On 01/11/2016 11:06 AM, Peter Hurley wrote:
> On 01/11/2016 09:56 AM, Sebastian Frias wrote:
>> On 01/11/2016 05:11 PM, Peter Hurley wrote:
>>> On 01/11/2016 07:07 AM, Sebastian Frias wrote:
>>>> On 12/22/2015 06:56 PM, Sebastian Frias wrote:
[...]
>> 2) What would it take to make the "rt2880" work with the 8250
>> earlycon? I mean, it is already pretty much supported in there, what
>> would be missing? (I don't see why it blocks on earlycon_map) And
>> would it be worth doing?
>
> The rt2880 does not have the same register locations as a 8250.
> The 8250 port driver remaps all register accesses with a LUT.
>
> Adding support would be trivial.
Please test.
--- >% ---
Subject: [PATCH] serial: 8250: Add Au1x00/RT288x earlycon support
Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_early.c | 52 ++++++++++++++++++++++++++++++++++++
include/uapi/linux/serial_reg.h | 13 +++++++++
2 files changed, 65 insertions(+)
diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index af62131..307fb23 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -145,3 +145,55 @@ EARLYCON_DECLARE(uart8250, early_serial8250_setup);
EARLYCON_DECLARE(uart, early_serial8250_setup);
OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
+
+
+#ifdef CONFIG_SERIAL_8250_RT288X
+
+static void __init rt288x_putc(struct uart_port *port, int c)
+{
+ unsigned int status;
+
+ serial8250_early_out(port, AU1x00_TX, c);
+
+ for (;;) {
+ status = serial8250_early_in(port, AU1x00_LSR);
+ if ((status & BOTH_EMPTY) == BOTH_EMPTY)
+ break;
+ cpu_relax();
+ }
+}
+
+static void __init early_rt288x_write(struct console *console,
+ const char *s, unsigned int count)
+{
+ struct earlycon_device *device = console->data;
+ struct uart_port *port = &device->port;
+
+ uart_console_write(port, s, count, rt288x_putc);
+}
+
+static int __init early_rt288x_setup(struct earlycon_device *device,
+ const char *options)
+{
+ struct uart_port *port = &device->port;
+ unsigned int ier;
+
+ if (!(device->port.membase || device->port.iobase))
+ return -ENODEV;
+
+ /* Don't support direct init or any line-setting options */
+ if (device->baud)
+ return -EINVAL;
+
+ /* assume the device was initialized, only mask interrupts */
+ ier = serial8250_early_in(port, AU1x00_IER);
+ serial8250_early_out(port, AU1x00_IER, ier);
+
+ device->con->write = early_rt288x_write;
+ return 0;
+}
+
+EARLYCON_DECLARE(rt288x, early_rt288x_setup);
+OF_EARLYCON_DECLARE(rt288x, "ralink,rt2880-uart", early_rt288x_setup);
+
+#endif /* CONFIG_SERIAL_8250_RT288X */
diff --git a/include/uapi/linux/serial_reg.h b/include/uapi/linux/serial_reg.h
index 1e5ac4e7..4d068ac 100644
--- a/include/uapi/linux/serial_reg.h
+++ b/include/uapi/linux/serial_reg.h
@@ -376,5 +376,18 @@
#define UART_EXAR_TXTRG 0x0a /* Tx FIFO trigger level write-only */
#define UART_EXAR_RXTRG 0x0b /* Rx FIFO trigger level write-only */
+/*
+ * Register offsets for Au1x00/RT288x 8250-workalikes
+ */
+#define AU1x00_RX 0
+#define AU1x00_TX 1
+#define AU1x00_IER 2
+#define AU1x00_IIR 3
+#define AU1x00_FCR 4
+#define AU1x00_LCR 5
+#define AU1x00_MCR 6
+#define AU1x00_LSR 7
+#define AU1x00_MSR 8
+
#endif /* _LINUX_SERIAL_REG_H */
--
2.7.0
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