[PATCH v5 1/2] dt-bindings: serial: sc16is7xx: Add description for polling mode

[PATCH v5 1/2] dt-bindings: serial: sc16is7xx: Add description for polling mode

[Andre Werner]

Polling mode is enabled if the "interrupts" property is missing.
Thus, this commit deletes "interrupts" entry from "required" section
and adds a description for the fallback to polling mode at the
"interrupts" entry.

Signed-off-by: Andre Werner <andre.werner@systec-electronic.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
---
V3:
- No changes on source.
- Add Acked-By to commit message.
V4:
- No changes
V5:
- No changes
---
 Documentation/devicetree/bindings/serial/nxp,sc16is7xx.yaml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/serial/nxp,sc16is7xx.yaml b/Documentation/devicetree/bindings/serial/nxp,sc16is7xx.yaml
index 88871480018e..ab39b95dae40 100644
--- a/Documentation/devicetree/bindings/serial/nxp,sc16is7xx.yaml
+++ b/Documentation/devicetree/bindings/serial/nxp,sc16is7xx.yaml
@@ -23,6 +23,8 @@ properties:
     maxItems: 1
 
   interrupts:
+    description:
+      When missing, device driver uses polling instead.
     maxItems: 1
 
   clocks:
@@ -76,7 +78,6 @@ properties:
 required:
   - compatible
   - reg
-  - interrupts
 
 allOf:
   - $ref: /schemas/spi/spi-peripheral-props.yaml#
-- 
2.47.1

[PATCH v5 2/2] serial: sc16is7xx: Add polling mode if no IRQ pin is available

[Andre Werner]

Fall back to polling mode if no interrupt is configured because there
is no possibility to connect the interrupt pin.
If "interrupts" property is missing in devicetree the driver
uses a delayed worker to pull the state of interrupt status registers.

Signed-off-by: Andre Werner <andre.werner@systec-electronic.com>
---
V2:
- Change warning for polling mode to debug log entry
- Correct typo: Resuse -> Reuse
- Format define with missing tabs for SC16IS7XX_POLL_PERIOD
- Format struct declaration sc16is7xx_one_config with missing tabs for polling and shutdown
- Adapt dtbinding with new polling feature
V3:
- Use suffix with units and drop a comment SC16IS7XX_POLL_PERIOD_MS. Sorry for that miss.
- Make Kernel lowercase.
V4:
- Reword commit messages for better understanding.
- Remove 'shutdown' property for canceling delayed worker.
- Rename worker function: sc16is7xx_transmission_poll -> sc16is7xx_poll_proc
- Unify argument for worker functions: kthread_work *work -> kthread_work *ws
V5:
- Replace of_property check with IRQ number check to set polling
  property. This will add support for usage without device tree
  definitions. Thanks for that advice.
- Add blank line es requested.
---
 drivers/tty/serial/sc16is7xx.c | 37 ++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index a3093e09309f..7b51cdc274fd 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -314,6 +314,7 @@
 #define SC16IS7XX_FIFO_SIZE		(64)
 #define SC16IS7XX_GPIOS_PER_BANK	4
 
+#define SC16IS7XX_POLL_PERIOD_MS	10
 #define SC16IS7XX_RECONF_MD		BIT(0)
 #define SC16IS7XX_RECONF_IER		BIT(1)
 #define SC16IS7XX_RECONF_RS485		BIT(2)
@@ -348,6 +349,8 @@ struct sc16is7xx_port {
 	u8				mctrl_mask;
 	struct kthread_worker		kworker;
 	struct task_struct		*kworker_task;
+	struct kthread_delayed_work	poll_work;
+	bool				polling;
 	struct sc16is7xx_one		p[];
 };
 
@@ -861,6 +864,18 @@ static irqreturn_t sc16is7xx_irq(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static void sc16is7xx_poll_proc(struct kthread_work *ws)
+{
+	struct sc16is7xx_port *s = container_of(ws, struct sc16is7xx_port, poll_work.work);
+
+	/* Reuse standard IRQ handler. Interrupt ID is unused in this context. */
+	sc16is7xx_irq(0, s);
+
+	/* Setup delay based on SC16IS7XX_POLL_PERIOD_MS */
+	kthread_queue_delayed_work(&s->kworker, &s->poll_work,
+				   msecs_to_jiffies(SC16IS7XX_POLL_PERIOD_MS));
+}
+
 static void sc16is7xx_tx_proc(struct kthread_work *ws)
 {
 	struct uart_port *port = &(to_sc16is7xx_one(ws, tx_work)->port);
@@ -1149,6 +1164,7 @@ static int sc16is7xx_config_rs485(struct uart_port *port, struct ktermios *termi
 static int sc16is7xx_startup(struct uart_port *port)
 {
 	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
+	struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
 	unsigned int val;
 	unsigned long flags;
 
