diff mbox series

[RFC] serial: sc16is7xx: fix broken port 0 uart init

Message ID 20230517194406.4125912-1-hugo@hugovil.com
State New
Headers
Series [RFC] serial: sc16is7xx: fix broken port 0 uart init |

Commit Message

Hugo Villeneuve May 17, 2023, 7:44 p.m. UTC 
  From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

While experimenting with rs485 configuration on a SC16IS752 dual UART,
I found that the sc16is7xx_config_rs485() function was called only for
the second port (index 1, channel B), causing initialization problems
for the first port.

For the sc16is7xx driver, port->membase and port->mapbase are not set,
and their default values are 0. And we set port->iobase to the device
index. This means that when the first device is registered using the
uart_add_one_port() function, the following values will be in the port
structure:
    port->membase = 0
    port->mapbase = 0
    port->iobase  = 0

Therefore, the function uart_configure_port() in serial_core.c will
exit early because of the following check:
	/*
	 * If there isn't a port here, don't do anything further.
	 */
	if (!port->iobase && !port->mapbase && !port->membase)
		return;

Typically, I2C and SPI drivers do not set port->membase and
port->mapbase. But I found that the max310x driver sets
port->membase to ~0 (all ones). By implementing the same change in our
driver, uart_configure_port() is now correctly executed.

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
---

I am not sure if this change is the best long-term solution to this
problem, and maybe uart_configure_port() itself could be modified to
take into account the fact that some devices have all three *base
values set to zero?

Also, many drivers use port->iobase as an index, is it the correct way
to use it?

For example, for our driver, there was
commit 5da6b1c079e6 ("sc16is7xx: Set iobase to device index") with the
following explanation:
    "Set the .iobase value to the relative index within the device to allow
    infering the order through sysfs."

 drivers/tty/serial/sc16is7xx.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Hugo Villeneuve May 25, 2023, 4:09 a.m. UTC | #1 
On Wed, 17 May 2023 15:44:07 -0400
Hugo Villeneuve <hugo@hugovil.com> wrote:

> From: Hugo Villeneuve <hvilleneuve@dimonoff.com>
> 
> While experimenting with rs485 configuration on a SC16IS752 dual UART,
> I found that the sc16is7xx_config_rs485() function was called only for
> the second port (index 1, channel B), causing initialization problems
> for the first port.
> 
> For the sc16is7xx driver, port->membase and port->mapbase are not set,
> and their default values are 0. And we set port->iobase to the device
> index. This means that when the first device is registered using the
> uart_add_one_port() function, the following values will be in the port
> structure:
>     port->membase = 0
>     port->mapbase = 0
>     port->iobase  = 0
> 
> Therefore, the function uart_configure_port() in serial_core.c will
> exit early because of the following check:
> 	/*
> 	 * If there isn't a port here, don't do anything further.
> 	 */
> 	if (!port->iobase && !port->mapbase && !port->membase)
> 		return;
> 
> Typically, I2C and SPI drivers do not set port->membase and
> port->mapbase. But I found that the max310x driver sets
> port->membase to ~0 (all ones). By implementing the same change in our
> driver, uart_configure_port() is now correctly executed.
> 
> Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
> ---
> 
> I am not sure if this change is the best long-term solution to this
> problem, and maybe uart_configure_port() itself could be modified to
> take into account the fact that some devices have all three *base
> values set to zero?
> 
> Also, many drivers use port->iobase as an index, is it the correct way
> to use it?
> 
> For example, for our driver, there was
> commit 5da6b1c079e6 ("sc16is7xx: Set iobase to device index") with the
> following explanation:
>     "Set the .iobase value to the relative index within the device to allow
>     infering the order through sysfs."
> 
>  drivers/tty/serial/sc16is7xx.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> index 1a3143331c1f..3e0e63498052 100644
> --- a/drivers/tty/serial/sc16is7xx.c
> +++ b/drivers/tty/serial/sc16is7xx.c
> @@ -1432,6 +1432,7 @@ static int sc16is7xx_probe(struct device *dev,
>  		s->p[i].port.fifosize	= SC16IS7XX_FIFO_SIZE;
>  		s->p[i].port.flags	= UPF_FIXED_TYPE | UPF_LOW_LATENCY;
>  		s->p[i].port.iobase	= i;
> +		s->p[i].port.membase	= (void __iomem *)~0;
>  		s->p[i].port.iotype	= UPIO_PORT;
>  		s->p[i].port.uartclk	= freq;
>  		s->p[i].port.rs485_config = sc16is7xx_config_rs485;
> -- 
> 2.30.2

This patch is now integrated in the following series:
https://lkml.org/lkml/2023/5/25/7
diff mbox series

Patch

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 1a3143331c1f..3e0e63498052 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -1432,6 +1432,7 @@  static int sc16is7xx_probe(struct device *dev,
 		s->p[i].port.fifosize	= SC16IS7XX_FIFO_SIZE;
 		s->p[i].port.flags	= UPF_FIXED_TYPE | UPF_LOW_LATENCY;
 		s->p[i].port.iobase	= i;
+		s->p[i].port.membase	= (void __iomem *)~0;
 		s->p[i].port.iotype	= UPIO_PORT;
 		s->p[i].port.uartclk	= freq;
 		s->p[i].port.rs485_config = sc16is7xx_config_rs485;