echoplayer: pcm: increase SAI FIFO buffer depth

commit da53cc0f1425c6f62a607a66d563359879eb5d3a
Author: Aidan MacDonald <[email protected]>
Date:   Tue Mar 24 00:04:16 2026 +0000

    echoplayer: pcm: increase SAI FIFO buffer depth
    
    Change the SAI FIFO threshold so that it is always
    kept topped up at maximum; DMA needs to do single
    transfers to the peripheral now. Ignore FEIF errors
    since they seem to occur constantly with this setup
    (though it's not exactly clear why this happens).
    
    FEIF only indicates that the SAI made a DMA request
    while the DMA FIFO is empty, which isn't a fatal error.
    The DMA channel will simply service the request when
    it is ready.
    
    Keeping the SAI FIFO constantly full increases the
    overall timing margin before underrun so losing the
    FEIF info isn't a big deal in practice.
    
    Change-Id: I16eb1cbb17039db76938bd86c4921b8060c83556

diff --git a/firmware/target/arm/stm32/debug-stm32h7.c b/firmware/target/arm/stm32/debug-stm32h7.c
index f8cd7200c3..4002876e28 100644
--- a/firmware/target/arm/stm32/debug-stm32h7.c
+++ b/firmware/target/arm/stm32/debug-stm32h7.c
@@ -89,8 +89,6 @@ static bool swd_menu(void)
 #if defined(ECHO_R1)
 extern volatile int pcm_sai_xrun_count;
 extern volatile int pcm_dma_teif_count;
-extern volatile int pcm_dma_dmeif_count;
-extern volatile int pcm_dma_feif_count;
 
 struct pcmdebug_counter
 {
@@ -102,8 +100,6 @@ static const struct pcmdebug_counter pcmdebug_counters[] =
 {
     {"SAI xrun count",  &pcm_sai_xrun_count},
     {"DMA TEIF count",  &pcm_dma_teif_count},
-    {"DMA DMEIF count", &pcm_dma_dmeif_count},
-    {"DMA FEIF count",  &pcm_dma_feif_count},
 };
 
 static int pcmdebug_menu_action_cb(int action, struct gui_synclist *lists)
diff --git a/firmware/target/arm/stm32/echoplayer/pcm-echoplayer.c b/firmware/target/arm/stm32/echoplayer/pcm-echoplayer.c
index c1d457ef8d..1867b21de0 100644
--- a/firmware/target/arm/stm32/echoplayer/pcm-echoplayer.c
+++ b/firmware/target/arm/stm32/echoplayer/pcm-echoplayer.c
@@ -36,19 +36,16 @@
 # define PCM_NATIVE_SAMPLE_SIZE     4
 # define DMA_PSIZE_VAL              BV_DMA_CHN_CR_PSIZE_32BIT
 # define SAI_DSIZE_VAL              BV_SAI_SUBBLOCK_CR1_DS_32BIT
-# define SAI_FIFO_THRESH            BV_SAI_SUBBLOCK_CR2_FTH_QUARTER
 # define SAI_FRL_VAL                64
 #elif PCM_NATIVE_BITDEPTH == 24
 # define PCM_NATIVE_SAMPLE_SIZE     4
 # define DMA_PSIZE_VAL              BV_DMA_CHN_CR_PSIZE_32BIT
 # define SAI_DSIZE_VAL              BV_SAI_SUBBLOCK_CR1_DS_24BIT
-# define SAI_FIFO_THRESH            BV_SAI_SUBBLOCK_CR2_FTH_QUARTER
 # define SAI_FRL_VAL                64
 #elif PCM_NATIVE_BITDEPTH == 16
 # define PCM_NATIVE_SAMPLE_SIZE     2
 # define DMA_PSIZE_VAL              BV_DMA_CHN_CR_PSIZE_16BIT
 # define SAI_DSIZE_VAL              BV_SAI_SUBBLOCK_CR1_DS_16BIT
-# define SAI_FIFO_THRESH            BV_SAI_SUBBLOCK_CR2_FTH_HALF
 # define SAI_FRL_VAL                32
 #else
 # error "Unsupported PCM bit depth"
@@ -67,8 +64,6 @@ static int pcm_last_freq = -1;
 
