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Revert "serial: ns16550: fix debug uart putc called before init"

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This reverts commit 6f57c34473 since it
does not seem to work at least on rk3399.

The Rockchip Technical Reference Manual (TRM) for the rk3399 says the baud
rate prescaler register is readable only when USR[0] is zero. Since this
bit is defined as "reserved" in the socfpga cylcone5 TRM, let's rather
drop this than making the ns16550 debug uart more platform specific.

Reported-by: Roosen Henri <Henri.Roosen@ginzinger.com>
Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com
This commit is contained in:
Simon Goldschmidt 2018-12-03 21:55:33 +01:00 committed by Tom Rini
parent 7cfc1a381e
commit 1a67969a99
1 changed files with 2 additions and 16 deletions
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18
drivers/serial/ns16550.c
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@ -272,26 +272,12 @@ static inline void _debug_uart_init(void)
serial_dout(&com_port->lcr, UART_LCRVAL);
}
static inline int NS16550_read_baud_divisor(struct NS16550 *com_port)
{
int ret;
serial_dout(&com_port->lcr, UART_LCR_BKSE | UART_LCRVAL);
ret = serial_din(&com_port->dll) & 0xff;
ret |= (serial_din(&com_port->dlm) & 0xff) << 8;
serial_dout(&com_port->lcr, UART_LCRVAL);
return ret;
}
static inline void _debug_uart_putc(int ch)
{
struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE;
while (!(serial_din(&com_port->lsr) & UART_LSR_THRE)) {
if (!NS16550_read_baud_divisor(com_port))
return;
}
while (!(serial_din(&com_port->lsr) & UART_LSR_THRE))
;
serial_dout(&com_port->thr, ch);
}