Powerpc 8xx CPM_UART setting MAXIDL register proportionaly to baud rate

MAXIDL is the timeout after which a receive buffer is closed when not full if
no more characters are received. We calculate it from the baudrate so that the
duration is always the same at standard rates: about 4ms. At 9600 bauds it gives
a timeout of 4 characters, which is the timeout on the 8250 UART.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/cpm_uart/cpm_uart_core.c b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
index 7f6a1c7..d0dd919 100644 (file)
--- a/drivers/tty/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
@@ -501,6 +501,7 @@ static void cpm_uart_set_termios(struct uart_port *port,
        struct uart_cpm_port *pinfo = (struct uart_cpm_port *)port;
        smc_t __iomem *smcp = pinfo->smcp;
        scc_t __iomem *sccp = pinfo->sccp;
+       int maxidl;
 
        pr_debug("CPM uart[%d]:set_termios\n", port->line);
 
@@ -511,6 +512,17 @@ static void cpm_uart_set_termios(struct uart_port *port,
        else
                pinfo->rx_fifosize = RX_BUF_SIZE;
 
+       /* MAXIDL is the timeout after which a receive buffer is closed
+        * when not full if no more characters are received.
+        * We calculate it from the baudrate so that the duration is
+        * always the same at standard rates: about 4ms.
+        */
+       maxidl = baud / 2400;
+       if (maxidl < 1)
+               maxidl = 1;
+       if (maxidl > 0x10)
+               maxidl = 0x10;
+
        /* Character length programmed into the mode register is the
         * sum of: 1 start bit, number of data bits, 0 or 1 parity bit,
         * 1 or 2 stop bits, minus 1.
@@ -611,6 +623,7 @@ static void cpm_uart_set_termios(struct uart_port *port,
                 * SMC/SCC receiver is disabled.
                 */
                out_be16(&pinfo->smcup->smc_mrblr, pinfo->rx_fifosize);
+               out_be16(&pinfo->smcup->smc_maxidl, maxidl);
 
                /* Set the mode register.  We want to keep a copy of the
                 * enables, because we want to put them back if they were
@@ -623,6 +636,7 @@ static void cpm_uart_set_termios(struct uart_port *port,
                    SMCMR_SM_UART | prev_mode);
        } else {
                out_be16(&pinfo->sccup->scc_genscc.scc_mrblr, pinfo->rx_fifosize);
+               out_be16(&pinfo->sccup->scc_maxidl, maxidl);
                out_be16(&sccp->scc_psmr, (sbits << 12) | scval);
        }