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driver: serial: fixed the buffer underflow issue when clearing the port.

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Set DLAB bit before reading RDR to avoid buffer underflow.

Signed-off-by: Peng Li <lipengit@gmail.com>
This commit is contained in:
Peng Li 2021-04-12 21:11:22 -07:00 • committed by Ioannis Glaropoulos
commit e28b7e04e2
1 changed files with 4 additions and 1 deletions
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5
drivers/serial/uart_ns16550.c
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@ -339,7 +339,7 @@ static int uart_ns16550_configure(const struct device *dev,
{ {
struct uart_ns16550_dev_data_t * const dev_data = DEV_DATA(dev); struct uart_ns16550_dev_data_t * const dev_data = DEV_DATA(dev);
const struct uart_ns16550_device_config * const dev_cfg = DEV_CFG(dev); const struct uart_ns16550_device_config * const dev_cfg = DEV_CFG(dev);
uint8_t lcr_cache;
uint8_t mdc = 0U; uint8_t mdc = 0U;
/* temp for return value if error occurs in this locked region */ /* temp for return value if error occurs in this locked region */
@ -466,7 +466,10 @@ static int uart_ns16550_configure(const struct device *dev,
); );
/* clear the port */ /* clear the port */
lcr_cache = INBYTE(LCR(dev));
OUTBYTE(LCR(dev), LCR_DLAB | lcr_cache);
INBYTE(RDR(dev)); INBYTE(RDR(dev));
OUTBYTE(LCR(dev), lcr_cache);
/* disable interrupts */ /* disable interrupts */
OUTBYTE(IER(dev), 0x00); OUTBYTE(IER(dev), 0x00);