serial: sccnxp: Implement polling mode

This patch adds support for polling work mode, i.e. system is perform
periodical check chip status when IRQ-line is not connected to CPU.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 103 insertions, 45 deletions

diff --git a/drivers/tty/serial/sccnxp.c b/drivers/tty/serial/sccnxp.c
index 2ced871becff..3a4c57e6ea1e 100644
--- a/drivers/tty/serial/sccnxp.c
+++ b/drivers/tty/serial/sccnxp.c
@@ -23,6 +23,7 @@
 #include <linux/io.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
+#include <linux/spinlock.h>
 #include <linux/platform_device.h>
 #include <linux/platform_data/sccnxp.h>
 
@@ -106,6 +107,7 @@ enum {
 struct sccnxp_port {
         struct uart_driver      uart;
         struct uart_port        port[SCCNXP_MAX_UARTS];
+        bool                    opened[SCCNXP_MAX_UARTS];
 
         const char              *name;
         int                     irq;
@@ -122,7 +124,10 @@ struct sccnxp_port {
         struct console          console;
 #endif
 
-        struct mutex            sccnxp_mutex;
+        spinlock_t              lock;
+
+        bool                    poll;
+        struct timer_list       timer;
 
         struct sccnxp_pdata     pdata;
 };
@@ -371,31 +376,48 @@ static void sccnxp_handle_tx(struct uart_port *port)
                 uart_write_wakeup(port);
 }
 
-static irqreturn_t sccnxp_ist(int irq, void *dev_id)
+static void sccnxp_handle_events(struct sccnxp_port *s)
 {
         int i;
         u8 isr;
-        struct sccnxp_port *s = (struct sccnxp_port *)dev_id;
-
-        mutex_lock(&s->sccnxp_mutex);
 
-        for (;;) {
+        do {
                 isr = sccnxp_read(&s->port[0], SCCNXP_ISR_REG);
                 isr &= s->imr;
                 if (!isr)
                         break;
 
-                dev_dbg(s->port[0].dev, "IRQ status: 0x%02x\n", isr);
-
                 for (i = 0; i < s->uart.nr; i++) {
-                        if (isr & ISR_RXRDY(i))
+                        if (s->opened[i] && (isr & ISR_RXRDY(i)))
                                 sccnxp_handle_rx(&s->port[i]);
-                        if (isr & ISR_TXRDY(i))
+                        if (s->opened[i] && (isr & ISR_TXRDY(i)))
                                 sccnxp_handle_tx(&s->port[i]);
                 }
-        }
+        } while (1);
+}
+
+static void sccnxp_timer(unsigned long data)
+{
+        struct sccnxp_port *s = (struct sccnxp_port *)data;
+        unsigned long flags;
 
-        mutex_unlock(&s->sccnxp_mutex);
+        spin_lock_irqsave(&s->lock, flags);
+        sccnxp_handle_events(s);
+        spin_unlock_irqrestore(&s->lock, flags);
+
+        if (!timer_pending(&s->timer))
+                mod_timer(&s->timer, jiffies +
+                          usecs_to_jiffies(s->pdata.poll_time_us));
+}
+
+static irqreturn_t sccnxp_ist(int irq, void *dev_id)
+{
+        struct sccnxp_port *s = (struct sccnxp_port *)dev_id;
+        unsigned long flags;
+
+        spin_lock_irqsave(&s->lock, flags);
+        sccnxp_handle_events(s);
+        spin_unlock_irqrestore(&s->lock, flags);
 
         return IRQ_HANDLED;
 }
@@ -403,8 +425,9 @@ static irqreturn_t sccnxp_ist(int irq, void *dev_id)
 static void sccnxp_start_tx(struct uart_port *port)
 {
         struct sccnxp_port *s = dev_get_drvdata(port->dev);
+        unsigned long flags;
 
-        mutex_lock(&s->sccnxp_mutex);
+        spin_lock_irqsave(&s->lock, flags);
 
         /* Set direction to output */
         if (s->flags & SCCNXP_HAVE_IO)
@@ -412,7 +435,7 @@ static void sccnxp_start_tx(struct uart_port *port)
 
         sccnxp_enable_irq(port, IMR_TXRDY);
 
-        mutex_unlock(&s->sccnxp_mutex);
+        spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static void sccnxp_stop_tx(struct uart_port *port)
@@ -423,20 +446,22 @@ static void sccnxp_stop_tx(struct uart_port *port)
 static void sccnxp_stop_rx(struct uart_port *port)
 {
         struct sccnxp_port *s = dev_get_drvdata(port->dev);
+        unsigned long flags;
 
