linux-kernel - Re: [PATCH v2 8/9] serial: qcom_geni_serial: Support earlycon

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Date:   Mon, 27 Apr 2020 17:48:16 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     jason.wessel@...driver.com, gregkh@...uxfoundation.org,
        kgdb-bugreport@...ts.sourceforge.net, mingo@...hat.com,
        hpa@...or.com, bp@...en8.de, linux-serial@...r.kernel.org,
        agross@...nel.org, tglx@...utronix.de, frowand.list@...il.com,
        bjorn.andersson@...aro.org, jslaby@...e.com,
        catalin.marinas@....com, corbet@....net, will@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 8/9] serial: qcom_geni_serial: Support earlycon_kgdboc

On Tue, Apr 21, 2020 at 02:14:46PM -0700, Douglas Anderson wrote:
> Implement the read() function in the early console driver.  With
> recent kgdb patches this allows you to use kgdb to debug fairly early
> into the system boot.
> 
> We only bother implementing this if polling is enabled since kgdb
> can't be enabled without that.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> 
> Changes in v2: None
> 
>  drivers/tty/serial/qcom_geni_serial.c | 32 +++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index 6119090ce045..4563d152b39e 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -1090,6 +1090,36 @@ static void qcom_geni_serial_earlycon_write(struct console *con,
>  	__qcom_geni_serial_console_write(&dev->port, s, n);
>  }
>  
> +#ifdef CONFIG_CONSOLE_POLL
> +static int qcom_geni_serial_earlycon_read(struct console *con,
> +					  char *s, unsigned int n)
> +{
> +	struct earlycon_device *dev = con->data;
> +	struct uart_port *uport = &dev->port;
> +	int num_read = 0;
> +	int ch;
> +
> +	while (num_read < n) {
> +		ch = qcom_geni_serial_get_char(uport);
> +		if (ch == NO_POLL_CHAR)
> +			break;
> +		s[num_read++] = ch;
> +	}
> +
> +	return num_read;
> +}
> +
> +static void __init qcom_geni_serial_enable_early_read(struct geni_se *se,
> +						      struct console *con)
> +{
> +	geni_se_setup_s_cmd(se, UART_START_READ, 0);
> +	con->read = qcom_geni_serial_earlycon_read;
> +}
> +#else
> +static inline void qcom_geni_serial_enable_early_read(struct geni_se *se,
> +						      struct console *con) { ; }

This is pure nitpicking but since I was passing... why the ; ?


Daniel.