serial: 8250_omap: workaround for IP errata

index d75a66c72750..20c5b9c4c288 100644
@@ -1285,7 +1285,7 @@ static int omap8250_runtime_suspend(struct device *dev)
 			return -EBUSY;
 	}
 
-	if (up->dma)
+	if (up->dma && up->dma->rxchan)
 		omap_8250_rx_dma(up, UART_IIR_RX_TIMEOUT);
 
 	priv->latency = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE;

@@ -1310,7 +1310,7 @@ static int omap8250_runtime_resume(struct device *dev)
 	if (loss_cntx)
 		omap8250_restore_regs(up);
 
-	if (up->dma)
+	if (up->dma && up->dma->rxchan)
 		omap_8250_rx_dma(up, 0);
 
 	priv->latency = priv->calc_latency;

index 20c5b9c4c288..d9c96b993a84 100644
@@ -232,6 +232,15 @@ static void omap8250_update_scr(struct uart_8250_port *up,
 	serial_out(up, UART_OMAP_SCR, priv->scr);
 }
 
+static void omap8250_update_mdr1(struct uart_8250_port *up,
+				 struct omap8250_priv *priv)
+{
+	if (priv->habit & UART_ERRATA_i202_MDR1_ACCESS)
+		omap_8250_mdr1_errataset(up, priv);
+	else
+		serial_out(up, UART_OMAP_MDR1, priv->mdr1);
+}
+
 static void omap8250_restore_regs(struct uart_8250_port *up)
 {
 	struct omap8250_priv *priv = up->port.private_data;

@@ -282,11 +291,9 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
 	serial_out(up, UART_XOFF1, priv->xoff);
 
 	serial_out(up, UART_LCR, up->lcr);
-	/* need mode A for FCR */
-	if (priv->habit & UART_ERRATA_i202_MDR1_ACCESS)
-		omap_8250_mdr1_errataset(up, priv);
-	else
-		serial_out(up, UART_OMAP_MDR1, priv->mdr1);
+
+	omap8250_update_mdr1(up, priv);
+
 	up->port.ops->set_mctrl(&up->port, up->port.mctrl);
 }
 

index d9c96b993a84..fff026f3d0bb 100644
@@ -16,6 +16,7 @@
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/of_gpio.h>
 #include <linux/of_irq.h>
 #include <linux/delay.h>

@@ -537,14 +538,14 @@ static void omap_serial_fill_features_erratas(struct uart_8250_port *up,
 
 	switch (revision) {
 	case OMAP_UART_REV_46:
-		priv->habit = UART_ERRATA_i202_MDR1_ACCESS;
+		priv->habit |= UART_ERRATA_i202_MDR1_ACCESS;
 		break;
 	case OMAP_UART_REV_52:
-		priv->habit = UART_ERRATA_i202_MDR1_ACCESS |
+		priv->habit |= UART_ERRATA_i202_MDR1_ACCESS |
 				OMAP_UART_WER_HAS_TX_WAKEUP;
 		break;
 	case OMAP_UART_REV_63:
-		priv->habit = UART_ERRATA_i202_MDR1_ACCESS |
+		priv->habit |= UART_ERRATA_i202_MDR1_ACCESS |
 			OMAP_UART_WER_HAS_TX_WAKEUP;
 		break;
 	default:

@@ -1061,6 +1062,17 @@ static int omap8250_no_handle_irq(struct uart_port *port)
 	return 0;
 }
 
+static const u8 am3352_habit = OMAP_DMA_TX_KICK;
+
+static const struct of_device_id omap8250_dt_ids[] = {
+	{ .compatible = "ti,omap2-uart" },
+	{ .compatible = "ti,omap3-uart" },
+	{ .compatible = "ti,omap4-uart" },
+	{ .compatible = "ti,am3352-uart", .data = &am3352_habit, },
+	{},
+};
+MODULE_DEVICE_TABLE(of, omap8250_dt_ids);
+
 static int omap8250_probe(struct platform_device *pdev)
 {
 	struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);

@@ -1125,11 +1137,17 @@ static int omap8250_probe(struct platform_device *pdev)
 	up.port.unthrottle = omap_8250_unthrottle;
 
 	if (pdev->dev.of_node) {
+		const struct of_device_id *id;
+
 		ret = of_alias_get_id(pdev->dev.of_node, "serial");
 
 		of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 				     &up.port.uartclk);
 		priv->wakeirq = irq_of_parse_and_map(pdev->dev.of_node, 1);
+
+		id = of_match_device(of_match_ptr(omap8250_dt_ids), &pdev->dev);
+		if (id && id->data)
+			priv->habit |= *(u8 *)id->data;
 	} else {
 		ret = pdev->id;
 	}

@@ -1374,14 +1392,6 @@ static const struct dev_pm_ops omap8250_dev_pm_ops = {
 	.complete       = omap8250_complete,
 };
 
