From: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
DW based controllers like the one on Renesas RZ/N1 must be programmed as
flow controllers when using DMA.
* Table 11.45 of the system manual, "Flow Control Combinations", states
that using UART with DMA requires setting the DMA in the peripheral
flow controller mode regardless of the direction.
* Chapter 11.6.1.3 of the system manual, "Basic Interface Definitions",
explains that the burst size in the above case must be configured in
the peripheral's register DEST/SRC_BURST_SIZE.
Experiments shown that upon Rx timeout, the DMA transaction needed to be
manually cleared as well.
Signed-off-by: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
Co-developed-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_dw.c | 64 +++++++++++++++++++++++++++++++
1 file changed, 64 insertions(+)
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index ef3f05c82ad6..90e64c8bd4bf 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -34,16 +34,28 @@
/* Offsets for the DesignWare specific registers */
#define DW_UART_USR 0x1f /* UART Status Register */
+#define DW_UART_DMASA 0xa8 /* DMA Software Ack */
#define OCTEON_UART_USR 0x27 /* UART Status Register */
+#define RZN1_UART_TDMACR 0x10c /* DMA Control Register Transmit Mode */
+#define RZN1_UART_RDMACR 0x110 /* DMA Control Register Receive Mode */
+
/* DesignWare specific register fields */
#define DW_UART_MCR_SIRE BIT(6)
+/* Renesas specific register fields */
+#define RZN1_UART_xDMACR_DMA_EN BIT(0)
+#define RZN1_UART_xDMACR_1_WORD_BURST (0 << 1)
+#define RZN1_UART_xDMACR_4_WORD_BURST (1 << 1)
+#define RZN1_UART_xDMACR_8_WORD_BURST (3 << 1)
+#define RZN1_UART_xDMACR_BLK_SZ(x) ((x) << 3)
+
/* Quirks */
#define DW_UART_QUIRK_OCTEON BIT(0)
#define DW_UART_QUIRK_ARMADA_38X BIT(1)
#define DW_UART_QUIRK_SKIP_SET_RATE BIT(2)
+#define DW_UART_QUIRK_IS_DMA_FC BIT(3)
static inline struct dw8250_data *clk_to_dw8250_data(struct notifier_block *nb)
{
@@ -226,6 +238,7 @@ static int dw8250_handle_irq(struct uart_port *p)
struct dw8250_data *d = to_dw8250_data(p->private_data);
unsigned int iir = p->serial_in(p, UART_IIR);
bool rx_timeout = (iir & 0x3f) == UART_IIR_RX_TIMEOUT;
+ unsigned int quirks = d->pdata->quirks;
unsigned int status;
unsigned long flags;
@@ -249,6 +262,15 @@ static int dw8250_handle_irq(struct uart_port *p)
spin_unlock_irqrestore(&p->lock, flags);
}
+ /* Manually stop the Rx DMA transfer when acting as flow controller */
+ if (quirks & DW_UART_QUIRK_IS_DMA_FC && up->dma && up->dma->rx_running && rx_timeout) {
+ status = p->serial_in(p, UART_LSR);
+ if (status & (UART_LSR_DR | UART_LSR_BI)) {
+ dw8250_writel_ext(p, RZN1_UART_RDMACR, 0);
+ dw8250_writel_ext(p, DW_UART_DMASA, 1);
+ }
+ }
+
if (serial8250_handle_irq(p, iir))
return 1;
@@ -372,6 +394,42 @@ static bool dw8250_idma_filter(struct dma_chan *chan, void *param)
return param == chan->device->dev;
}
+static u32 dw8250_rzn1_get_dmacr_burst(int max_burst)
+{
+ if (max_burst >= 8)
+ return RZN1_UART_xDMACR_8_WORD_BURST;
+ else if (max_burst >= 4)
+ return RZN1_UART_xDMACR_4_WORD_BURST;
+ else
+ return RZN1_UART_xDMACR_1_WORD_BURST;
+}
+
+static void dw8250_prepare_tx_dma(struct uart_8250_port *p)
+{
+ struct uart_port *up = &p->port;
+ struct uart_8250_dma *dma = p->dma;
+ u32 val;
+
+ dw8250_writel_ext(up, RZN1_UART_TDMACR, 0);
+ val = dw8250_rzn1_get_dmacr_burst(dma->txconf.dst_maxburst) |
+ RZN1_UART_xDMACR_BLK_SZ(dma->tx_size) |
+ RZN1_UART_xDMACR_DMA_EN;
+ dw8250_writel_ext(up, RZN1_UART_TDMACR, val);
+}
+
+static void dw8250_prepare_rx_dma(struct uart_8250_port *p)
+{
+ struct uart_port *up = &p->port;
+ struct uart_8250_dma *dma = p->dma;
+ u32 val;
+
+ dw8250_writel_ext(up, RZN1_UART_RDMACR, 0);
+ val = dw8250_rzn1_get_dmacr_burst(dma->rxconf.src_maxburst) |
+ RZN1_UART_xDMACR_BLK_SZ(dma->rx_size) |
+ RZN1_UART_xDMACR_DMA_EN;
+ dw8250_writel_ext(up, RZN1_UART_RDMACR, val);
+}
+
static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
{
struct device_node *np = p->dev->of_node;
@@ -404,6 +462,12 @@ static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
p->serial_out = dw8250_serial_out38x;
if (quirks & DW_UART_QUIRK_SKIP_SET_RATE)
p->set_termios = dw8250_do_set_termios;
+ if (quirks & DW_UART_QUIRK_IS_DMA_FC) {
+ data->data.dma.txconf.device_fc = 1;
+ data->data.dma.rxconf.device_fc = 1;
+ data->data.dma.prepare_tx_dma = dw8250_prepare_tx_dma;
+ data->data.dma.prepare_rx_dma = dw8250_prepare_rx_dma;
+ }
} else if (acpi_dev_present("APMC0D08", NULL, -1)) {
p->iotype = UPIO_MEM32;
--
2.27.0
