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char/cadence_uart: Fix can_receive logic 

The can_receive logic was only taking into account the RxFIFO
occupancy. RxFIFO population is only used for the echo and normal modes
however. Improve the logic to correctly return the true number of
receivable characters based on the current mode:

Normal mode: RxFIFO vacancy.
Remote loopback: TxFIFO vacancy.
Echo mode: The min of the TxFIFO and RxFIFO vacancies.
Local Loopback: Return non-zero (to implement droppage)

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: 36a58440c9ca5080151e95765c2c81342de8a8df.1388626249.git.peter.crosthwaite@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Peter Crosthwaite 2014-01-06 10:16:39 +00:00 committed by Peter Maydell
parent 2152e08ad1
commit d0ac820fe4
1 changed files with 9 additions and 1 deletions
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10
hw/char/cadence_uart.c
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@ -233,8 +233,16 @@ static void uart_parameters_setup(UartState *s)
static int uart_can_receive(void *opaque) static int uart_can_receive(void *opaque)
{ {
UartState *s = (UartState *)opaque; UartState *s = (UartState *)opaque;
int ret = MAX(RX_FIFO_SIZE, TX_FIFO_SIZE);
uint32_t ch_mode = s->r[R_MR] & UART_MR_CHMODE;
return RX_FIFO_SIZE - s->rx_count; if (ch_mode == NORMAL_MODE || ch_mode == ECHO_MODE) {
ret = MIN(ret, RX_FIFO_SIZE - s->rx_count);
}
if (ch_mode == REMOTE_LOOPBACK || ch_mode == ECHO_MODE) {
ret = MIN(ret, TX_FIFO_SIZE - s->tx_count);
}
return ret;
} }
static void uart_ctrl_update(UartState *s) static void uart_ctrl_update(UartState *s)