Hi Claudiu,
On Wed, Dec 4, 2024 at 4:58 PM Claudiu <claudiu.beznea@xxxxxxxxx> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
>
> In the sh-sci driver, sci_ports[0] is used by earlycon. If the earlycon is
> still active when sci_probe() is called and the new serial port is supposed
> to map to sci_ports[0], return -EBUSY to prevent breaking the earlycon.
>
> This situation should occurs in debug scenarios, and users should be
> aware of the potential conflict.
>
> Fixes: 0b0cced19ab1 ("serial: sh-sci: Add CONFIG_SERIAL_EARLYCON support")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
Thanks for your patch!
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -158,6 +158,7 @@ struct sci_port {
> bool has_rtscts;
> bool autorts;
> bool tx_occurred;
> + bool earlycon;
This is only used in sci_ports[0], so it can be a single global flag,
instead of a flag embedded in each sci_port structure.
> };
>
> #define SCI_NPORTS CONFIG_SERIAL_SH_SCI_NR_UARTS
> @@ -3443,6 +3444,7 @@ static int sci_probe_single(struct platform_device *dev,
> static int sci_probe(struct platform_device *dev)
> {
> struct plat_sci_port *p;
> + struct resource *res;
> struct sci_port *sp;
> unsigned int dev_id;
> int ret;
> @@ -3472,6 +3474,26 @@ static int sci_probe(struct platform_device *dev)
> }
>
> sp = &sci_ports[dev_id];
> +
> + /*
> + * In case:
> + * - the probed port alias is zero (as the one used by earlycon), and
> + * - the earlycon is still active (e.g., "earlycon keep_bootcon" in
> + * bootargs)
This is even true without "keep_bootcon", as nothing ever clears the
sci_port.earlycon flag once it is set.
> + *
> + * defer the probe of this serial. This is a debug scenario and the user
> + * must be aware of it.
> + *
> + * Except when the probed port is the same as the earlycon port.
> + */
> +
> + res = platform_get_resource(dev, IORESOURCE_MEM, 0);
> + if (!res)
> + return -ENODEV;
> +
> + if (sp->earlycon && res->start != sp->port.mapbase)
> + return dev_err_probe(&dev->dev, -EBUSY, "sci_port[0] is used by earlycon!\n");
> +
> platform_set_drvdata(dev, sp);
>
> ret = sci_probe_single(dev, dev_id, p, sp);
> @@ -3568,6 +3590,7 @@ static int __init early_console_setup(struct earlycon_device *device,
> port_cfg.type = type;
> sci_ports[0].cfg = &port_cfg;
> sci_ports[0].params = sci_probe_regmap(&port_cfg);
> + sci_ports[0].earlycon = true;
> port_cfg.scscr = sci_serial_in(&sci_ports[0].port, SCSCR);
> sci_serial_out(&sci_ports[0].port, SCSCR,
> SCSCR_RE | SCSCR_TE | port_cfg.scscr);
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
