ASoC: Intel: cht_bsw_max98090: add support for Baytrail

Distributions such as Fedora, Ubuntu and Gallium don't currently
have a means to support Baytrail Chromebooks and other platforms
with the same build [1][2] due to incompatible platform drivers.

Add MCLK management to reuse this machine driver for Baytrail
platforms and solve this coexistence problem at last. UCM files are
provided at [3] and will eventually be submitted to the new repo.

The legacy byt-max98090 machine driver is still maintained but can
only be used when the other Atom/DPCM driver is not compiled in, or
when users don't want to configure extra mixers required by the
Atom/sst driver.

Tested on Lenovo 100s Baytrail Chromebook w/ Mr. Chromebox BOOT_STUB
firmware and Acer R11 Cherrytrail Chromebook

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1335196
[2] http://mailman.alsa-project.org/pipermail/alsa-devel/2016-August/
111641.html
[3] https://github.com/plbossart/UCM/tree/master/byt-max98090

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Acked-By: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/boards/cht_bsw_max98090_ti.c

@@ -23,6 +23,7 @@
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/acpi.h>
+#include <linux/clk.h>
 #include <sound/pcm.h>
 #include <sound/pcm_params.h>
 #include <sound/soc.h>
@@ -35,15 +36,60 @@
 #define CHT_CODEC_DAI	"HiFi"
 
 struct cht_mc_private {
+	struct clk *mclk;
 	struct snd_soc_jack jack;
 	bool ts3a227e_present;
 };
 
+static inline struct snd_soc_dai *cht_get_codec_dai(struct snd_soc_card *card)
+{
+	struct snd_soc_pcm_runtime *rtd;
+
+	list_for_each_entry(rtd, &card->rtd_list, list) {
+		if (!strncmp(rtd->codec_dai->name, CHT_CODEC_DAI,
+			     strlen(CHT_CODEC_DAI)))
+			return rtd->codec_dai;
+	}
+	return NULL;
+}
+
+static int platform_clock_control(struct snd_soc_dapm_widget *w,
+					  struct snd_kcontrol *k, int  event)
+{
+	struct snd_soc_dapm_context *dapm = w->dapm;
+	struct snd_soc_card *card = dapm->card;
+	struct snd_soc_dai *codec_dai;
+	struct cht_mc_private *ctx = snd_soc_card_get_drvdata(card);
+	int ret;
+
+	codec_dai = cht_get_codec_dai(card);
+	if (!codec_dai) {
+		dev_err(card->dev, "Codec dai not found; Unable to set platform clock\n");
+		return -EIO;
+	}
+
+	if (SND_SOC_DAPM_EVENT_ON(event)) {
+		ret = clk_prepare_enable(ctx->mclk);
+		if (ret < 0) {
+			dev_err(card->dev,
+				"could not configure MCLK state");
+			return ret;
+		}
+	} else {
+		clk_disable_unprepare(ctx->mclk);
+	}
+
+	return 0;
+}
+
 static const struct snd_soc_dapm_widget cht_dapm_widgets[] = {
 	SND_SOC_DAPM_HP("Headphone", NULL),
 	SND_SOC_DAPM_MIC("Headset Mic", NULL),
 	SND_SOC_DAPM_MIC("Int Mic", NULL),
 	SND_SOC_DAPM_SPK("Ext Spk", NULL),
+	SND_SOC_DAPM_SUPPLY("Platform Clock", SND_SOC_NOPM, 0, 0,
+			    platform_clock_control, SND_SOC_DAPM_PRE_PMU |
+			    SND_SOC_DAPM_POST_PMD),
 };
 
 static const struct snd_soc_dapm_route cht_audio_map[] = {
@@ -60,6 +106,10 @@ static const struct snd_soc_dapm_route cht_audio_map[] = {
 	{"codec_in0", NULL, "ssp2 Rx" },
 	{"codec_in1", NULL, "ssp2 Rx" },
 	{"ssp2 Rx", NULL, "HiFi Capture"},
+	{"Headphone", NULL, "Platform Clock"},
+	{"Headset Mic", NULL, "Platform Clock"},
+	{"Int Mic", NULL, "Platform Clock"},
+	{"Ext Spk", NULL, "Platform Clock"},
 };
 
 static const struct snd_kcontrol_new cht_mc_controls[] = {
@@ -141,6 +191,25 @@ static int cht_codec_init(struct snd_soc_pcm_runtime *runtime)
 	if (ctx->ts3a227e_present)
 		snd_soc_jack_notifier_register(jack, &cht_jack_nb);
 
+	/*
+	 * The firmware might enable the clock at
+	 * boot (this information may or may not
+	 * be reflected in the enable clock register).
+	 * To change the rate we must disable the clock
+	 * first to cover these cases. Due to common
+	 * clock framework restrictions that do not allow
+	 * to disable a clock that has not been enabled,
+	 * we need to enable the clock first.
+	 */
+	ret = clk_prepare_enable(ctx->mclk);
+	if (!ret)
+		clk_disable_unprepare(ctx->mclk);
+
+	ret = clk_set_rate(ctx->mclk, CHT_PLAT_CLK_3_HZ);
+
+	if (ret)
+		dev_err(runtime->dev, "unable to set MCLK rate\n");
+
 	return ret;
 }
 
@@ -294,6 +363,15 @@ static int snd_cht_mc_probe(struct platform_device *pdev)
 	/* register the soc card */
 	snd_soc_card_cht.dev = &pdev->dev;
 	snd_soc_card_set_drvdata(&snd_soc_card_cht, drv);
+
+	drv->mclk = devm_clk_get(&pdev->dev, "pmc_plt_clk_3");
+	if (IS_ERR(drv->mclk)) {
+		dev_err(&pdev->dev,
+			"Failed to get MCLK from pmc_plt_clk_3: %ld\n",
+			PTR_ERR(drv->mclk));
+		return PTR_ERR(drv->mclk);
+	}
+
 	ret_val = devm_snd_soc_register_card(&pdev->dev, &snd_soc_card_cht);
 	if (ret_val) {
 		dev_err(&pdev->dev,