The Ingenic UART is similar to a standard 16550, but hardware flow control
requires setting a couple of additional, non-standard bits in the MCR.
The non-standard "modem control enable" and "hardware flow control
mode" bits are set when writing to the MCR register, based
on whether the modem control interrupt is active.
Additionally the non-16550 compliant parts of the uart need to be
masked from higher layers.
Tested on Ingenic JZ4780 on MIPS Creator Ci20 board
Signed-off-by: Matt Redfearn <matt.redfearn@xxxxxxxxxx>
---
drivers/tty/serial/8250/8250_ingenic.c | 41 ++++++++++++++++++++++++++++++++++
1 file changed, 41 insertions(+)
diff --git a/drivers/tty/serial/8250/8250_ingenic.c b/drivers/tty/serial/8250/8250_ingenic.c
index 21bf81fe794f..c5cde57e2da3 100644
--- a/drivers/tty/serial/8250/8250_ingenic.c
+++ b/drivers/tty/serial/8250/8250_ingenic.c
@@ -34,6 +34,9 @@ struct ingenic_uart_data {
#define UART_FCR_UME BIT(4)
+#define UART_MCR_MDCE BIT(7)
+#define UART_MCR_FCM BIT(6)
+
static struct earlycon_device *early_device;
static uint8_t __init early_in(struct uart_port *port, int offset)
@@ -129,6 +132,8 @@ OF_EARLYCON_DECLARE(jz4780_uart, "ingenic,jz4780-uart",
static void ingenic_uart_serial_out(struct uart_port *p, int offset, int value)
{
+ int ier;
+
switch (offset) {
case UART_FCR:
/* UART module enable */
@@ -136,9 +141,22 @@ static void ingenic_uart_serial_out(struct uart_port *p, int offset, int value)
break;
case UART_IER:
+ /* Enable receive timeout interrupt with the
+ * receive line status interrupt */
value |= (value & 0x4) << 2;
break;
+ case UART_MCR:
+ /* If we have enabled modem status IRQs we should enable modem
+ * mode. */
+ ier = p->serial_in(p, UART_IER);
+
+ if (ier & UART_IER_MSI)
+ value |= UART_MCR_MDCE | UART_MCR_FCM;
+ else
+ value &= ~(UART_MCR_MDCE | UART_MCR_FCM);
+ break;
+
default:
break;
}
@@ -146,6 +164,28 @@ static void ingenic_uart_serial_out(struct uart_port *p, int offset, int value)
writeb(value, p->membase + (offset << p->regshift));
}
+static unsigned int ingenic_uart_serial_in(struct uart_port *p, int offset)
+{
+ unsigned int value;
+
+ value = readb(p->membase + (offset << p->regshift));
+
+ /* Hide non-16550 compliant bits from higher levels */
+ switch (offset) {
+ case UART_FCR:
+ value &= ~UART_FCR_UME;
+ break;
+
+ case UART_MCR:
+ value &= ~(UART_MCR_MDCE | UART_MCR_FCM);
+ break;
+
+ default:
+ break;
+ }
+ return value;
+}
+
static int ingenic_uart_probe(struct platform_device *pdev)
{
struct uart_8250_port uart = {};
@@ -170,6 +210,7 @@ static int ingenic_uart_probe(struct platform_device *pdev)
uart.port.mapbase = regs->start;
uart.port.regshift = 2;
uart.port.serial_out = ingenic_uart_serial_out;
+ uart.port.serial_in = ingenic_uart_serial_in;
uart.port.irq = irq->start;
uart.port.dev = &pdev->dev;
--
2.1.4
--
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