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Powerpc 8xx CPM_UART setting MAXIDL register proportionaly to baud rate

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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>
This commit is contained in:
Christophe Leroy 2012-09-24 08:39:44 +02:00 committed by Greg Kroah-Hartman
parent fbbb9d9646
commit 6e62bdc07e
1 changed files with 14 additions and 0 deletions
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14
drivers/tty/serial/cpm_uart/cpm_uart_core.c
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@ -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);
}