[PATCH v2 1/3] remoteproc: imx_dsp_rproc: Skip RP_MBOX_SUSPEND_SYSTEM when mailbox TX channel is uninitialized

[Iuliana Prodan (OSS)]

From: Iuliana Prodan <iuliana.prodan at nxp.com>

Firmwares that do not use mailbox communication (e.g., the hello_world
sample) leave priv->tx_ch as NULL. The current suspend logic
unconditionally sends RP_MBOX_SUSPEND_SYSTEM, which is invalid without
an initialized TX channel.

Detect the no_mailboxes case early and skip sending the suspend
message. Instead, proceed directly to the runtime PM suspend path,
which is the correct behavior for firmwares that cannot respond to
mailbox requests.

Signed-off-by: Iuliana Prodan <iuliana.prodan at nxp.com>
---
Changes since v1:
- Wrapped commit message to 75 characters
- Changed dev_err to dev_dbg since this case is normal behavior
---
 drivers/remoteproc/imx_dsp_rproc.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/remoteproc/imx_dsp_rproc.c b/drivers/remoteproc/imx_dsp_rproc.c
index 5130a35214c9..f51deaacc700 100644
--- a/drivers/remoteproc/imx_dsp_rproc.c
+++ b/drivers/remoteproc/imx_dsp_rproc.c
@@ -1242,6 +1242,15 @@ static int imx_dsp_suspend(struct device *dev)
 	if (rproc->state != RPROC_RUNNING)
 		goto out;
 
+	/*
+	 * No channel available for sending messages;
+	 * indicates no mailboxes present, so trigger PM runtime suspend
+	 */
+	if (!priv->tx_ch) {
+		dev_dbg(dev, "No initialized mbox tx channel, suspend directly.\n");
+		goto out;
+	}
+
 	reinit_completion(&priv->pm_comp);
 
 	/* Tell DSP that suspend is happening */
-- 
2.25.1