2023-08-02 15:42:00

by Jisheng Zhang

Subject: [PATCH 0/2] serial: 8250_dw: fall back to poll if there's no interrupt

When there's no irq(this can be due to various reasons, for example,
no irq from HW support, or we just want to use poll solution, and so
on), falling back to poll is still better than no support at all.

patch1 makes the interrupt property in dt-binding optional
patch2 falls back to poll if there's no interrupt

Jisheng Zhang (2):
dt-bindings: serial: snps-dw-apb-uart: make interrupt optional
serial: 8250_dw: fall back to poll if there's no interrupt

.../devicetree/bindings/serial/snps-dw-apb-uart.yaml | 1 -
drivers/tty/serial/8250/8250_dw.c | 8 ++++++--
2 files changed, 6 insertions(+), 3 deletions(-)

--
2.40.1

2023-08-02 15:44:22

by Jisheng Zhang

Subject: [PATCH 2/2] serial: 8250_dw: fall back to poll if there's no interrupt

When there's no irq(this can be due to various reasons, for example,
no irq from HW support, or we just want to use poll solution, and so
on), falling back to poll is still better than no support at all.

Signed-off-by: Jisheng Zhang <[email protected]>
---
drivers/tty/serial/8250/8250_dw.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 7db51781289e..39db768517eb 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -524,8 +524,12 @@ static int dw8250_probe(struct platform_device *pdev)
return dev_err_probe(dev, -EINVAL, "no registers defined\n");

irq = platform_get_irq(pdev, 0);
- if (irq < 0)
- return irq;
+ if (irq < 0) {
+ if (irq != -ENXIO)
+ return irq;
+ /* no interrupt -> fall back to polling */
+ irq = 0;
+ }

spin_lock_init(&p->lock);
p->mapbase = regs->start;
--
2.40.1

2023-08-02 16:53:02

by Jisheng Zhang

Subject: [PATCH 1/2] dt-bindings: serial: snps-dw-apb-uart: make interrupt optional

The driver fall back to poll style when there's no irq. "poll" still
looks better than no support.

Signed-off-by: Jisheng Zhang <[email protected]>
---
Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml | 1 -
1 file changed, 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
index 3862411c77b5..17c553123f96 100644
--- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
+++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
@@ -117,7 +117,6 @@ properties:
required:
- compatible
- reg
- - interrupts

unevaluatedProperties: false

--
2.40.1

2023-08-02 23:16:35

by Andy Shevchenko

Subject: Re: [PATCH 2/2] serial: 8250_dw: fall back to poll if there's no interrupt

On Wed, Aug 02, 2023 at 11:05:45PM +0800, Jisheng Zhang wrote:
> When there's no irq(this can be due to various reasons, for example,
> no irq from HW support, or we just want to use poll solution, and so
> on), falling back to poll is still better than no support at all.

...

> irq = platform_get_irq(pdev, 0);

You will still have an error message. Perhaps you need to replace it with

irq = platform_get_irq_optional(pdev, 0);

> - if (irq < 0)
> - return irq;
> + if (irq < 0) {
> + if (irq != -ENXIO)
> + return irq;
> + /* no interrupt -> fall back to polling */
> + irq = 0;
> + }

This can be slightly modified:

/* no interrupt -> fall back to polling */
if (irq == -ENXIO)
irq = 0;
if (irq < 0)
return irq;

--
With Best Regards,
Andy Shevchenko