[PATCH 5/7] serial: 8250_dw: Add a dma_capable bit to the platform data

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

From: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>

The CPR register can give the information whether the IP is DMA capable
or not. Let's extract this information and use it to discriminate when
the DMA can be hooked up or not.

Signed-off-by: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
---
 drivers/tty/serial/8250/8250_dw.c    | 4 ++--
 drivers/tty/serial/8250/8250_dwlib.c | 7 +++++--
 drivers/tty/serial/8250/8250_dwlib.h | 1 +
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 1f7a423d6ef2..c0f54284bc70 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -556,8 +556,8 @@ static int dw8250_probe(struct platform_device *pdev)
 	if (!data->skip_autocfg)
 		dw8250_setup_port(p);
 
-	/* If we have a valid fifosize, try hooking up DMA */
-	if (p->fifosize) {
+	/* If we have a valid fifosize and DMA support, try hooking up DMA */
+	if (p->fifosize && data->dma_capable) {
 		data->data.dma.rxconf.src_maxburst = p->fifosize / 4;
 		data->data.dma.txconf.dst_maxburst = p->fifosize / 4;
 		up->dma = &data->data.dma;
diff --git a/drivers/tty/serial/8250/8250_dwlib.c b/drivers/tty/serial/8250/8250_dwlib.c
index 5cf298c5a0f9..5ec7c12ed117 100644
--- a/drivers/tty/serial/8250/8250_dwlib.c
+++ b/drivers/tty/serial/8250/8250_dwlib.c
@@ -92,6 +92,8 @@ void dw8250_setup_port(struct uart_port *p)
 {
 	struct uart_8250_port *up = up_to_u8250p(p);
 	const struct dw8250_platform_data *plat = of_device_get_match_data(up->port.dev);
+	struct dw8250_port_data *d = p->private_data;
+	struct dw8250_data *data = container_of(d, struct dw8250_data, data);
 	u32 reg;
 
 	/*
@@ -110,8 +112,6 @@ void dw8250_setup_port(struct uart_port *p)
 	dw8250_writel_ext(p, DW_UART_DLF, 0);
 
 	if (reg) {
-		struct dw8250_port_data *d = p->private_data;
-
 		d->dlf_size = fls(reg);
 		p->get_divisor = dw8250_get_divisor;
 		p->set_divisor = dw8250_set_divisor;
@@ -138,5 +138,8 @@ void dw8250_setup_port(struct uart_port *p)
 
 	if (reg & DW_UART_CPR_SIR_MODE)
 		up->capabilities |= UART_CAP_IRDA;
+
+	if (reg & DW_UART_CPR_DMA_EXTRA)
+		data->dma_capable = 1;
 }
 EXPORT_SYMBOL_GPL(dw8250_setup_port);
diff --git a/drivers/tty/serial/8250/8250_dwlib.h b/drivers/tty/serial/8250/8250_dwlib.h
index ffce2744a28e..900b2321aff0 100644
--- a/drivers/tty/serial/8250/8250_dwlib.h
+++ b/drivers/tty/serial/8250/8250_dwlib.h
@@ -34,6 +34,7 @@ struct dw8250_data {
 
 	unsigned int		skip_autocfg:1;
 	unsigned int		uart_16550_compatible:1;
+	unsigned int		dma_capable:1;
 };
 
 void dw8250_do_set_termios(struct uart_port *p, struct ktermios *termios, struct ktermios *old);
-- 
2.27.0