[PATCH v2] serial: meson: add Magic SysRq support
From: Yixun Lan <hidden>
Date: 2017-09-06 13:53:20
Also in:
linux-amlogic, linux-serial, lkml
Subsystem:
the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
This dirver try to implement the Magic SysRq support[1] for Amlogic Inc's meson platfo
From the hardware perspective, the UART IP can't detect the 'BREAK' command
clearly via the status register. Instead, we rely on the combination of 'FRAME_ERR bit && ch == 0', and it works fine. [1] Documentation/admin-guide/sysrq.rst Signed-off-by: Yixun Lan <redacted> --- Changes since v1 at [0]: - add changelog & a few more comments [0] https://patchwork.kernel.org/patch/9728475/ --- drivers/tty/serial/meson_uart.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 42e4a4c7597f..3fea24bafd80 100644
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c@@ -14,6 +14,10 @@ * */ +#if defined(CONFIG_SERIAL_MESON_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ) +#define SUPPORT_SYSRQ +#endif + #include <linux/clk.h> #include <linux/console.h> #include <linux/delay.h>
@@ -183,12 +187,12 @@ static void meson_receive_chars(struct uart_port *port) { struct tty_port *tport = &port->state->port; char flag; - u32 status, ch, mode; + u32 ostatus, status, ch, mode; do { flag = TTY_NORMAL; port->icount.rx++; - status = readl(port->membase + AML_UART_STATUS); + ostatus = status = readl(port->membase + AML_UART_STATUS); if (status & AML_UART_ERR) { if (status & AML_UART_TX_FIFO_WERR)
@@ -216,6 +220,16 @@ static void meson_receive_chars(struct uart_port *port) ch = readl(port->membase + AML_UART_RFIFO); ch &= 0xff; + if ((ostatus & AML_UART_FRAME_ERR) && (ch == 0)) { + port->icount.brk++; + flag = TTY_BREAK; + if (uart_handle_break(port)) + continue; + } + + if (uart_handle_sysrq_char(port, ch)) + continue; + if ((status & port->ignore_status_mask) == 0) tty_insert_flip_char(tport, ch, flag);
--
2.14.1