From 300689fb04b3f23c1ac1abfe960b48ec414df597 Mon Sep 17 00:00:00 2001
From: Sascha Hauer <s.hauer@pengutronix.de>
Date: Tue, 1 Mar 2022 12:34:46 +0100
Subject: [PATCH] ASoC: soc-generic-dmaengine-pcm: set period_bytes_min based on maxburst
Git-commit: 300689fb04b3f23c1ac1abfe960b48ec414df597
Patch-mainline: v5.18-rc1
References: jsc#PED-850

In dmaengine_pcm_set_runtime_hwparams() period_bytes_min is hardcoded to
256. For some applications that may be too big. This patch changes that
to calculate the value based on dma_data->maxburst. The correct value
would be maxburst multiplied by the address width of the hardware FIFO.
Unfortunately the address width is dynamically calculated based on the
stream parameters and is not known at open time, so the worst case
is chosen here which is 8 bytes, the maximum that is supported by
dmaengine drivers.
Not all drivers may set a maxburst value, so we fall back to the
previously used hardcoded value of 256 bytes.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Link: https://lore.kernel.org/r/20220301113446.1053171-1-s.hauer@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 sound/soc/soc-generic-dmaengine-pcm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
index 8659cb1794f1..285441d6aeed 100644
--- a/sound/soc/soc-generic-dmaengine-pcm.c
+++ b/sound/soc/soc-generic-dmaengine-pcm.c
@@ -132,7 +132,9 @@ dmaengine_pcm_set_runtime_hwparams(struct snd_soc_component *component,
 			SNDRV_PCM_INFO_INTERLEAVED;
 	hw.periods_min = 2;
 	hw.periods_max = UINT_MAX;
-	hw.period_bytes_min = 256;
+	hw.period_bytes_min = dma_data->maxburst * DMA_SLAVE_BUSWIDTH_8_BYTES;
+	if (!hw.period_bytes_min)
+		hw.period_bytes_min = 256;
 	hw.period_bytes_max = dma_get_max_seg_size(dma_dev);
 	hw.buffer_bytes_max = SIZE_MAX;
 	hw.fifo_size = dma_data->fifo_size;
-- 
2.35.3