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Message-ID: <CAMuHMdXz8FHRLPOuHPKvjmq2FCidY20MrCmSsq+pK1QUg-fk2A@mail.gmail.com>
Date: Thu, 19 Dec 2024 15:26:14 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Claudiu <claudiu.beznea@...on.dev>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org,
wsa+renesas@...g-engineering.com, prabhakar.mahadev-lad.rj@...renesas.com,
lethal@...ux-sh.org, g.liakhovetski@....de, groeck@...omium.org,
mka@...omium.org, ulrich.hecht+renesas@...il.com, ysato@...rs.sourceforge.jp,
linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
linux-renesas-soc@...r.kernel.org,
Claudiu Beznea <claudiu.beznea.uj@...renesas.com>, stable@...r.kernel.org
Subject: Re: [PATCH RFT 5/6] serial: sh-sci: Clean sci_ports[0] after at
earlycon exit
Hi Claudiu,
On Wed, Dec 4, 2024 at 4:58 PM Claudiu <claudiu.beznea@...on.dev> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>
> The early_console_setup() function initializes sci_ports[0].port with an
> object of type struct uart_port obtained from the struct earlycon_device
> passed as an argument to early_console_setup().
>
> Later, during serial port probing, the serial port used as earlycon
> (e.g., port A) might be remapped to a different position in the sci_ports[]
> array, and a different serial port (e.g., port B) might be assigned to slot
> 0. For example:
>
> sci_ports[0] = port B
> sci_ports[X] = port A
>
> In this scenario, the new port mapped at index zero (port B) retains the
> data associated with the earlycon configuration. Consequently, after the
> Linux boot process, any access to the serial port now mapped to
> sci_ports[0] (port B) will block the original earlycon port (port A).
>
> To address this, introduce an early_console_exit() function to clean up
> sci_ports[0] when earlycon is exited.
>
> To prevent the cleanup of sci_ports[0] while the serial device is still
> being used by earlycon, introduce the struct sci_port::probing flag and
> account for it in early_console_exit().
>
> Fixes: 0b0cced19ab1 ("serial: sh-sci: Add CONFIG_SERIAL_EARLYCON support")
> Cc: stable@...r.kernel.org
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> ---
>
> Changes since the integrated patch:
> - adjust the commit message to address Geert comments at [1]
> - Introduce the struct sci_port::probing flag to prevent the cleanup
> of sci_ports[0] while the serial device is still being used by earlycon
Thanks for the update!
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -159,6 +159,7 @@ struct sci_port {
> bool autorts;
> bool tx_occurred;
> bool earlycon;
> + bool probing;
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
> @@ -3386,7 +3387,8 @@ static struct plat_sci_port *sci_parse_dt(struct platform_device *pdev,
> static int sci_probe_single(struct platform_device *dev,
> unsigned int index,
> struct plat_sci_port *p,
> - struct sci_port *sciport)
> + struct sci_port *sciport,
> + struct resource *sci_res)
> {
> int ret;
>
> @@ -3433,12 +3435,15 @@ static int sci_probe_single(struct platform_device *dev,
> sciport->port.flags |= UPF_HARD_FLOW;
> }
>
> - ret = uart_add_one_port(&sci_uart_driver, &sciport->port);
> - if (ret) {
> - return ret;
> + if (sci_ports[0].earlycon && sci_ports[0].port.mapbase == sci_res->start) {
> + /*
> + * Skip cleanup up the sci_port[0] in early_console_exit(), this
Double up
> + * port is the same as the earlycon one.
> + */
> + sci_ports[0].probing = true;
> }
>
> - return 0;
> + return uart_add_one_port(&sci_uart_driver, &sciport->port);
> }
>
> static int sci_probe(struct platform_device *dev)
> @@ -3496,7 +3501,7 @@ static int sci_probe(struct platform_device *dev)
>
> platform_set_drvdata(dev, sp);
>
> - ret = sci_probe_single(dev, dev_id, p, sp);
> + ret = sci_probe_single(dev, dev_id, p, sp, res);
> if (ret)
> return ret;
>
> @@ -3579,6 +3584,20 @@ sh_early_platform_init_buffer("earlyprintk", &sci_driver,
> #ifdef CONFIG_SERIAL_SH_SCI_EARLYCON
> static struct plat_sci_port port_cfg;
>
> +static int early_console_exit(struct console *co)
> +{
> + struct sci_port *sci_port = &sci_ports[0];
> +
> + /*
> + * Clean the slot used by earlycon. A new SCI device might
> + * map to this slot.
> + */
> + if (sci_port->earlycon && !sci_port->probing)
> + memset(sci_port, 0, sizeof(*sci_port));
Aha, so this clears sci_port.earlycon, too (cfr. my comment on
PATCH 4/6). Still, I don't think this is sufficient: shouldn't
sci_port.earlycon be cleared unconditionally?
> +
> + return 0;
> +}
> +
> static int __init early_console_setup(struct earlycon_device *device,
> int type)
> {
> @@ -3596,6 +3615,8 @@ static int __init early_console_setup(struct earlycon_device *device,
> SCSCR_RE | SCSCR_TE | port_cfg.scscr);
>
> device->con->write = serial_console_write;
> + device->con->exit = early_console_exit;
> +
> return 0;
> }
> static int __init sci_early_console_setup(struct earlycon_device *device,
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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
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