-static const struct of_device_id omap8250_dt_ids[] = {
-	{ .compatible = "ti,omap2-uart" },
-	{ .compatible = "ti,omap3-uart" },
-	{ .compatible = "ti,omap4-uart" },
-	{},
-};
-MODULE_DEVICE_TABLE(of, omap8250_dt_ids);
-
 static struct platform_driver omap8250_platform_driver = {
 	.driver = {
 		.name		= "omap8250",

index fff026f3d0bb..a2ee75dee070 100644
@@ -33,6 +33,11 @@
 #define UART_ERRATA_i202_MDR1_ACCESS	(1 << 0)
 #define OMAP_UART_WER_HAS_TX_WAKEUP	(1 << 1)
 #define OMAP_DMA_TX_KICK		(1 << 2)
+/*
+ * See Advisory 21 in AM437x errata SPRZ408B, updated April 2015.
+ * The same errata is applicable to AM335x and DRA7x processors too.
+ */
+#define UART_ERRATA_CLOCK_DISABLE	(1 << 3)
 
 #define OMAP_UART_FCR_RX_TRIG		6
 #define OMAP_UART_FCR_TX_TRIG		4

@@ -54,6 +59,12 @@
 #define OMAP_UART_MVR_MAJ_SHIFT		8
 #define OMAP_UART_MVR_MIN_MASK		0x3f
 
+/* SYSC register bitmasks */
+#define OMAP_UART_SYSC_SOFTRESET	(1 << 1)
+
+/* SYSS register bitmasks */
+#define OMAP_UART_SYSS_RESETDONE	(1 << 0)
+
 #define UART_TI752_TLR_TX	0
 #define UART_TI752_TLR_RX	4
 

@@ -1062,13 +1073,15 @@ static int omap8250_no_handle_irq(struct uart_port *port)
 	return 0;
 }
 
-static const u8 am3352_habit = OMAP_DMA_TX_KICK;
+static const u8 am3352_habit = OMAP_DMA_TX_KICK | UART_ERRATA_CLOCK_DISABLE;
+static const u8 am4372_habit = UART_ERRATA_CLOCK_DISABLE;
 
 static const struct of_device_id omap8250_dt_ids[] = {
 	{ .compatible = "ti,omap2-uart" },
 	{ .compatible = "ti,omap3-uart" },
 	{ .compatible = "ti,omap4-uart" },
 	{ .compatible = "ti,am3352-uart", .data = &am3352_habit, },
+	{ .compatible = "ti,am4372-uart", .data = &am4372_habit, },
 	{},
 };
 MODULE_DEVICE_TABLE(of, omap8250_dt_ids);

@@ -1282,17 +1295,46 @@ static int omap8250_lost_context(struct uart_8250_port *up)
 {
 	u32 val;
 
-	val = serial_in(up, UART_OMAP_MDR1);
+	val = serial_in(up, UART_OMAP_SCR);
 	/*
-	 * If we lose context, then MDR1 is set to its reset value which is
-	 * UART_OMAP_MDR1_DISABLE. After set_termios() we set it either to 13x
-	 * or 16x but never to disable again.
+	 * If we lose context, then SCR is set to its reset value of zero.
+	 * After set_termios() we set bit 3 of SCR (TX_EMPTY_CTL_IT) to 1,
+	 * among other bits, to never set the register back to zero again.
 	 */
-	if (val == UART_OMAP_MDR1_DISABLE)
+	if (!val)
 		return 1;
 	return 0;
 }
 
+/* TODO: in future, this should happen via API in drivers/reset/ */
+static int omap8250_soft_reset(struct device *dev)
+{
+	struct omap8250_priv *priv = dev_get_drvdata(dev);
+	struct uart_8250_port *up = serial8250_get_port(priv->line);
+	int timeout = 100;
+	int sysc;
+	int syss;
+
+	sysc = serial_in(up, UART_OMAP_SYSC);
+
+	/* softreset the UART */
+	sysc |= OMAP_UART_SYSC_SOFTRESET;
+	serial_out(up, UART_OMAP_SYSC, sysc);
+
+	/* By experiments, 1us enough for reset complete on AM335x */
+	do {
+		udelay(1);
+		syss = serial_in(up, UART_OMAP_SYSS);
+	} while (--timeout && !(syss & OMAP_UART_SYSS_RESETDONE));
+
+	if (!timeout) {
+		dev_err(dev, "timed out waiting for reset done\n");
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
 static int omap8250_runtime_suspend(struct device *dev)
 {
 	struct omap8250_priv *priv = dev_get_drvdata(dev);

@@ -1310,6 +1352,17 @@ static int omap8250_runtime_suspend(struct device *dev)
 			return -EBUSY;
 	}
 
+	if (priv->habit & UART_ERRATA_CLOCK_DISABLE) {
+		int ret;
+
+		ret = omap8250_soft_reset(dev);
+		if (ret)
+			return ret;
+
+		/* Restore to UART mode after reset (for wakeup) */
+		omap8250_update_mdr1(up, priv);
+	}
+
 	if (up->dma && up->dma->rxchan)
 		omap_8250_rx_dma(up, UART_IIR_RX_TIMEOUT);
 

index a2ee75dee070..d9a37191a1ae 100644
@@ -1082,6 +1082,7 @@ static const struct of_device_id omap8250_dt_ids[] = {
 	{ .compatible = "ti,omap4-uart" },
 	{ .compatible = "ti,am3352-uart", .data = &am3352_habit, },
 	{ .compatible = "ti,am4372-uart", .data = &am4372_habit, },
+	{ .compatible = "ti,dra742-uart", .data = &am4372_habit, },
 	{},
 };
 MODULE_DEVICE_TABLE(of, omap8250_dt_ids);