From patchwork series 377117

https://patchwork.ozlabs.org//project/linuxppc-dev/list/?series=377117

Documentation/devicetree/bindings/sound/sound-card-common.yaml

@@ -17,6 +17,20 @@ properties:
       pair of strings, the first being the connection's sink, the second
       being the connection's source.
 
+  lpa-widgets:
+    $ref: /schemas/types.yaml#/definitions/non-unique-string-array
+    description: |
+      A list of DAPM endpoints which mark paths between these endpoints should
+      not be disabled when system enters in suspend state. LPA means low power
+      audio case. For example on asymmetric multiprocessor, there are Cortex-A
+      core and Cortex-M core, Linux is running on Cortex-A core, RTOS or other
+      OS is running on Cortex-M core. The audio hardware devices can be
+      controlled by Cortex-M. LPA can be explained as a mechanism that Cortex-A
+      allocates a large buffer and fill audio data, then Cortex-A can enter
+      into suspend for the purpose of power saving. Cortex-M continues to play
+      the sound during suspend phase of Cortex-A. LPA requires some audio paths
+      still enabled when Cortex-A enters into suspend.
+
   model:
     $ref: /schemas/types.yaml#/definitions/string
     description: User specified audio sound card name

sound/soc/fsl/imx-rpmsg.c

@@ -20,8 +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),
@@ -38,6 +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,
+									"lpa-widgets");
+				for (i = 0; i < num_widgets; i++) {
+					of_property_read_string_index(data->card.dev->of_node,
+								      "lpa-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;
 
@@ -137,6 +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;