mailbox: ti-msgmgr: Operate mailbox in polled mode during system suspend

During the system suspend path we must set all queues to operate in
polled mode as it is possible for any protocol built using this mailbox,
such as TISCI, to require communication during the no irq phase of suspend,
and we cannot rely on interrupts there.

Polled mode is implemented by allowing the mailbox user to define an
RX channel as part of the message that is sent which is what gets polled
for a response. If polled mode is enabled, this will immediately be
polled for a response at the end of the mailbox send_data op before
returning success for the data send or timing out if no response is
received.

Finally, to ensure polled mode is always enabled during system suspend,
iterate through all queues to set RX queues to polled mode during system
suspend and disable polled mode for all in the resume handler.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

Author: dgerlach

drivers/mailbox/ti-msgmgr.c

@@ -2,7 +2,7 @@
 /*
  * Texas Instruments' Message Manager Driver
  *
- * Copyright (C) 2015-2017 Texas Instruments Incorporated - https://www.ti.com/
+ * Copyright (C) 2015-2022 Texas Instruments Incorporated - https://www.ti.com/
  *	Nishanth Menon
  */
 
@@ -11,6 +11,7 @@
 #include <linux/device.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/kernel.h>
 #include <linux/mailbox_controller.h>
 #include <linux/module.h>
@@ -100,6 +101,7 @@ struct ti_msgmgr_desc {
  * @queue_ctrl: Queue Control register
  * @chan:	Mailbox channel
  * @rx_buff:	Receive buffer pointer allocated at probe, max_message_size
+ * @polled_rx_mode: Use polling for rx instead of interrupts
  */
 struct ti_queue_inst {
 	char name[30];
@@ -113,6 +115,7 @@ struct ti_queue_inst {
 	void __iomem *queue_ctrl;
 	struct mbox_chan *chan;
 	u32 *rx_buff;
+	bool polled_rx_mode;
 };
 
 /**
@@ -237,6 +240,26 @@ static int ti_msgmgr_queue_rx_data(struct mbox_chan *chan, struct ti_queue_inst
 	return 0;
 }
 
+static int ti_msgmgr_queue_rx_poll_timeout(struct mbox_chan *chan, int timeout_us)
+{
+	struct device *dev = chan->mbox->dev;
+	struct ti_msgmgr_inst *inst = dev_get_drvdata(dev);
+	struct ti_queue_inst *qinst = chan->con_priv;
+	const struct ti_msgmgr_desc *desc = inst->desc;
+	int msg_count;
+	int ret;
+
+	ret = readl_poll_timeout_atomic(qinst->queue_state, msg_count,
+					(msg_count & desc->status_cnt_mask),
+					10, timeout_us);
+	if (ret != 0)
+		return ret;
+
+	ti_msgmgr_queue_rx_data(chan, qinst, desc);
+
+	return 0;
+}
+
 /**
  * ti_msgmgr_queue_rx_interrupt() - Interrupt handler for receive Queue
  * @irq:	Interrupt number
@@ -346,6 +369,17 @@ static bool ti_msgmgr_last_tx_done(struct mbox_chan *chan)
 	return msg_count ? false : true;
 }
 
+static bool ti_msgmgr_chan_has_polled_queue_rx(struct mbox_chan *chan)
+{
+	struct ti_queue_inst *qinst;
+
+	if (!chan)
+		return false;
+
+	qinst = chan->con_priv;
+	return qinst->polled_rx_mode;
+}
+
 /**
  * ti_msgmgr_send_data() - Send data
  * @chan:	Channel Pointer
@@ -363,6 +397,7 @@ static int ti_msgmgr_send_data(struct mbox_chan *chan, void *data)
 	struct ti_msgmgr_message *message = data;
 	void __iomem *data_reg;
 	u32 *word_data;
+	int ret = 0;
 
 	if (WARN_ON(!inst)) {
 		dev_err(dev, "no platform drv data??\n");
@@ -404,7 +439,12 @@ static int ti_msgmgr_send_data(struct mbox_chan *chan, void *data)
 	if (data_reg <= qinst->queue_buff_end)
 		writel(0, qinst->queue_buff_end);
 
