tty: serial: fsl_lpuart: add 7-bits format support on imx7ulp/imx8ulp/imx8qxp

imx7ulp/imx8ulp/imx8qxp lpuart IP support 7-bits format and have no
limitation on parity when CS7. Remove this limitation and add 7-bits
format support on imx7ulp/imx8ulp/imx8qxp.

Signed-off-by: Luke Wang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Luke Wang

drivers/tty/serial/fsl_lpuart.c

@@ -184,6 +184,7 @@
 #define UARTCTRL_SBK		0x00010000
 #define UARTCTRL_MA1IE		0x00008000
 #define UARTCTRL_MA2IE		0x00004000
+#define UARTCTRL_M7		0x00000800
 #define UARTCTRL_IDLECFG	GENMASK(10, 8)
 #define UARTCTRL_LOOPS		0x00000080
 #define UARTCTRL_DOZEEN		0x00000040
@@ -2222,8 +2223,9 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios,
 	modem = lpuart32_read(&sport->port, UARTMODIR);
 	sport->is_cs7 = false;
 	/*
-	 * only support CS8 and CS7, and for CS7 must enable PE.
+	 * only support CS8 and CS7
 	 * supported mode:
+	 *  - (7,n,1) (imx only)
 	 *  - (7,e/o,1)
 	 *  - (8,n,1)
 	 *  - (8,m/s,1)
@@ -2238,7 +2240,7 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios,
 
 	if ((termios->c_cflag & CSIZE) == CS8 ||
 		(termios->c_cflag & CSIZE) == CS7)
-		ctrl = old_ctrl & ~UARTCTRL_M;
+		ctrl = old_ctrl & ~(UARTCTRL_M | UARTCTRL_M7);
 
 	if (termios->c_cflag & CMSPAR) {
 		if ((termios->c_cflag & CSIZE) != CS8) {
@@ -2265,9 +2267,18 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios,
 	else
 		bd &= ~UARTBAUD_SBNS;
 
-	/* parity must be enabled when CS7 to match 8-bits format */
-	if ((termios->c_cflag & CSIZE) == CS7)
-		termios->c_cflag |= PARENB;
+	/*
+	 * imx support 7-bits format, no limitation on parity when CS7
+	 * for layerscape, parity must be enabled when CS7 to match 8-bits format
+	 */
+	if ((termios->c_cflag & CSIZE) == CS7 && !(termios->c_cflag & PARENB)) {
+		if (is_imx7ulp_lpuart(sport) ||
+		    is_imx8ulp_lpuart(sport) ||
+		    is_imx8qxp_lpuart(sport))
+			ctrl |= UARTCTRL_M7;
+		else
+			termios->c_cflag |= PARENB;
+	}
 
 	if ((termios->c_cflag & PARENB)) {
 		if (termios->c_cflag & CMSPAR) {