linux-kernel - [PATCH v5 04/11] ASoC: tegra20: spdif: Set FIFO trigger level

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Date:   Fri, 17 Dec 2021 20:55:59 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Liam Girdwood <lgirdwood@...il.com>,
        Agneli <poczt@...tonmail.ch>
Cc:     linux-tegra@...r.kernel.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: [PATCH v5 04/11] ASoC: tegra20: spdif: Set FIFO trigger level

FIFO trigger level must be bigger than or equal to the size of DMA burst,
otherwise audio will be played x4 faster than it should be because part of
the DMA data will be dropped on FIFO input buffer overflow.

Acked-by: Thierry Reding <treding@...dia.com>
Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 sound/soc/tegra/tegra20_spdif.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/sound/soc/tegra/tegra20_spdif.c b/sound/soc/tegra/tegra20_spdif.c
index 57a6c576b91f..e45e371edc42 100644
--- a/sound/soc/tegra/tegra20_spdif.c
+++ b/sound/soc/tegra/tegra20_spdif.c
@@ -69,6 +69,14 @@ static int tegra20_spdif_hw_params(struct snd_pcm_substream *substream,
 
 	regmap_update_bits(spdif->regmap, TEGRA20_SPDIF_CTRL, mask, val);
 
+	/*
+	 * FIFO trigger level must be bigger than DMA burst or equal to it,
+	 * otherwise data is discarded on overflow.
+	 */
+	regmap_update_bits(spdif->regmap, TEGRA20_SPDIF_DATA_FIFO_CSR,
+			   TEGRA20_SPDIF_DATA_FIFO_CSR_TX_ATN_LVL_MASK,
+			   TEGRA20_SPDIF_DATA_FIFO_CSR_TX_ATN_LVL_TU4_WORD_FULL);
+
 	switch (params_rate(params)) {
 	case 32000:
 		spdifclock = 4096000;
-- 
2.33.1