linux-kernel - Re: [PATCH 2/4] ASoC: tegra: Add a TDM configuration callback

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Message-ID: <2392df6f-12bc-74fe-ec0f-50dbb7b9a33a@nvidia.com>
Date:   Mon, 30 Jul 2018 10:31:16 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Jorge Sanjuan <jorge.sanjuan@...ethink.co.uk>,
        <lgirdwood@...il.com>, <broonie@...nel.org>
CC:     <thierry.reding@...il.com>, <alsa-devel@...a-project.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-kernel@...ts.codethink.co.uk>
Subject: Re: [PATCH 2/4] ASoC: tegra: Add a TDM configuration callback


On 27/07/18 13:59, Jorge Sanjuan wrote:
> From: Edward Cragg <edward.cragg@...ethink.co.uk>
> 
> Add a callback to configure TDM settings for the Tegra30
> I2S ASoC 'platform' driver.
> 
> Signed-off-by: Ben Dooks <ben.dooks@...ethink.co.uk>
> Signed-off-by: Edward Cragg <edward.cragg@...ethink.co.uk>
> [jorge.sanjuan@...ethink.co.uk: Style fixes]
> Signed-off-by: Jorge Sanjuan <jorge.sanjuan@...ethink.co.uk>
> ---
>  sound/soc/tegra/tegra30_i2s.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/sound/soc/tegra/tegra30_i2s.c b/sound/soc/tegra/tegra30_i2s.c
> index 0b176ea24914..ff1996f215ed 100644
> --- a/sound/soc/tegra/tegra30_i2s.c
> +++ b/sound/soc/tegra/tegra30_i2s.c
> @@ -265,6 +265,39 @@ static int tegra30_i2s_trigger(struct snd_pcm_substream *substream, int cmd,
>  	return 0;
>  }
>  
> +static int tegra30_i2s_set_tdm(struct snd_soc_dai *dai,
> +			       unsigned int tx_mask, unsigned int rx_mask,
> +			       int slots, int slot_width)
> +{
> +	struct tegra30_i2s *i2s = snd_soc_dai_get_drvdata(dai);
> +	unsigned int mask = 0, val = 0;
> +
> +	dev_dbg(dai->dev, "%s: setting TDM: tx_mask: 0x%08x rx_mask: 0x%08x"
> +		"slots: 0x%08x width: %d\n",
> +		__func__, tx_mask, rx_mask, slots, slot_width);
> +
> +	/* Set up slots and tx/rx masks */
> +	mask = TEGRA30_I2S_SLOT_CTRL_TOTAL_SLOTS_MASK |
> +	       TEGRA30_I2S_SLOT_CTRL_RX_SLOT_ENABLES_MASK |
> +	       TEGRA30_I2S_SLOT_CTRL_TX_SLOT_ENABLES_MASK;
> +
> +	val = (tx_mask << TEGRA30_I2S_SLOT_CTRL_TX_SLOT_ENABLES_SHIFT) |
> +	      (rx_mask << TEGRA30_I2S_SLOT_CTRL_RX_SLOT_ENABLES_SHIFT) |
> +	      ((slots - 1) << TEGRA30_I2S_SLOT_CTRL_TOTAL_SLOTS_SHIFT);
> +
> +	pm_runtime_get_sync(dai->dev);
> +	regmap_update_bits(i2s->regmap, TEGRA30_I2S_SLOT_CTRL, mask, val);
> +
> +	/* Set FSYNC width */
> +	mask = TEGRA30_I2S_CH_CTRL_FSYNC_WIDTH_MASK;
> +	val = (slot_width - 1) << TEGRA30_I2S_CH_CTRL_FSYNC_WIDTH_SHIFT;
> +
> +	regmap_update_bits(i2s->regmap, TEGRA30_I2S_CH_CTRL, mask, val);
> +	pm_runtime_put(dai->dev);
> +
> +	return 0;
> +}
> +

Looking at the TRM for Tegra30 and Tegra124, the I2S_SLOT_CTRL register is different
where for Tegra30 the 'TOTAL_SLOTS' bit are in position 18:16, but for Tegra124 they
are 3:0. This driver supports both Tegra30 and Tegra124, and so this function will
need to handle both.

It can be quite common for the fsync-width for DSP modes to be a single clock and so 
I am not sure that is makes sense to set this here always to the slot width. It maybe
worth considering add a DT property for specifying the fsync width.

Cheers
Jon

-- 
nvpublic