-	return 0;
+	/* If we are in polled mode, wait for a response before proceeding */
+	if (ti_msgmgr_chan_has_polled_queue_rx(message->chan_rx))
+		ret = ti_msgmgr_queue_rx_poll_timeout(message->chan_rx,
+						      message->timeout_rx_ms * 1000);
+
+	return ret;
 }
 
 /**
@@ -652,6 +692,54 @@ static int ti_msgmgr_queue_setup(int idx, struct device *dev,
 	return 0;
 }
 
+static int ti_msgmgr_queue_rx_set_polled_mode(struct ti_queue_inst *qinst, bool enable)
+{
+	if (enable) {
+		disable_irq(qinst->irq);
+		qinst->polled_rx_mode = true;
+	} else {
+		enable_irq(qinst->irq);
+		qinst->polled_rx_mode = false;
+	}
+
+	return 0;
+}
+
+static int ti_msgmgr_suspend(struct device *dev)
+{
+	struct ti_msgmgr_inst *inst = dev_get_drvdata(dev);
+	struct ti_queue_inst *qinst;
+	int i;
+
+	/*
+	 * We must switch operation to polled mode now as drivers and the genpd
+	 * layer may make late TI SCI calls to change clock and device states
+	 * from the noirq phase of suspend.
+	 */
+	for (qinst = inst->qinsts, i = 0; i < inst->num_valid_queues; qinst++, i++) {
+		if (!qinst->is_tx)
+			ti_msgmgr_queue_rx_set_polled_mode(qinst, true);
+	}
+
+	return 0;
+}
+
+static int ti_msgmgr_resume(struct device *dev)
+{
+	struct ti_msgmgr_inst *inst = dev_get_drvdata(dev);
+	struct ti_queue_inst *qinst;
+	int i;
+
+	for (qinst = inst->qinsts, i = 0; i < inst->num_valid_queues; qinst++, i++) {
+		if (!qinst->is_tx)
+			ti_msgmgr_queue_rx_set_polled_mode(qinst, false);
+	}
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(ti_msgmgr_pm_ops, ti_msgmgr_suspend, ti_msgmgr_resume);
+
 /* Queue operations */
 static const struct mbox_chan_ops ti_msgmgr_chan_ops = {
 	.startup = ti_msgmgr_queue_startup,
@@ -839,6 +927,7 @@ static struct platform_driver ti_msgmgr_driver = {
 	.driver = {
 		   .name = "ti-msgmgr",
 		   .of_match_table = of_match_ptr(ti_msgmgr_of_match),
+		   .pm = &ti_msgmgr_pm_ops,
 	},
 };
 module_platform_driver(ti_msgmgr_driver);

include/linux/soc/ti/ti-msgmgr.h

@@ -1,7 +1,7 @@
 /*
  * Texas Instruments' Message Manager
  *
- * Copyright (C) 2015-2016 Texas Instruments Incorporated - https://www.ti.com/
+ * Copyright (C) 2015-2022 Texas Instruments Incorporated - https://www.ti.com/
  *	Nishanth Menon
  *
  * This program is free software; you can redistribute it and/or modify
@@ -17,10 +17,14 @@
 #ifndef TI_MSGMGR_H
 #define TI_MSGMGR_H
 
+struct mbox_chan;
+
 /**
  * struct ti_msgmgr_message - Message Manager structure
  * @len: Length of data in the Buffer
  * @buf: Buffer pointer
+ * @chan_rx: Expected channel for response, must be provided to use polled rx
+ * @timeout_rx_ms: Timeout value to use if polling for response
  *
  * This is the structure for data used in mbox_send_message
  * the length of data buffer used depends on the SoC integration
@@ -30,6 +34,8 @@
 struct ti_msgmgr_message {
 	size_t len;
 	u8 *buf;
+	struct mbox_chan *chan_rx;
+	int timeout_rx_ms;
 };
 
 #endif /* TI_MSGMGR_H */