@@ -1211,6 +1227,10 @@ static int sc16is7xx_startup(struct uart_port *port)
 	sc16is7xx_enable_ms(port);
 	uart_port_unlock_irqrestore(port, flags);
 
+	if (s->polling)
+		kthread_queue_delayed_work(&s->kworker, &s->poll_work,
+					   msecs_to_jiffies(SC16IS7XX_POLL_PERIOD_MS));
+
 	return 0;
 }
 
@@ -1232,6 +1252,9 @@ static void sc16is7xx_shutdown(struct uart_port *port)
 
 	sc16is7xx_power(port, 0);
 
+	if (s->polling)
+		kthread_cancel_delayed_work_sync(&s->poll_work);
+
 	kthread_flush_worker(&s->kworker);
 }
 
@@ -1538,6 +1561,11 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
 	/* Always ask for fixed clock rate from a property. */
 	device_property_read_u32(dev, "clock-frequency", &uartclk);
 
+	s->polling = !!irq;
+	if (s->polling)
+		dev_dbg(dev,
+			"No interrupt pin definition, falling back to polling mode\n");
+
 	s->clk = devm_clk_get_optional(dev, NULL);
 	if (IS_ERR(s->clk))
 		return PTR_ERR(s->clk);
@@ -1665,6 +1693,12 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
 		goto out_ports;
 #endif
 
+	if (s->polling) {
+		/* Initialize kernel thread for polling */
+		kthread_init_delayed_work(&s->poll_work, sc16is7xx_poll_proc);
+		return 0;
+	}
+
 	/*
 	 * Setup interrupt. We first try to acquire the IRQ line as level IRQ.
 	 * If that succeeds, we can allow sharing the interrupt as well.
@@ -1724,6 +1758,9 @@ void sc16is7xx_remove(struct device *dev)
 		sc16is7xx_power(&s->p[i].port, 0);
 	}
 
+	if (s->polling)
+		kthread_cancel_delayed_work_sync(&s->poll_work);
+
 	kthread_flush_worker(&s->kworker);
 	kthread_stop(s->kworker_task);
 
-- 
2.47.1

Re: [PATCH v5 2/2] serial: sc16is7xx: Add polling mode if no IRQ pin is available

[Hugo Villeneuve]

