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UPSTREAM: serial: sprd: Add polling IO support

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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.

bug: 146864653
Signed-off-by: Lanqing Liu <liuhhome@gmail.com>
Reviewed-by: Baolin Wang <baolin.wang@linaro.org>
Tested-by: Baolin Wang <baolin.wang@linaro.org>
Link: https://lore.kernel.org/r/f112a741c053ac5fb0637e2f058be81e17f78ccc.1568862391.git.liuhhome@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 39f809192661be91fabc3ee77c2e15f9123c11cf)
This commit is contained in:
Lanqing Liu 2019-09-19 11:10:37 +08:00 • committed by Greg Kroah-Hartman
commit 862815883c
1 changed files with 33 additions and 0 deletions
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33
drivers/tty/serial/sprd_serial.c
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@ -922,6 +922,34 @@ 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,
@ -939,6 +967,11 @@ 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