Set best burst size tradeoff for 8, 16, 32 bits transfers.
Signed-off-by: olivier moysan olivier.moysan@st.com --- sound/soc/stm/stm32_sai_sub.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-)
diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c index fdc1891..2af397d 100644 --- a/sound/soc/stm/stm32_sai_sub.c +++ b/sound/soc/stm/stm32_sai_sub.c @@ -445,12 +445,16 @@ static int stm32_sai_set_config(struct snd_soc_dai *cpu_dai, { struct stm32_sai_sub_data *sai = snd_soc_dai_get_drvdata(cpu_dai); int cr1, cr1_mask, ret; - int fth = STM_SAI_FIFO_TH_HALF;
- /* FIFO config */ + /* + * DMA bursts increment is set to 4 words. + * SAI fifo threshold is set to half fifo, to keep enough space + * for DMA incoming bursts. + */ regmap_update_bits(sai->regmap, STM_SAI_CR2_REGX, SAI_XCR2_FFLUSH | SAI_XCR2_FTH_MASK, - SAI_XCR2_FFLUSH | SAI_XCR2_FTH_SET(fth)); + SAI_XCR2_FFLUSH | + SAI_XCR2_FTH_SET(STM_SAI_FIFO_TH_HALF));
/* Mode, data format and channel config */ cr1_mask = SAI_XCR1_DS_MASK; @@ -479,10 +483,6 @@ static int stm32_sai_set_config(struct snd_soc_dai *cpu_dai, return ret; }
- /* DMA config */ - sai->dma_params.maxburst = STM_SAI_FIFO_SIZE * fth / sizeof(u32); - snd_soc_dai_set_dma_data(cpu_dai, substream, (void *)&sai->dma_params); - return 0; }
@@ -726,7 +726,12 @@ static int stm32_sai_dai_probe(struct snd_soc_dai *cpu_dai) int cr1 = 0, cr1_mask;
sai->dma_params.addr = (dma_addr_t)(sai->phys_addr + STM_SAI_DR_REGX); - sai->dma_params.maxburst = 1; + /* + * DMA supports 4, 8 or 16 burst sizes. Burst size 4 is the best choice, + * as it allows bytes, half-word and words transfers. (See DMA fifos + * constraints). + */ + sai->dma_params.maxburst = 4; /* Buswidth will be set by framework at runtime */ sai->dma_params.addr_width = DMA_SLAVE_BUSWIDTH_UNDEFINED;