serial: 8250_omap: Drop pm_runtime_irq_safe()

Let's drop the use of pm_runtime_irq_safe() for 8250_omap. The use of
pm_runtime_irq_safe() is not nice as it takes a permanent usage count on
the parent device.

We can finally drop pm_runtime_irq_safe() safely as the kernel now knows
when the uart port tx is active. This changed with commit 84a9582fd203
("serial: core: Start managing serial controllers to enable runtime PM").

For serial port rx, we already use Linux generic wakeirqs for 8250_omap.

To drop pm_runtime_irq_safe(), we need to add handling for shallow idle
state where the port hardware may already be awake and an IO interrupt
happens. We also need to replace the serial8250_rpm sync calls in the
interrupt handlers with async runtime PM calls.

Note that omap8250_irq() calls omap_8250_dma_handle_irq(), so we don't
need separate runtime PM calls in omap_8250_dma_handle_irq().

While at it, let's also add the missing line break to the end of
omap8250_runtime_resume() to group the calls.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20231004062650.64487-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 9ea38e2a6e23cb21529d0c9cbb454de21c956676..1192207d23210e402d3fe8772137a6ad17ee11b2 100644 (file)
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -8,6 +8,7 @@
  *
  */
 
+#include <linux/atomic.h>
 #include <linux/clk.h>
 #include <linux/device.h>
 #include <linux/io.h>
@@ -130,6 +131,7 @@ struct omap8250_priv {
 
        u8 tx_trigger;
        u8 rx_trigger;
+       atomic_t active;
        bool is_suspending;
        int wakeirq;
        int wakeups_enabled;
@@ -632,14 +634,23 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
        unsigned int iir, lsr;
        int ret;
 
+       pm_runtime_get_noresume(port->dev);
+
+       /* Shallow idle state wake-up to an IO interrupt? */
+       if (atomic_add_unless(&priv->active, 1, 1)) {
+               priv->latency = priv->calc_latency;
+               schedule_work(&priv->qos_work);
+       }
+
 #ifdef CONFIG_SERIAL_8250_DMA
        if (up->dma) {
                ret = omap_8250_dma_handle_irq(port);
+               pm_runtime_mark_last_busy(port->dev);
+               pm_runtime_put(port->dev);
                return IRQ_RETVAL(ret);
        }
 #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);
@@ -676,7 +687,8 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
                schedule_delayed_work(&up->overrun_backoff, delay);
        }
 
-       serial8250_rpm_put(up);
+       pm_runtime_mark_last_busy(port->dev);
+       pm_runtime_put(port->dev);
 
        return IRQ_RETVAL(ret);
 }
@@ -1270,11 +1282,8 @@ static int omap_8250_dma_handle_irq(struct uart_port *port)
        u16 status;
        u8 iir;
 
-       serial8250_rpm_get(up);
-
        iir = serial_port_in(port, UART_IIR);
        if (iir & UART_IIR_NO_INT) {
-               serial8250_rpm_put(up);
                return IRQ_HANDLED;
        }
 
@@ -1305,7 +1314,6 @@ static int omap_8250_dma_handle_irq(struct uart_port *port)
 
        uart_unlock_and_check_sysrq(port);
 
-       serial8250_rpm_put(up);
        return 1;
 }
 
@@ -1503,8 +1511,6 @@ 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);
@@ -1748,6 +1754,7 @@ static int omap8250_runtime_suspend(struct device *dev)
 
        priv->latency = PM_QOS_CPU_LATENCY_DEFAULT_VALUE;
        schedule_work(&priv->qos_work);
+       atomic_set(&priv->active, 0);
 
        return 0;
 }
@@ -1757,6 +1764,10 @@ static int omap8250_runtime_resume(struct device *dev)
        struct omap8250_priv *priv = dev_get_drvdata(dev);
        struct uart_8250_port *up = NULL;
 
+       /* Did the hardware wake to a device IO interrupt before a wakeirq? */
+       if (atomic_read(&priv->active))
+               return 0;
+
        if (priv->line >= 0)
                up = serial8250_get_port(priv->line);
 
@@ -1772,8 +1783,10 @@ static int omap8250_runtime_resume(struct device *dev)
                uart_port_unlock_irq(&up->port);
        }
 
+       atomic_set(&priv->active, 1);
        priv->latency = priv->calc_latency;
        schedule_work(&priv->qos_work);
+
        return 0;
 }