On Fri, 10 Jan 2025 20:37:29 +0200
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> пʼятниця, 10 січня 2025 р. Andre Werner <andre.werner@systec-electronic.com>
> пише:
> 
> > Fall back to polling mode if no interrupt is configured because there
> > is no possibility to connect the interrupt pin.
> > If "interrupts" property is missing in devicetree the driver
> > uses a delayed worker to pull the state of interrupt status registers.
> >
> > Signed-off-by: Andre Werner <andre.werner@systec-electronic.com>
> > ---
> > V2:
> > - Change warning for polling mode to debug log entry
> > - Correct typo: Resuse -> Reuse
> > - Format define with missing tabs for SC16IS7XX_POLL_PERIOD
> > - Format struct declaration sc16is7xx_one_config with missing tabs for
> > polling and shutdown
> > - Adapt dtbinding with new polling feature
> > V3:
> > - Use suffix with units and drop a comment SC16IS7XX_POLL_PERIOD_MS. Sorry
> > for that miss.
> > - Make Kernel lowercase.
> > V4:
> > - Reword commit messages for better understanding.
> > - Remove 'shutdown' property for canceling delayed worker.
> > - Rename worker function: sc16is7xx_transmission_poll ->
> > sc16is7xx_poll_proc
> > - Unify argument for worker functions: kthread_work *work -> kthread_work
> > *ws
> > V5:
> > - Replace of_property check with IRQ number check to set polling
> >   property. This will add support
> 
> 
> >
> It other way around, i.e. it won’t break the existing support of
> interrupt-driven non-DT setups.
> 
> 
> > for usage without device tree
> >   definitions. Thanks for that advice.
> > - Add blank line es requested.
> > ---
> >  drivers/tty/serial/sc16is7xx.c | 37 ++++++++++++++++++++++++++++++++++
> >  1 file changed, 37 insertions(+)
> >
> > diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/
> > sc16is7xx.c
> > index a3093e09309f..7b51cdc274fd 100644
> > --- a/drivers/tty/serial/sc16is7xx.c
> > +++ b/drivers/tty/serial/sc16is7xx.c
> > @@ -314,6 +314,7 @@
> >  #define SC16IS7XX_FIFO_SIZE            (64)
> >  #define SC16IS7XX_GPIOS_PER_BANK       4
> >
> > +#define SC16IS7XX_POLL_PERIOD_MS       10
> >  #define SC16IS7XX_RECONF_MD            BIT(0)
> >  #define SC16IS7XX_RECONF_IER           BIT(1)
> >  #define SC16IS7XX_RECONF_RS485         BIT(2)
> > @@ -348,6 +349,8 @@ struct sc16is7xx_port {
> >         u8                              mctrl_mask;
> >         struct kthread_worker           kworker;
> >         struct task_struct              *kworker_task;
> > +       struct kthread_delayed_work     poll_work;
> > +       bool                            polling;
> >         struct sc16is7xx_one            p[];
> >  };
> >
> > @@ -861,6 +864,18 @@ static irqreturn_t sc16is7xx_irq(int irq, void
> > *dev_id)
> >         return IRQ_HANDLED;
> >  }
> >
> > +static void sc16is7xx_poll_proc(struct kthread_work *ws)
> > +{
> > +       struct sc16is7xx_port *s = container_of(ws, struct sc16is7xx_port,
> > poll_work.work);
> > +
> > +       /* Reuse standard IRQ handler. Interrupt ID is unused in this
> > context. */
> > +       sc16is7xx_irq(0, s);
> > +
> > +       /* Setup delay based on SC16IS7XX_POLL_PERIOD_MS */
> > +       kthread_queue_delayed_work(&s->kworker, &s->poll_work,
> > +                                  msecs_to_jiffies(SC16IS7XX_
> > POLL_PERIOD_MS));
> > +}
> > +
> >  static void sc16is7xx_tx_proc(struct kthread_work *ws)
> >  {
> >         struct uart_port *port = &(to_sc16is7xx_one(ws, tx_work)->port);
> > @@ -1149,6 +1164,7 @@ static int sc16is7xx_config_rs485(struct uart_port
> > *port, struct ktermios *termi
> >  static int sc16is7xx_startup(struct uart_port *port)
> >  {
> >         struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
> > +       struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
> >         unsigned int val;
> >         unsigned long flags;
> >
> > @@ -1211,6 +1227,10 @@ static int sc16is7xx_startup(struct uart_port *port)
> >         sc16is7xx_enable_ms(port);
> >         uart_port_unlock_irqrestore(port, flags);
> >
> > +       if (s->polling)
> > +               kthread_queue_delayed_work(&s->kworker, &s->poll_work,
> > +                                          msecs_to_jiffies(SC16IS7XX_
> > POLL_PERIOD_MS));
> > +
> >         return 0;
> >  }
> >
> > @@ -1232,6 +1252,9 @@ static void sc16is7xx_shutdown(struct uart_port
> > *port)
> >
> >         sc16is7xx_power(port, 0);
> >
> > +       if (s->polling)
> > +               kthread_cancel_delayed_work_sync(&s->poll_work);
> > +
> >         kthread_flush_worker(&s->kworker);
> >  }
> >
> > @@ -1538,6 +1561,11 @@ int sc16is7xx_probe(struct device *dev, const
> > struct sc16is7xx_devtype *devtype,
> >         /* Always ask for fixed clock rate from a property. */
> >         device_property_read_u32(dev, "clock-frequency", &uartclk);
> >
> > +       s->polling = !!irq;
> 
> 
> This is incorrect, you should check for positive numbers only for IRQ
> support and for the rest otherwise. I do not see that frameworks guarantee
> this never be negative.

Hi Greg,
I just noticed that v5 of this patch is now in the tty-testing
branch. It should not, as there is currently a v6 fixing it, and
possibly a v7 coming.

Hugo.



> > +       if (s->polling)
> > +               dev_dbg(dev,
> > +                       "No interrupt pin definition, falling back to
> > polling mode\n");
> > +
> >         s->clk = devm_clk_get_optional(dev, NULL);
> >         if (IS_ERR(s->clk))
> >                 return PTR_ERR(s->clk);
> > @@ -1665,6 +1693,12 @@ int sc16is7xx_probe(struct device *dev, const
> > struct sc16is7xx_devtype *devtype,
> >                 goto out_ports;
> >  #endif
> >
> > +       if (s->polling) {
> > +               /* Initialize kernel thread for polling */
> > +               kthread_init_delayed_work(&s->poll_work,
> > sc16is7xx_poll_proc);
> > +               return 0;
> 
> 
> 
> > +       }
> > +
> >         /*
> >          * Setup interrupt. We first try to acquire the IRQ line as level
> > IRQ.
> >          * If that succeeds, we can allow sharing the interrupt as well.
> > @@ -1724,6 +1758,9 @@ void sc16is7xx_remove(struct device *dev)
> >                 sc16is7xx_power(&s->p[i].port, 0);
> >         }
> >
> > +       if (s->polling)
> > +               kthread_cancel_delayed_work_sync(&s->poll_work);
> > +
> >         kthread_flush_worker(&s->kworker);
> >         kthread_stop(s->kworker_task);
> >
> > --
> > 2.47.1
> >
> >


-- 
Hugo Villeneuve