serial: 8250_early: Support kgdboc_earlycon (c5e7467d) · Commits · 戴 / test

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@chromium.org> Reviewed-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by:

Daniel Thompson <daniel.thompson@linaro.org> Link: https://lore.kernel.org/r/20200507130644.v4.11.I8f668556c244776523320a95b09373a86eda11b7@changeid Signed-off-by:

Daniel Thompson <daniel.thompson@linaro.org>

drivers/tty/serial/8250/8250_early.c

+23 −0

Original line number	Diff line number	Diff line
		@@ -109,6 +109,28 @@ static void early_serial8250_write(struct console *console,
		uart_console_write(port, s, count, serial_putc);
		}

		#ifdef CONFIG_CONSOLE_POLL
		static int early_serial8250_read(struct console *console,
		char *s, unsigned int count)
		{
		struct earlycon_device *device = console->data;
		struct uart_port *port = &device->port;
		unsigned int status;
		int num_read = 0;

		while (num_read < count) {
		status = serial8250_early_in(port, UART_LSR);
		if (!(status & UART_LSR_DR))
		break;
		s[num_read++] = serial8250_early_in(port, UART_RX);
		}

		return num_read;
		}
		#else
		#define early_serial8250_read NULL
		#endif

		static void __init init_port(struct earlycon_device *device)
		{
		struct uart_port *port = &device->port;
		@@ -149,6 +171,7 @@ int __init early_serial8250_setup(struct earlycon_device *device,
		init_port(device);

		device->con->write = early_serial8250_write;
		device->con->read = early_serial8250_read;
		return 0;
		}
		EARLYCON_DECLARE(uart8250, early_serial8250_setup);

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