cpm1: don't send break on TX_STOP, don't interrupt RX/TX when adjusting termios parameters

Before setting STOP_TX, set _brkcr to 0 so the SMC does not send a break
character.  The driver appears to properly re-initialize _brkcr when the
SMC is restarted.

Do not interrupt RX/TX when the termios is being adjusted; it results in
corrupted characters appearing on the line.

Cc: Vitaly Bordug <vbordug@ru.mvista.com>
Cc: Scott Wood <scottwood@freescale.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/serial/cpm_uart/cpm_uart_core.c

@@ -435,10 +435,13 @@ static void cpm_uart_shutdown(struct uart_port *port)
 		}
 
 		/* Shut them really down and reinit buffer descriptors */
-		if (IS_SMC(pinfo))
+		if (IS_SMC(pinfo)) {
+			out_be16(&pinfo->smcup->smc_brkcr, 0);
 			cpm_line_cr_cmd(pinfo, CPM_CR_STOP_TX);
-		else
+		} else {
+			out_be16(&pinfo->sccup->scc_brkcr, 0);
 			cpm_line_cr_cmd(pinfo, CPM_CR_GRA_STOP_TX);
+		}
 
 		cpm_uart_initbd(pinfo);
 	}
@@ -554,9 +557,11 @@ static void cpm_uart_set_termios(struct uart_port *port,
 		 * enables, because we want to put them back if they were
 		 * present.
 		 */
-		prev_mode = in_be16(&smcp->smc_smcmr);
-		out_be16(&smcp->smc_smcmr, smcr_mk_clen(bits) | cval | SMCMR_SM_UART);
-		setbits16(&smcp->smc_smcmr, (prev_mode & (SMCMR_REN | SMCMR_TEN)));
+		prev_mode = in_be16(&smcp->smc_smcmr) & (SMCMR_REN | SMCMR_TEN);
+		/* Output in *one* operation, so we don't interrupt RX/TX if they
+		 * were already enabled. */
+		out_be16(&smcp->smc_smcmr, smcr_mk_clen(bits) | cval |
+		    SMCMR_SM_UART | prev_mode);
 	} else {
 		out_be16(&sccp->scc_psmr, (sbits << 12) | scval);
 	}
@@ -1198,12 +1203,14 @@ static int __init cpm_uart_console_setup(struct console *co, char *options)
 	udbg_putc = NULL;
 #endif
 
-	cpm_line_cr_cmd(pinfo, CPM_CR_STOP_TX);
-
 	if (IS_SMC(pinfo)) {
+		out_be16(&pinfo->smcup->smc_brkcr, 0);
+		cpm_line_cr_cmd(pinfo, CPM_CR_STOP_TX);
 		clrbits8(&pinfo->smcp->smc_smcm, SMCM_RX | SMCM_TX);
 		clrbits16(&pinfo->smcp->smc_smcmr, SMCMR_REN | SMCMR_TEN);
 	} else {
+		out_be16(&pinfo->sccup->scc_brkcr, 0);
+		cpm_line_cr_cmd(pinfo, CPM_CR_GRA_STOP_TX);
 		clrbits16(&pinfo->sccp->scc_sccm, UART_SCCM_TX | UART_SCCM_RX);
 		clrbits32(&pinfo->sccp->scc_gsmrl, SCC_GSMRL_ENR | SCC_GSMRL_ENT);
 	}