-        mutex_lock(&s->sccnxp_mutex);
+        spin_lock_irqsave(&s->lock, flags);
         sccnxp_port_write(port, SCCNXP_CR_REG, CR_RX_DISABLE);
-        mutex_unlock(&s->sccnxp_mutex);
+        spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static unsigned int sccnxp_tx_empty(struct uart_port *port)
 {
         u8 val;
+        unsigned long flags;
         struct sccnxp_port *s = dev_get_drvdata(port->dev);
 
-        mutex_lock(&s->sccnxp_mutex);
+        spin_lock_irqsave(&s->lock, flags);
         val = sccnxp_port_read(port, SCCNXP_SR_REG);
-        mutex_unlock(&s->sccnxp_mutex);
+        spin_unlock_irqrestore(&s->lock, flags);
 
         return (val & SR_TXEMT) ? TIOCSER_TEMT : 0;
 }
@@ -449,28 +474,30 @@ static void sccnxp_enable_ms(struct uart_port *port)
 static void sccnxp_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
         struct sccnxp_port *s = dev_get_drvdata(port->dev);
+        unsigned long flags;
 
         if (!(s->flags & SCCNXP_HAVE_IO))
                 return;
 
-        mutex_lock(&s->sccnxp_mutex);
+        spin_lock_irqsave(&s->lock, flags);
 
         sccnxp_set_bit(port, DTR_OP, mctrl & TIOCM_DTR);
         sccnxp_set_bit(port, RTS_OP, mctrl & TIOCM_RTS);
 
-        mutex_unlock(&s->sccnxp_mutex);
+        spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static unsigned int sccnxp_get_mctrl(struct uart_port *port)
 {
         u8 bitmask, ipr;
+        unsigned long flags;
         struct sccnxp_port *s = dev_get_drvdata(port->dev);
         unsigned int mctrl = TIOCM_DSR | TIOCM_CTS | TIOCM_CAR;
 
         if (!(s->flags & SCCNXP_HAVE_IO))
                 return mctrl;
 
-        mutex_lock(&s->sccnxp_mutex);
+        spin_lock_irqsave(&s->lock, flags);
 
         ipr = ~sccnxp_read(port, SCCNXP_IPCR_REG);
 
@@ -499,7 +526,7 @@ static unsigned int sccnxp_get_mctrl(struct uart_port *port)
                 mctrl |= (ipr & bitmask) ? TIOCM_RNG : 0;
         }
 
-        mutex_unlock(&s->sccnxp_mutex);
+        spin_unlock_irqrestore(&s->lock, flags);
 
         return mctrl;
 }
@@ -507,21 +534,23 @@ static unsigned int sccnxp_get_mctrl(struct uart_port *port)
 static void sccnxp_break_ctl(struct uart_port *port, int break_state)
 {
         struct sccnxp_port *s = dev_get_drvdata(port->dev);
+        unsigned long flags;
 
-        mutex_lock(&s->sccnxp_mutex);
+        spin_lock_irqsave(&s->lock, flags);
         sccnxp_port_write(port, SCCNXP_CR_REG, break_state ?
                           CR_CMD_START_BREAK : CR_CMD_STOP_BREAK);
-        mutex_unlock(&s->sccnxp_mutex);
+        spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static void sccnxp_set_termios(struct uart_port *port,
                                struct ktermios *termios, struct ktermios *old)
 {
         struct sccnxp_port *s = dev_get_drvdata(port->dev);
+        unsigned long flags;
         u8 mr1, mr2;
         int baud;
 
-        mutex_lock(&s->sccnxp_mutex);
+        spin_lock_irqsave(&s->lock, flags);
 
         /* Mask termios capabilities we don't support */
         termios->c_cflag &= ~CMSPAR;
@@ -588,20 +617,22 @@ static void sccnxp_set_termios(struct uart_port *port,
         /* Update timeout according to new baud rate */
         uart_update_timeout(port, termios->c_cflag, baud);
 
+        /* Report actual baudrate back to core */
         if (tty_termios_baud_rate(termios))
                 tty_termios_encode_baud_rate(termios, baud, baud);
 
         /* Enable RX & TX */
         sccnxp_port_write(port, SCCNXP_CR_REG, CR_RX_ENABLE | CR_TX_ENABLE);
 
-        mutex_unlock(&s->sccnxp_mutex);
+        spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static int sccnxp_startup(struct uart_port *port)
 {
         struct sccnxp_port *s = dev_get_drvdata(port->dev);
+        unsigned long flags;
 
-        mutex_lock(&s->sccnxp_mutex);
+        spin_lock_irqsave(&s->lock, flags);
 
         if (s->flags & SCCNXP_HAVE_IO) {
                 /* Outputs are controlled manually */
@@ -620,7 +651,9 @@ static int sccnxp_startup(struct uart_port *port)
         /* Enable RX interrupt */
         sccnxp_enable_irq(port, IMR_RXRDY);
 
