linux-kernel - [PATCH v3 05/20] ASoC: tegra20: spdif: Set FIFO trigger level

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Date:   Thu,  2 Dec 2021 19:23:26 +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>, Rob Herring <robh+dt@...nel.org>
Cc:     linux-tegra@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: [PATCH v3 05/20] ASoC: tegra20: spdif: Set FIFO trigger level

FIFO trigger level must be not less than the size of DMA burst, otherwise
audio will be played x4 faster that it should be because part of the DMA
data will be dropped on FIFO input buffer overflow.

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 7751575cd6d6..6f0570cde964 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