From 39f809192661be91fabc3ee77c2e15f9123c11cf Mon Sep 17 00:00:00 2001 From: Lanqing Liu Date: Thu, 19 Sep 2019 11:10:37 +0800 Subject: [PATCH] serial: sprd: Add polling IO support In order to access the UART without the interrupts, the kernel uses the basic polling methods for IO with the device. With these methods implemented, it is now possible to enable kgdb during early boot over serial. Signed-off-by: Lanqing Liu Reviewed-by: Baolin Wang Tested-by: Baolin Wang Link: https://lore.kernel.org/r/f112a741c053ac5fb0637e2f058be81e17f78ccc.1568862391.git.liuhhome@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/sprd_serial.c | 33 ++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c index 771d111965231..31df235025623 100644 --- a/drivers/tty/serial/sprd_serial.c +++ b/drivers/tty/serial/sprd_serial.c @@ -919,6 +919,34 @@ static void sprd_pm(struct uart_port *port, unsigned int state, } } +#ifdef CONFIG_CONSOLE_POLL +static int sprd_poll_init(struct uart_port *port) +{ + if (port->state->pm_state != UART_PM_STATE_ON) { + sprd_pm(port, UART_PM_STATE_ON, 0); + port->state->pm_state = UART_PM_STATE_ON; + } + + return 0; +} + +static int sprd_poll_get_char(struct uart_port *port) +{ + while (!(serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK)) + cpu_relax(); + + return serial_in(port, SPRD_RXD); +} + +static void sprd_poll_put_char(struct uart_port *port, unsigned char ch) +{ + while (serial_in(port, SPRD_STS1) & SPRD_TX_FIFO_CNT_MASK) + cpu_relax(); + + serial_out(port, SPRD_TXD, ch); +} +#endif + static const struct uart_ops serial_sprd_ops = { .tx_empty = sprd_tx_empty, .get_mctrl = sprd_get_mctrl, @@ -936,6 +964,11 @@ static const struct uart_ops serial_sprd_ops = { .config_port = sprd_config_port, .verify_port = sprd_verify_port, .pm = sprd_pm, +#ifdef CONFIG_CONSOLE_POLL + .poll_init = sprd_poll_init, + .poll_get_char = sprd_poll_get_char, + .poll_put_char = sprd_poll_put_char, +#endif }; #ifdef CONFIG_SERIAL_SPRD_CONSOLE -- 2.30.2