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>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/tty/serial/cpm_uart/cpm_uart_core.c b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
index 7f6a1c7cb3de..d0dd9194cecc 100644
--- 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);
         }