Re: [RFC PATCH] always probe UART HW when options are not specified
From: Peter Hurley <hidden>
Date: 2016-01-11 19:57:47
Also in:
lkml
Subsystem:
8250/16?50 (and clone uarts) serial driver, the rest, tty layer and serial drivers · Maintainers:
Greg Kroah-Hartman, Linus Torvalds, Jiri Slaby
Possibly related (same subject, not in this thread)
- 2015-12-17 · Re: [RFC PATCH] always probe UART HW when options are not specified · Måns Rullgård <hidden>
On 01/11/2016 11:06 AM, Peter Hurley wrote:
On 01/11/2016 09:56 AM, Sebastian Frias wrote:quoted
On 01/11/2016 05:11 PM, Peter Hurley wrote:quoted
On 01/11/2016 07:07 AM, Sebastian Frias wrote:quoted
On 12/22/2015 06:56 PM, Sebastian Frias wrote:
[...]
quoted
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 <redacted> --- 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 */
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2.7.0