[PATCH v5 2/2] ASoC: imx-rpmsg: Force codec power on in low power audio mode

[Chancel Liu <chancel.liu@xxxxxxx>]

Low power audio mode requires binding codec still power on while Acore
enters into suspend so Mcore can continue playback music.

ASoC machine driver acquires DAPM endpoints through reading
"ignore-suspend-widgets" property from DT and then forces the path
between these endpoints ignoring suspend.

If the rpmsg sound card is in low power audio mode, the suspend/resume
callback of binding codec is overridden to disable the suspend/resume.

Signed-off-by: Chancel Liu <chancel.liu@xxxxxxx>
---
 sound/soc/fsl/imx-rpmsg.c | 61 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 59 insertions(+), 2 deletions(-)

diff --git a/sound/soc/fsl/imx-rpmsg.c b/sound/soc/fsl/imx-rpmsg.c
index a0c5c35817dd..e5bd63dab10c 100644
--- a/sound/soc/fsl/imx-rpmsg.c
+++ b/sound/soc/fsl/imx-rpmsg.c
@@ -2,9 +2,8 @@
 // Copyright 2017-2020 NXP
 
 #include <linux/module.h>
-#include <linux/of.h>
+#include <linux/of_platform.h>
 #include <linux/of_reserved_mem.h>
-#include <linux/platform_device.h>
 #include <linux/i2c.h>
 #include <linux/of_gpio.h>
 #include <linux/slab.h>
@@ -21,8 +20,11 @@ struct imx_rpmsg {
 	struct snd_soc_dai_link dai;
 	struct snd_soc_card card;
 	unsigned long sysclk;
+	bool lpa;
 };
 
+static struct dev_pm_ops lpa_pm;
+
 static const struct snd_soc_dapm_widget imx_rpmsg_dapm_widgets[] = {
 	SND_SOC_DAPM_HP("Headphone Jack", NULL),
 	SND_SOC_DAPM_SPK("Ext Spk", NULL),
@@ -39,6 +41,58 @@ static int imx_rpmsg_late_probe(struct snd_soc_card *card)
 	struct device *dev = card->dev;
 	int ret;
 
+	if (data->lpa) {
+		struct snd_soc_component *codec_comp;
+		struct device_node *codec_np;
+		struct device_driver *codec_drv;
+		struct device *codec_dev = NULL;
+
+		codec_np = data->dai.codecs->of_node;
+		if (codec_np) {
+			struct platform_device *codec_pdev;
+			struct i2c_client *codec_i2c;
+
+			codec_i2c = of_find_i2c_device_by_node(codec_np);
+			if (codec_i2c)
+				codec_dev = &codec_i2c->dev;
+			if (!codec_dev) {
+				codec_pdev = of_find_device_by_node(codec_np);
+				if (codec_pdev)
+					codec_dev = &codec_pdev->dev;
+			}
+		}
+		if (codec_dev) {
+			codec_comp = snd_soc_lookup_component_nolocked(codec_dev, NULL);
+			if (codec_comp) {
+				int i, num_widgets;
+				const char *widgets;
+				struct snd_soc_dapm_context *dapm;
+
+				num_widgets = of_property_count_strings(data->card.dev->of_node,
+									"ignore-suspend-widgets");
+				for (i = 0; i < num_widgets; i++) {
+					of_property_read_string_index(data->card.dev->of_node,
+								      "ignore-suspend-widgets",
+								      i, &widgets);
+					dapm = snd_soc_component_get_dapm(codec_comp);
+					snd_soc_dapm_ignore_suspend(dapm, widgets);
+				}
+			}
+			codec_drv = codec_dev->driver;
+			if (codec_drv->pm) {
+				memcpy(&lpa_pm, codec_drv->pm, sizeof(lpa_pm));
+				lpa_pm.suspend = NULL;
+				lpa_pm.resume = NULL;
+				lpa_pm.freeze = NULL;
+				lpa_pm.thaw = NULL;
+				lpa_pm.poweroff = NULL;
+				lpa_pm.restore = NULL;
+				codec_drv->pm = &lpa_pm;
+			}
+			put_device(codec_dev);
+		}
+	}
+
 	if (!data->sysclk)
 		return 0;
 
@@ -138,6 +192,9 @@ static int imx_rpmsg_probe(struct platform_device *pdev)
 		goto fail;
 	}
 
+	if (of_property_read_bool(np, "fsl,enable-lpa"))
+		data->lpa = true;
+
 	data->card.dev = &pdev->dev;
 	data->card.owner = THIS_MODULE;
 	data->card.dapm_widgets = imx_rpmsg_dapm_widgets;
-- 
2.42.0