 volatile int pcm_sai_xrun_count;
 volatile int pcm_dma_teif_count;
-volatile int pcm_dma_dmeif_count;
-volatile int pcm_dma_feif_count;
 
 static void play_dma_start(const void *addr, size_t size)
 {
@@ -105,7 +100,7 @@ static void sai_init(void)
     /* Configure DMA1 channel 0 */
     reg_writelf(dma1_ch0, DMA_CHN_CR,
                 MBURST_V(INCR4),        /* 32-bit x 4 burst = 16 bytes */
-                PBURST_V(INCR4),        /* (16|32)-bit x 4 burst = 8-16 bytes */
+                PBURST_V(SINGLE),       /* (16|32)-bit x 4 burst = 8-16 bytes */
                 TRBUFF(0),              /* bufferable mode not used for SAI */
                 DBM(0),                 /* double buffer mode off */
                 PL_V(VERYHIGH),         /* highest priority */
@@ -117,10 +112,8 @@ static void sai_init(void)
                 DIR_V(MEM_TO_PERIPH),   /* read from memory, write to SAI */
                 PFCTRL_V(DMA),          /* DMA is flow controller */
                 TCIE(1),                /* transfer complete interrupt */
-                TEIE(1),                /* transfer error interrupt */
-                DMEIE(1));              /* direct mode error interrupt */
+                TEIE(1));               /* transfer error interrupt */
     reg_writelf(dma1_ch0, DMA_CHN_FCR,
-                FEIE(1),                /* fifo error interrupt */
                 DMDIS(1),               /* enable fifo mode */
                 FTH_V(FULL));           /* fifo threshold = 4 words */
 
@@ -146,7 +139,7 @@ static void sai_init(void)
                 MUTEVAL_V(ZERO_SAMPLE),         /* send zero sample on mute */
                 MUTE(1),                        /* mute output initially */
                 TRIS(0),                        /* don't tri-state outputs */
-                FTH(SAI_FIFO_THRESH));          /* fifo threshold (2 or 4 samples) */
+                FTH_V(FULL));                   /* fifo threshold (2 or 4 samples) */
     reg_writelf(sai1a, SAI_SUBBLOCK_FRCR,
                 FSOFF(1), FSPOL(0), FSDEF(1),   /* I2S format */
                 FSALL(SAI_FRL_VAL/2 - 1),       /* FS active for half the frame */
@@ -336,22 +329,12 @@ void dma1_ch0_irq_handler(void)
     size_t size;
 
     if (reg_vreadf(lisr, DMA_LISR, TEIF0))
-        pcm_dma_teif_count++;
-
-    if (reg_vreadf(lisr, DMA_LISR, DMEIF0))
-        pcm_dma_dmeif_count++;
-
-    if (reg_vreadf(lisr, DMA_LISR, FEIF0))
-        pcm_dma_feif_count++;
-
-    if (reg_vreadf(lisr, DMA_LISR, TEIF0) ||
-        reg_vreadf(lisr, DMA_LISR, DMEIF0) ||
-        reg_vreadf(lisr, DMA_LISR, FEIF0))
     {
-        reg_assignlf(dma1, DMA_LIFCR, TEIF0(1), DMEIF0(1), FEIF0(1));
-        reg_writelf(dma1_ch0, DMA_CHN_CR, EN(0));
+        pcm_dma_teif_count++;
+        reg_assignlf(dma1, DMA_LIFCR, TEIF0(1));
 
-        pcm_play_dma_status_callback(PCM_DMAST_ERR_DMA);
+        /* TODO: this case may need additional handling */
+        pcm_play_dma_complete_callback(PCM_DMAST_ERR_DMA, NULL, NULL);
     }
     else if (reg_vreadf(lisr, DMA_LISR, TCIF0))
     {
-- 
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