Re: [PATCH] serial/liteuart; Add support for earlycon
From: Jiri Slaby <jirislaby@kernel.org>
Date: 2021-05-17 08:18:52
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On 15. 05. 21, 10:45, Stafford Horne wrote:
quoted hunk ↗ jump to hunk
Most litex boards using RISC-V soft cores us the sbi earlycon, however this is not available for non RISC-V litex SoC. This patch enables earlycon for liteuart which is available on all Litex SoC's making support for earycon debugging more widely available. Signed-off-by: Stafford Horne <shorne@gmail.com> Cc: Florent Kermarrec <redacted> Cc: Mateusz Holenko <mholenko@antmicro.com> Cc: Joel Stanley <joel@jms.id.au> Cc: Gabriel L. Somlo <gsomlo@gmail.com> --- .../admin-guide/kernel-parameters.txt | 5 +++ drivers/tty/serial/Kconfig | 1 + drivers/tty/serial/liteuart.c | 31 +++++++++++++++++++ 3 files changed, 37 insertions(+)diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 04545725f187..2d4a43af8de2 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt@@ -1084,6 +1084,11 @@ the driver will use only 32-bit accessors to read/write the device registers. + liteuart,<addr> + Start an early console on a litex serial port at the + specified address. The serial port must already be + setup and configured. Options are not yet supported. + meson,<addr> Start an early, polled-mode console on a meson serial port at the specified address. The serial port mustdiff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig index 0c4cd4a348f4..9ceffe6ab6fd 100644 --- a/drivers/tty/serial/Kconfig +++ b/drivers/tty/serial/Kconfig@@ -1531,6 +1531,7 @@ config SERIAL_LITEUART depends on OF || COMPILE_TEST depends on LITEX select SERIAL_CORE + select SERIAL_EARLYCON help This driver is for the FPGA-based LiteUART serial controller from LiteX SoC builder.diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c index 64842f3539e1..38c472487e68 100644 --- a/drivers/tty/serial/liteuart.c +++ b/drivers/tty/serial/liteuart.c@@ -372,6 +372,37 @@ static int __init liteuart_console_init(void) console_initcall(liteuart_console_init); #endif /* CONFIG_SERIAL_LITEUART_CONSOLE */ +#ifdef CONFIG_SERIAL_EARLYCON +static void early_liteuart_putc(struct uart_port *port, int c) +{ + while (litex_read8(port->membase + OFF_TXFULL)) + cpu_relax(); + + litex_write8(port->membase + OFF_RXTX, c);
Hi, am I missing something or this doesn't differ to liteuart_putchar?
+}
+
+static void early_liteuart_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, early_liteuart_putc);
+}
+
+static int __init early_liteuart_setup(struct earlycon_device *device,
+ const char *options)
+{
+ if (!device->port.membase)
+ return -ENODEV;
+
+ device->con->write = early_liteuart_write;
+ return 0;
+}
+
+OF_EARLYCON_DECLARE(liteuart, "litex,liteuart", early_liteuart_setup);
+#endif /* CONFIG_SERIAL_EARLYCON */
+
static int __init liteuart_init(void)
{
int res;-- js suse labs