ASoC: rockchip: i2s_tdm: Re-add the set_sysclk callback

In commit
9e2ab4b18ebd ("ASoC: rockchip: i2s-tdm: Fix inaccurate sampling rates"),
the set_sysclk callback was removed as considered unused as the mclk rate
can be set in the hw_params callback.
The difference between hw_params and set_sysclk is that the former is
called with the audio sampling rate set in the params (e.g.: 48000 Hz)
while the latter is called with a clock rate already computed with
sampling_rate * mclk-fs (e.g.: 48000 * 256)

For HDMI audio using the Rockchip I2S TDM driver, the mclk-fs value must
be set to 128 instead of the default 256, and that value is set in the
device tree at the machine driver level (like a simple-audio-card
compatible node).
Therefore, the i2s_tdm driver has no idea that another mclk-fs value can
be configured and simply computes the mclk rate in the hw_params callback
with DEFAULT_MCLK_FS * params_rate(params), which is wrong for HDMI
audio.

Re-add the set_sysclk callback so that the mclk rate is computed by the
machine driver which has the correct mclk-fs value set in its device tree
node.

Fixes: 9e2ab4b18ebd ("ASoC: rockchip: i2s-tdm: Fix inaccurate sampling rates")
Signed-off-by: Detlev Casanova <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/rockchip/rockchip_i2s_tdm.c

···
 
 #define DRV_NAME "rockchip-i2s-tdm"
 
-#define DEFAULT_MCLK_FS				256
 #define CH_GRP_MAX				4  /* The max channel 8 / 2 */
 #define MULTIPLEX_CH_MAX			10
 
···
 	bool has_playback;
 	bool has_capture;
 	struct snd_soc_dai_driver *dai;
+	unsigned int mclk_rx_freq;
+	unsigned int mclk_tx_freq;
 };
 
 static int to_ch_num(unsigned int val)
···
 	return 0;
 }
 
+static int rockchip_i2s_tdm_set_sysclk(struct snd_soc_dai *cpu_dai, int stream,
+				       unsigned int freq, int dir)
+{
+	struct rk_i2s_tdm_dev *i2s_tdm = to_info(cpu_dai);
+
+	if (i2s_tdm->clk_trcm) {
+		i2s_tdm->mclk_tx_freq = freq;
+		i2s_tdm->mclk_rx_freq = freq;
+	} else {
+		if (stream == SNDRV_PCM_STREAM_PLAYBACK)
+			i2s_tdm->mclk_tx_freq = freq;
+		else
+			i2s_tdm->mclk_rx_freq = freq;
+	}
+
+	dev_dbg(i2s_tdm->dev, "The target mclk_%s freq is: %d\n",
+		stream ? "rx" : "tx", freq);
+
+	return 0;
+}
+
 static int rockchip_i2s_tdm_hw_params(struct snd_pcm_substream *substream,
 				      struct snd_pcm_hw_params *params,
 				      struct snd_soc_dai *dai)
···
 
 		if (i2s_tdm->clk_trcm == TRCM_TX) {
 			mclk = i2s_tdm->mclk_tx;
+			mclk_rate = i2s_tdm->mclk_tx_freq;
 		} else if (i2s_tdm->clk_trcm == TRCM_RX) {
 			mclk = i2s_tdm->mclk_rx;
+			mclk_rate = i2s_tdm->mclk_rx_freq;
 		} else if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 			mclk = i2s_tdm->mclk_tx;
+			mclk_rate = i2s_tdm->mclk_tx_freq;
 		} else {
 			mclk = i2s_tdm->mclk_rx;
+			mclk_rate = i2s_tdm->mclk_rx_freq;
 		}
 
-		err = clk_set_rate(mclk, DEFAULT_MCLK_FS * params_rate(params));
+		err = clk_set_rate(mclk, mclk_rate);
 		if (err)
 			return err;
 
···
 	.hw_params = rockchip_i2s_tdm_hw_params,
 	.set_bclk_ratio	= rockchip_i2s_tdm_set_bclk_ratio,
 	.set_fmt = rockchip_i2s_tdm_set_fmt,
+	.set_sysclk = rockchip_i2s_tdm_set_sysclk,
 	.set_tdm_slot = rockchip_dai_tdm_slot,
 	.trigger = rockchip_i2s_tdm_trigger,
 };