disable FB

hc

2024-01-04 1543e317f1da31b75942316931e8f491a8920811

 kernel/drivers/tty/serial/8250/8250_early.c
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@@ -109,6 +109,28 @@
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 	uart_console_write(port, s, count, serial_putc);
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 }
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+#ifdef CONFIG_CONSOLE_POLL
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+static int early_serial8250_read(struct console *console,
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+				 char *s, unsigned int count)
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+{
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+	struct earlycon_device *device = console->data;
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+	struct uart_port *port = &device->port;
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+	unsigned int status;
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+	int num_read = 0;
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+
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+	while (num_read < count) {
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+		status = serial8250_early_in(port, UART_LSR);
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+		if (!(status & UART_LSR_DR))
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+			break;
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+		s[num_read++] = serial8250_early_in(port, UART_RX);
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+	}
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+
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+	return num_read;
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+}
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+#else
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+#define early_serial8250_read NULL
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+#endif
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+
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 static void __init init_port(struct earlycon_device *device)
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 {
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 	struct uart_port *port = &device->port;
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@@ -149,6 +171,7 @@
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 		init_port(device);
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 	device->con->write = early_serial8250_write;
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+	device->con->read = early_serial8250_read;
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 	return 0;
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 }
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 EARLYCON_DECLARE(uart8250, early_serial8250_setup);