI_CSR_TERE);
-
- regmap_update_bits(sai->regmap, FSL_SAI_TCSR(ofs),
- FSL_SAI_CSR_FR, FSL_SAI_CSR_FR);
- regmap_update_bits(sai->regmap, FSL_SAI_RCSR(ofs),
- FSL_SAI_CSR_FR, FSL_SAI_CSR_FR);
-
- /*
- * For sai master mode, after several open/close sai,
- * there will be no frame clock, and can't recover
- * anymore. Add software reset to fix this issue.
- * This is a hardware bug, and will be fix in the
- * next sai version.
- */
- if (!sai->is_slave_mode) {
- /* Software Reset for both Tx and Rx */
- regmap_write(sai->regmap, FSL_SAI_TCSR(ofs),
- FSL_SAI_CSR_SR);
- regmap_write(sai->regmap, FSL_SAI_RCSR(ofs),
- FSL_SAI_CSR_SR);
- /* Clear SR bit to finish the reset */
- regmap_write(sai->regmap, FSL_SAI_TCSR(ofs), 0);
- regmap_write(sai->regmap, FSL_SAI_RCSR(ofs), 0);
- }
- }
+
+ /*
+ * If opposite stream provides clocks for synchronous mode and
+ * it is inactive, disable it before disabling the current one
+ */
+ if (fsl_sai_dir_is_synced(sai, adir) && !(xcsr & FSL_SAI_CSR_FRDE))
+ fsl_sai_config_disable(sai, adir);
+
+ /*
+ * Disable current stream if either of:
+ * 1. current stream doesn't provide clocks for synchronous mode
+ * 2. current stream provides clocks for synchronous mode but no
+ * more stream is active.
+ */
+ if (!fsl_sai_dir_is_synced(sai, dir) || !(xcsr & FSL_SAI_CSR_FRDE))
+ fsl_sai_config_disable(sai, dir);
+
break;
default:
return -EINVAL;
--
2.27.0