remoteproc: imx_dsp_rproc: Add module parameter to ignore ready flag from remote processor

There are cases when we want to test a simple "hello world"
application on the DSP and we don't have IPC between the cores.
Therefore, do not wait for a confirmation from the remote processor
at start.

Added "no_mailboxes" flag while inserting the module to not initialize
any mailboxes, and so ignore remote processor reply after start.
By default, this is off - do not ignore reply from rproc.
Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Link: https://lore.kernel.org/r/20230217094124.9440-1-iuliana.prodan@oss.nxp.com
[Fixed checkpatch warning]
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/remoteproc/imx_dsp_rproc.c

@@ -28,6 +28,14 @@
 
 #define DSP_RPROC_CLK_MAX			5
 
+/*
+ * Module parameters
+ */
+static unsigned int no_mailboxes;
+module_param_named(no_mailboxes, no_mailboxes, int, 0644);
+MODULE_PARM_DESC(no_mailboxes,
+		 "There is no mailbox between cores, so ignore remote proc reply after start, default is 0 (off).");
+
 #define REMOTE_IS_READY				BIT(0)
 #define REMOTE_READY_WAIT_MAX_RETRIES		500
 
@@ -172,6 +180,9 @@ static const struct imx_rproc_att imx_dsp_rproc_att_imx8ulp[] = {
 	{ 0x30000000, 0x90000000, 0x10000000, 0},
 };
 
+/* Initialize the mailboxes between cores, if exists */
+static int (*imx_dsp_rproc_mbox_init)(struct imx_dsp_rproc *priv);
+
 /* Reset function for DSP on i.MX8MP */
 static int imx8mp_dsp_reset(struct imx_dsp_rproc *priv)
 {
@@ -492,12 +503,12 @@ static void imx_dsp_rproc_rxdb_callback(struct mbox_client *cl, void *data)
 }
 
 /**
- * imx_dsp_rproc_mbox_init() - request mailbox channels
+ * imx_dsp_rproc_mbox_alloc() - request mailbox channels
  * @priv: private data pointer
  *
  * Request three mailbox channels (tx, rx, rxdb).
  */
-static int imx_dsp_rproc_mbox_init(struct imx_dsp_rproc *priv)
+static int imx_dsp_rproc_mbox_alloc(struct imx_dsp_rproc *priv)
 {
 	struct device *dev = priv->rproc->dev.parent;
 	struct mbox_client *cl;
@@ -560,6 +571,18 @@ static int imx_dsp_rproc_mbox_init(struct imx_dsp_rproc *priv)
 	return ret;
 }
 
+/*
+ * imx_dsp_rproc_mbox_no_alloc()
+ *
+ * Empty function for no mailbox between cores
+ *
+ * Always return 0
+ */
+static int imx_dsp_rproc_mbox_no_alloc(struct imx_dsp_rproc *priv)
+{
+	return 0;
+}
+
 static void imx_dsp_rproc_free_mbox(struct imx_dsp_rproc *priv)
 {
 	mbox_free_channel(priv->tx_ch);
@@ -903,6 +926,11 @@ static int imx_dsp_rproc_probe(struct platform_device *pdev)
 	priv->rproc = rproc;
 	priv->dsp_dcfg = dsp_dcfg;
 
+	if (no_mailboxes)
+		imx_dsp_rproc_mbox_init = imx_dsp_rproc_mbox_no_alloc;
+	else
+		imx_dsp_rproc_mbox_init = imx_dsp_rproc_mbox_alloc;
+
 	dev_set_drvdata(dev, rproc);
 
 	INIT_WORK(&priv->rproc_work, imx_dsp_rproc_vq_work);