Re: [PATCH v11 5/5] drivers/tty/serial: add LiteUART driver

[Mateusz Holenko <mholenko@antmicro.com>]

Hi Geert,

On Fri, Sep 25, 2020 at 3:41 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Mateusz,
>
> On Wed, Sep 23, 2020 at 12:12 PM Mateusz Holenko <mholenko@antmicro.com> wrote:
> > From: Filip Kokosinski <fkokosinski@antmicro.com>
> >
> > This commit adds driver for the FPGA-based LiteUART serial controller
> > from LiteX SoC builder.
> >
> > The current implementation supports LiteUART configured
> > for 32 bit data width and 8 bit CSR bus width.
> >
> > It does not support IRQ.
> >
> > Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>
> > Signed-off-by: Mateusz Holenko <mholenko@antmicro.com>
>
> Thanks for your patch!

Thanks for your review!

>
> > --- /dev/null
> > +++ b/drivers/tty/serial/liteuart.c
>
> > +static int liteuart_probe(struct platform_device *pdev)
> > +{
> > +       struct device_node *np = pdev->dev.of_node;
> > +       struct liteuart_port *uart;
> > +       struct uart_port *port;
> > +       struct xa_limit limit;
> > +       int dev_id, ret;
> > +
> > +       /* no device tree */
> > +       if (!np)
> > +               return -ENODEV;
> > +
> > +       /* look for aliases; auto-enumerate for free index if not found */
> > +       dev_id = of_alias_get_id(np, "serial");
> > +       if (dev_id < 0)
> > +               limit = XA_LIMIT(0, CONFIG_SERIAL_LITEUART_MAX_PORTS);
> > +       else
> > +               limit = XA_LIMIT(dev_id, dev_id);
> > +
> > +       uart = kzalloc(sizeof(struct liteuart_port), GFP_KERNEL);
>
> Who frees this memory? Use devm_kzalloc()?

You are right - it leaks right now. We'll switch to devm_kzalloc().

> > +       if (!uart)
> > +               return -ENOMEM;
> > +
> > +       ret = xa_alloc(&liteuart_array, &dev_id, uart, limit, GFP_KERNEL);
>
> Who frees this entry?

We'll add a call to xa_erase() when removing the driver.

> > +       if (ret)
> > +               return ret;
> > +
> > +       port = &uart->port;
> > +
> > +       /* get membase */
> > +       port->membase = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
> > +       if (!port->membase)
> > +               return -ENXIO;
> > +
> > +       /* values not from device tree */
> > +       port->dev = &pdev->dev;
> > +       port->iotype = UPIO_MEM;
> > +       port->flags = UPF_BOOT_AUTOCONF;
> > +       port->ops = &liteuart_ops;
> > +       port->regshift = 2;
> > +       port->fifosize = 16;
> > +       port->iobase = 1;
> > +       port->type = PORT_UNKNOWN;
> > +       port->line = dev_id;
> > +       spin_lock_init(&port->lock);
> > +
> > +       return uart_add_one_port(&liteuart_driver, &uart->port);
> > +}
>
> > +static int __init liteuart_init(void)
> > +{
> > +       int res;
> > +
> > +       res = uart_register_driver(&liteuart_driver);
> > +       if (res)
> > +               return res;
> > +
> > +       res = platform_driver_register(&liteuart_platform_driver);
> > +       if (res) {
> > +               uart_unregister_driver(&liteuart_driver);
> > +               return res;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static void __exit liteuart_exit(void)
> > +{
> > +       platform_driver_unregister(&liteuart_platform_driver);
> > +       uart_unregister_driver(&liteuart_driver);
> > +}
> > +
> > +module_init(liteuart_init);
> > +module_exit(liteuart_exit);
>
> Several drivers call uart_{,un}register_driver() from their .probe()
> resp. .remove() callbacks, so they can use module_platform_driver()
> instead of the above boilerplate.  Greg, what's your stance on that?

I don't have much experience here and can't tell which version is the
preferred one.

> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds

Best regards,
Mateusz

--
Mateusz Holenko
Antmicro Ltd | www.antmicro.com
Roosevelta 22, 60-829 Poznan, Poland