On Wed, 17 May 2023 15:44:07 -0400
Hugo Villeneuve <hugo@xxxxxxxxxxx> wrote:
> From: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxx>
> ---
>
> 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
