[PATCH v6 1/2] dt-bindings: serial: sc16is7xx: Add description for polling mode

[PATCH v6 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
V6:
- 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 v6 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.
V6:
- Use polling mode for IRQ numbers <= 0 which encounter no valid IRQ
  were found/defined.
---
 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..560f45ed19ae 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 <= 0);
+	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 v6 2/2] serial: sc16is7xx: Add polling mode if no IRQ pin is available

[Andy Shevchenko]

On Mon, Jan 13, 2025 at 08:30:30AM +0100, Andre Werner wrote:
> 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.

pull ? Hmm...

...

> V6:
> - Use polling mode for IRQ numbers <= 0 which encounter no valid IRQ
>   were found/defined.

Thanks, this part looks better now.

...

> +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. */

Period.

> +	sc16is7xx_irq(0, s);
> +
> +	/* Setup delay based on SC16IS7XX_POLL_PERIOD_MS */

No period.

> +	kthread_queue_delayed_work(&s->kworker, &s->poll_work,
> +				   msecs_to_jiffies(SC16IS7XX_POLL_PERIOD_MS));
> +}

Please, go through the comments you added in the patch and use the style that
is mostly used in the driver for the similar (one-line comment) situations.

...

> +		/* Initialize kernel thread for polling */

Again, no period.

-- 
With Best Regards,
Andy Shevchenko

Re: [External Email] Re: [PATCH v6 2/2] serial: sc16is7xx: Add polling mode if no IRQ pin is available

[Andre Werner]

[-- Attachment #1: Type: text/plain, Size: 1768 bytes --]

On Mon, 13 Jan 2025, Andy Shevchenko wrote:

> On Mon, Jan 13, 2025 at 08:30:30AM +0100, Andre Werner wrote:
> > 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.
>
> pull ? Hmm...

Ah ... poll ... sorry.

>
> ...
>
> > V6:
> > - Use polling mode for IRQ numbers <= 0 which encounter no valid IRQ
> >   were found/defined.
>
> Thanks, this part looks better now.
>
> ...
>
> > +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. */
>
> Period.

What do you expect here? Shall I add the period time from the define as
the dedicated value? I do not understand what I should add here in
detail.

>
> > +	sc16is7xx_irq(0, s);
> > +
> > +	/* Setup delay based on SC16IS7XX_POLL_PERIOD_MS */
>
> No period.

Or do you mean that I add the define only once and not add all used
places?

>
> > +	kthread_queue_delayed_work(&s->kworker, &s->poll_work,
> > +				   msecs_to_jiffies(SC16IS7XX_POLL_PERIOD_MS));
> > +}
>
> Please, go through the comments you added in the patch and use the style that
> is mostly used in the driver for the similar (one-line comment) situations.
>
> ...
>
> > +		/* Initialize kernel thread for polling */
>
> Again, no period.

Same here. Do you expect the value here or the name of the used define?

>
> --
> With Best Regards,
> Andy Shevchenko
>
>
>

Thanks in advance

André

Re: [External Email] Re: [PATCH v6 2/2] serial: sc16is7xx: Add polling mode if no IRQ pin is available

[Andy Shevchenko]

On Mon, Jan 13, 2025 at 02:02:25PM +0100, Andre Werner wrote:
> On Mon, 13 Jan 2025, Andy Shevchenko wrote:
> > On Mon, Jan 13, 2025 at 08:30:30AM +0100, Andre Werner wrote:

...

> > > +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. */
> >
> > Period.
> 
> What do you expect here? Shall I add the period time from the define as
> the dedicated value? I do not understand what I should add here in
> detail.
> 
> >
> > > +	/* Setup delay based on SC16IS7XX_POLL_PERIOD_MS */
> >
> > No period.
> 
> Or do you mean that I add the define only once and not add all used
> places?

...

> > Please, go through the comments you added in the patch and use the style that
> > is mostly used in the driver for the similar (one-line comment) situations.

^^^ Read this. You have added three comments in two different styles.
It's not a big or anyhow critical issue in this case, it's matter of
the consistency with the existing style.

I expect that all three will in the same style, preferable the one
that is currently in use in the driver for other comments.

...

> > > +		/* Initialize kernel thread for polling */
> >
> > Again, no period.
> 
> Same here. Do you expect the value here or the name of the used define?


-- 
With Best Regards,
Andy Shevchenko