On Thu, 25 May 2023 14:20:59 +0300 (EEST)
Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> wrote:
> On Thu, 25 May 2023, Hugo Villeneuve wrote:
>
> > From: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
> >
> > While experimenting with rs485 configuration on a SC16IS752 dual UART,
>
> You can remove this intro, it's not necessary.
Fixed.
> > 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.
>
> Just start with:
>
> sc16is7xx_config_rs485() function is called only for ...
>
> > 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).
>
> The max310x driver sets port->membase to ~0 (all ones) to solve the same
> problem.
Fixed.
> > By implementing the same change in our
> > driver, uart_configure_port() is now correctly executed.
>
> our driver -> this driver
Fixed.
> This changelog was really well describing the problem! :-)
>
> > Fixes: dfeae619d781 ("serial: sc16is7xx")
> > 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?
>
> Yeah, some other solution should be devised. Maybe we should add another
> .iotype for thse kind of devices. But I'm fine with this for this fix.
> After editing the changelog, feel free to add:
>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Added.
> > Also, many drivers use port->iobase as an index, is it the correct way
> > to use it?
>
> "Many" for this and max310x? Besides that, uartlite.c has a comment which
> says "mark port in use".
Ok,
anyway with your approval I will remove these comments which will not part of the final commit message anyway.
Hugo.
> > 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 af7e66db54b4..8a2fc6f89d36 100644
> > --- a/drivers/tty/serial/sc16is7xx.c
> > +++ b/drivers/tty/serial/sc16is7xx.c
> > @@ -1443,6 +1443,7 @@ 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;
> >
