linux-kernel - [PATCH 6/6] serial: 8250_omap: Drop the use of pm_runtime_irq

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Date:   Tue, 21 Sep 2021 13:33:46 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...el.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Johan Hovold <johan@...nel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-serial@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 6/6] serial: 8250_omap: Drop the use of pm_runtime_irq_safe()

We already have the serial layer RX wake path fixed for power management.
We no longer allow deeper idle states unless the kernel console has been
detached, and we require that the RX wakeirq is configured.

For TX path, we may have the serial port autoidled, and need to wake it
up before writing to it. With the serial_core prep_tx() changes, we can
finally drop the dependency to pm_runtime_irq_safe() for 8250_omap driver.

To drop pm_runtime_irq_safe(), we remove all PM runtime calls from the
interrupt context. If we ever see an interrupt for an idled port, we just
bail out. We now also need to restore the port context with interrupts
disabled to prevent interrupts from happening while restoring the port.

Signed-off-by: Tony Lindgren <tony@...mide.com>
---
 drivers/tty/serial/8250/8250_omap.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -134,6 +134,7 @@ struct omap8250_priv {
 	bool rx_dma_broken;
 	bool throttled;
 	unsigned int allow_rpm:1;
+	unsigned int clocks_off:1;
 };
 
 struct omap8250_dma_params {
@@ -621,6 +622,9 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
 	unsigned int iir, lsr;
 	int ret;
 
+	if (priv->clocks_off)
+		return IRQ_NONE;
+
 #ifdef CONFIG_SERIAL_8250_DMA
 	if (up->dma) {
 		ret = omap_8250_dma_handle_irq(port);
@@ -628,7 +632,6 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
 	}
 #endif
 
-	serial8250_rpm_get(up);
 	lsr = serial_port_in(port, UART_LSR);
 	iir = serial_port_in(port, UART_IIR);
 	ret = serial8250_handle_irq(port, iir);
@@ -662,8 +665,6 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
 		schedule_delayed_work(&up->overrun_backoff, delay);
 	}
 
-	serial8250_rpm_put(up);
-
 	return IRQ_RETVAL(ret);
 }
 
@@ -1191,13 +1192,9 @@ static int omap_8250_dma_handle_irq(struct uart_port *port)
 	unsigned char status;
 	u8 iir;
 
-	serial8250_rpm_get(up);
-
 	iir = serial_port_in(port, UART_IIR);
-	if (iir & UART_IIR_NO_INT) {
-		serial8250_rpm_put(up);
+	if (iir & UART_IIR_NO_INT)
 		return IRQ_HANDLED;
-	}
 
 	spin_lock(&port->lock);
 
@@ -1226,7 +1223,6 @@ static int omap_8250_dma_handle_irq(struct uart_port *port)
 
 	uart_unlock_and_check_sysrq(port);
 
-	serial8250_rpm_put(up);
 	return 1;
 }
 
@@ -1420,8 +1416,6 @@ static int omap8250_probe(struct platform_device *pdev)
 	if (!of_get_available_child_count(pdev->dev.of_node))
 		pm_runtime_set_autosuspend_delay(&pdev->dev, -1);
 
-	pm_runtime_irq_safe(&pdev->dev);
-
 	pm_runtime_get_sync(&pdev->dev);
 
 	omap_serial_fill_features_erratas(&up, priv);
@@ -1637,6 +1631,8 @@ static int omap8250_runtime_suspend(struct device *dev)
 		omap_8250_rx_dma_flush(up);
 
 	priv->latency = PM_QOS_CPU_LATENCY_DEFAULT_VALUE;
+	priv->clocks_off = 1;
+
 	schedule_work(&priv->qos_work);
 
 	return 0;
@@ -1646,13 +1642,18 @@ static int omap8250_runtime_resume(struct device *dev)
 {
 	struct omap8250_priv *priv = dev_get_drvdata(dev);
 	struct uart_8250_port *up;
+	struct uart_port *port;
+	unsigned long flags;
 
 	/* In case runtime-pm tries this before we are setup */
 	if (!priv)
 		return 0;
 
 	up = serial8250_get_port(priv->line);
+	port = &up->port;
 
+	/* Restore state with interrupts disabled */
+	spin_lock_irqsave(&port->lock, flags);
 	if (omap8250_lost_context(up))
 		omap8250_restore_regs(up);
 
@@ -1660,6 +1661,9 @@ static int omap8250_runtime_resume(struct device *dev)
 		omap_8250_rx_dma(up);
 
 	priv->latency = priv->calc_latency;
+	priv->clocks_off = 0;
+	spin_unlock_irqrestore(&port->lock, flags);
+
 	schedule_work(&priv->qos_work);
 	return 0;
 }
-- 
2.33.0