-        mutex_unlock(&s->sccnxp_mutex);
+        s->opened[port->line] = 1;
+
+        spin_unlock_irqrestore(&s->lock, flags);
 
         return 0;
 }
@@ -628,8 +661,11 @@ static int sccnxp_startup(struct uart_port *port)
 static void sccnxp_shutdown(struct uart_port *port)
 {
         struct sccnxp_port *s = dev_get_drvdata(port->dev);
+        unsigned long flags;
+
+        spin_lock_irqsave(&s->lock, flags);
 
-        mutex_lock(&s->sccnxp_mutex);
+        s->opened[port->line] = 0;
 
         /* Disable interrupts */
         sccnxp_disable_irq(port, IMR_TXRDY | IMR_RXRDY);
@@ -641,7 +677,7 @@ static void sccnxp_shutdown(struct uart_port *port)
         if (s->flags & SCCNXP_HAVE_IO)
                 sccnxp_set_bit(port, DIR_OP, 0);
 
-        mutex_unlock(&s->sccnxp_mutex);
+        spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static const char *sccnxp_type(struct uart_port *port)
@@ -715,10 +751,11 @@ static void sccnxp_console_write(struct console *co, const char *c, unsigned n)
 {
         struct sccnxp_port *s = (struct sccnxp_port *)co->data;
         struct uart_port *port = &s->port[co->index];
+        unsigned long flags;
 
-        mutex_lock(&s->sccnxp_mutex);
+        spin_lock_irqsave(&s->lock, flags);
         uart_console_write(port, c, n, sccnxp_console_putchar);
-        mutex_unlock(&s->sccnxp_mutex);
+        spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static int sccnxp_console_setup(struct console *co, char *options)
@@ -757,7 +794,7 @@ static int sccnxp_probe(struct platform_device *pdev)
         }
         platform_set_drvdata(pdev, s);
 
-        mutex_init(&s->sccnxp_mutex);
+        spin_lock_init(&s->lock);
 
         /* Individual chip settings */
         switch (chiptype) {
@@ -854,11 +891,19 @@ static int sccnxp_probe(struct platform_device *pdev)
         } else
                 memcpy(&s->pdata, pdata, sizeof(struct sccnxp_pdata));
 
-        s->irq = platform_get_irq(pdev, 0);
-        if (s->irq <= 0) {
-                dev_err(&pdev->dev, "Missing irq resource data\n");
-                ret = -ENXIO;
-                goto err_out;
+        if (pdata->poll_time_us) {
+                dev_info(&pdev->dev, "Using poll mode, resolution %u usecs\n",
+                         pdata->poll_time_us);
+                s->poll = 1;
+        }
+
+        if (!s->poll) {
+                s->irq = platform_get_irq(pdev, 0);
+                if (s->irq < 0) {
+                        dev_err(&pdev->dev, "Missing irq resource data\n");
+                        ret = -ENXIO;
+                        goto err_out;
+                }
         }
 
         /* Check input frequency */
@@ -923,13 +968,23 @@ static int sccnxp_probe(struct platform_device *pdev)
         if (s->pdata.init)
                 s->pdata.init();
 
-        ret = devm_request_threaded_irq(&pdev->dev, s->irq, NULL, sccnxp_ist,
-                                        IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
-                                        dev_name(&pdev->dev), s);
-        if (!ret)
+        if (!s->poll) {
+                ret = devm_request_threaded_irq(&pdev->dev, s->irq, NULL,
+                                                sccnxp_ist,
+                                                IRQF_TRIGGER_FALLING |
+                                                IRQF_ONESHOT,
+                                                dev_name(&pdev->dev), s);
+                if (!ret)
+                        return 0;
+
+                dev_err(&pdev->dev, "Unable to reguest IRQ %i\n", s->irq);
+        } else {
+                init_timer(&s->timer);
+                setup_timer(&s->timer, sccnxp_timer, (unsigned long)s);
+                mod_timer(&s->timer, jiffies +
+                          usecs_to_jiffies(s->pdata.poll_time_us));
                 return 0;
-
-        dev_err(&pdev->dev, "Unable to reguest IRQ %i\n", s->irq);
+        }
 
 err_out:
         platform_set_drvdata(pdev, NULL);
@@ -942,7 +997,10 @@ static int sccnxp_remove(struct platform_device *pdev)
         int i;
         struct sccnxp_port *s = platform_get_drvdata(pdev);
 
-        devm_free_irq(&pdev->dev, s->irq, s);
+        if (!s->poll)
+                devm_free_irq(&pdev->dev, s->irq, s);
+        else
+                del_timer_sync(&s->timer);
 
         for (i = 0; i < s->uart.nr; i++)
                 uart_remove_one_port(&s->uart, &s->port[i]);