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Subject[PATCH] 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>

--- linux-3.5-vanilla/drivers/tty/serial/cpm_uart/cpm_uart_core.c 2012-07-21 22:58:29.000000000 +0200
+++ linux-3.5/drivers/tty/serial/cpm_uart/cpm_uart_core.c 2012-08-09 17:38:37.000000000 +0200
@@ -501,6 +501,7 @@
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 @@
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 @@
* 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 @@
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);
}


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