Patch "serial: imx: setup DCEDTE early and ensure DCD and RI irqs to be off" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    serial: imx: setup DCEDTE early and ensure DCD and RI irqs to be off

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     serial-imx-setup-dcedte-early-and-ensure-dcd-and-ri-irqs-to-be-off.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Sun Mar 18 16:55:33 CET 2018
From: "Uwe Kleine-K�nig" <u.kleine-koenig@pengutronix.de>
Date: Tue, 4 Apr 2017 11:18:51 +0200
Subject: serial: imx: setup DCEDTE early and ensure DCD and RI irqs to be off

From: "Uwe Kleine-K�nig" <u.kleine-koenig@pengutronix.de>


[ Upstream commit e61c38d85b7392e033ee03bca46f1d6006156175 ]

If the UART is operated in DTE mode and UCR3_DCD or UCR3_RI are 1 (which
is the reset default) and the opposite side pulls the respective line to
its active level the irq triggers after it is requested in .probe.

These irqs were already disabled in .startup but this might be too late.

Also setup of the UFCR_DCEDTE bit (currently done in .set_termios) is
done very late which is critical as it also controls direction of some
pins.

So setup UFCR_DCEDTE earlier (in .probe) and also disable the broken
irqs in DTE mode there before requesting irqs.

Acked-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/imx.c |   36 +++++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 13 deletions(-)

--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1316,19 +1316,10 @@ static int imx_startup(struct uart_port
 	if (!is_imx1_uart(sport)) {
 		temp = readl(sport->port.membase + UCR3);
 
-		/*
-		 * The effect of RI and DCD differs depending on the UFCR_DCEDTE
-		 * bit. In DCE mode they control the outputs, in DTE mode they
-		 * enable the respective irqs. At least the DCD irq cannot be
-		 * cleared on i.MX25 at least, so it's not usable and must be
-		 * disabled. I don't have test hardware to check if RI has the
-		 * same problem but I consider this likely so it's disabled for
-		 * now, too.
-		 */
-		temp |= IMX21_UCR3_RXDMUXSEL | UCR3_ADNIMP |
-			UCR3_DTRDEN | UCR3_RI | UCR3_DCD;
+		temp |= UCR3_DTRDEN | UCR3_RI | UCR3_DCD;
 
 		if (sport->dte_mode)
+			/* disable broken interrupts */
 			temp &= ~(UCR3_RI | UCR3_DCD);
 
 		writel(temp, sport->port.membase + UCR3);
@@ -1583,8 +1574,6 @@ imx_set_termios(struct uart_port *port,
 
 	ufcr = readl(sport->port.membase + UFCR);
 	ufcr = (ufcr & (~UFCR_RFDIV)) | UFCR_RFDIV_REG(div);
-	if (sport->dte_mode)
-		ufcr |= UFCR_DCEDTE;
 	writel(ufcr, sport->port.membase + UFCR);
 
 	writel(num, sport->port.membase + UBIR);
@@ -2149,6 +2138,27 @@ static int serial_imx_probe(struct platf
 		 UCR1_TXMPTYEN | UCR1_RTSDEN);
 	writel_relaxed(reg, sport->port.membase + UCR1);
 
+	if (!is_imx1_uart(sport) && sport->dte_mode) {
+		/*
+		 * The DCEDTE bit changes the direction of DSR, DCD, DTR and RI
+		 * and influences if UCR3_RI and UCR3_DCD changes the level of RI
+		 * and DCD (when they are outputs) or enables the respective
+		 * irqs. So set this bit early, i.e. before requesting irqs.
+		 */
+		writel(UFCR_DCEDTE, sport->port.membase + UFCR);
+
+		/*
+		 * Disable UCR3_RI and UCR3_DCD irqs. They are also not
+		 * enabled later because they cannot be cleared
+		 * (confirmed on i.MX25) which makes them unusable.
+		 */
+		writel(IMX21_UCR3_RXDMUXSEL | UCR3_ADNIMP | UCR3_DSR,
+		       sport->port.membase + UCR3);
+
+	} else {
+		writel(0, sport->port.membase + UFCR);
+	}
+
 	clk_disable_unprepare(sport->clk_ipg);
 
 	/*


Patches currently in stable-queue which might be from u.kleine-koenig@pengutronix.de are

queue-4.9/serial-imx-setup-dcedte-early-and-ensure-dcd-and-ri-irqs-to-be-off.patch