[PATCH v2 4/4] serial: sprd: Add DMA mode support

From: Baolin Wang
Date: Mon Mar 04 2019 - 03:59:32 EST

From: Lanqing Liu <lanqing.liu@xxxxxxxxxx>

Add DMA mode support for the Spreadtrum serial controller.

Signed-off-by: Lanqing Liu <lanqing.liu@xxxxxxxxxx>
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
---
drivers/tty/serial/sprd_serial.c | 440 ++++++++++++++++++++++++++++++++++++--
1 file changed, 426 insertions(+), 14 deletions(-)

diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
index 8f45b66..6aebd77 100644
--- a/drivers/tty/serial/sprd_serial.c
+++ b/drivers/tty/serial/sprd_serial.c
@@ -10,6 +10,9 @@
#include <linux/clk.h>
#include <linux/console.h>
#include <linux/delay.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+#include <linux/dma/sprd-dma.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
@@ -75,6 +78,7 @@

/* control register 1 */
#define SPRD_CTL1 0x001C
+#define SPRD_DMA_EN BIT(15)
#define RX_HW_FLOW_CTL_THLD BIT(6)
#define RX_HW_FLOW_CTL_EN BIT(7)
#define TX_HW_FLOW_CTL_EN BIT(8)
@@ -86,6 +90,7 @@
#define THLD_TX_EMPTY 0x40
#define THLD_TX_EMPTY_SHIFT 8
#define THLD_RX_FULL 0x40
+#define THLD_RX_FULL_MASK GENMASK(6, 0)

/* config baud rate register */
#define SPRD_CLKD0 0x0024
@@ -102,15 +107,36 @@
#define SPRD_IMSR_TIMEOUT BIT(13)
#define SPRD_DEFAULT_SOURCE_CLK 26000000

+#define SPRD_RX_DMA_STEP 1
+#define SPRD_RX_FIFO_FULL 1
+#define SPRD_TX_FIFO_FULL 0x20
+#define SPRD_UART_RX_SIZE (UART_XMIT_SIZE / 4)
+
+struct sprd_uart_dma {
+ struct dma_chan *chn;
+ unsigned char *virt;
+ dma_addr_t phys_addr;
+ dma_cookie_t cookie;
+ u32 trans_len;
+ bool enable;
+};
+
struct sprd_uart_port {
struct uart_port port;
char name[16];
struct clk *clk;
+ struct sprd_uart_dma tx_dma;
+ struct sprd_uart_dma rx_dma;
+ dma_addr_t pos;
+ unsigned char *rx_buf_tail;
};

static struct sprd_uart_port *sprd_port[UART_NR_MAX];
static int sprd_ports_num;

+static int sprd_start_dma_rx(struct uart_port *port);
+static int sprd_tx_dma_config(struct uart_port *port);
+
static inline unsigned int serial_in(struct uart_port *port,
unsigned int offset)
{
@@ -141,45 +167,389 @@ static void sprd_set_mctrl(struct uart_port *port, unsigned int mctrl)
/* nothing to do */
}

-static void sprd_stop_tx(struct uart_port *port)
+static void sprd_stop_rx(struct uart_port *port)
{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
unsigned int ien, iclr;

+ if (sp->rx_dma.enable)
+ dmaengine_terminate_all(sp->rx_dma.chn);
+
iclr = serial_in(port, SPRD_ICLR);
ien = serial_in(port, SPRD_IEN);

- iclr |= SPRD_IEN_TX_EMPTY;
- ien &= ~SPRD_IEN_TX_EMPTY;
+ ien &= ~(SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT);
+ iclr |= SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT;

- serial_out(port, SPRD_ICLR, iclr);
serial_out(port, SPRD_IEN, ien);
+ serial_out(port, SPRD_ICLR, iclr);
}

-static void sprd_start_tx(struct uart_port *port)
+static void sprd_uart_dma_enable(struct uart_port *port, bool enable)
{
- unsigned int ien;
+ u32 val = serial_in(port, SPRD_CTL1);

- ien = serial_in(port, SPRD_IEN);
- if (!(ien & SPRD_IEN_TX_EMPTY)) {
- ien |= SPRD_IEN_TX_EMPTY;
- serial_out(port, SPRD_IEN, ien);
+ if (enable)
+ val |= SPRD_DMA_EN;
+ else
+ val &= ~SPRD_DMA_EN;
+
+ serial_out(port, SPRD_CTL1, val);
+}
+
+static void sprd_stop_tx_dma(struct uart_port *port)
+{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+ struct circ_buf *xmit = &port->state->xmit;
+ struct dma_tx_state state;
+ u32 trans_len;
+
+ dmaengine_pause(sp->tx_dma.chn);
+
+ dmaengine_tx_status(sp->tx_dma.chn, sp->tx_dma.cookie, &state);
+ if (state.residue) {
+ trans_len = state.residue - sp->tx_dma.phys_addr;
+ xmit->tail = (xmit->tail + trans_len) & (UART_XMIT_SIZE - 1);
+ port->icount.tx += trans_len;
+ dma_unmap_single(port->dev, sp->tx_dma.phys_addr,
+ sp->tx_dma.trans_len, DMA_TO_DEVICE);
}
+
+ dmaengine_terminate_all(sp->tx_dma.chn);
+ sp->tx_dma.trans_len = 0;
}

-static void sprd_stop_rx(struct uart_port *port)
+static int sprd_tx_buf_remap(struct uart_port *port)
+{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+ struct circ_buf *xmit = &port->state->xmit;
+
+ sp->tx_dma.trans_len =
+ CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+
+ sp->tx_dma.phys_addr = dma_map_single(port->dev,
+ (void *)&(xmit->buf[xmit->tail]),
+ sp->tx_dma.trans_len,
+ DMA_TO_DEVICE);
+ return dma_mapping_error(port->dev, sp->tx_dma.phys_addr);
+}
+
+static void sprd_complete_tx_dma(void *data)
+{
+ struct uart_port *port = (struct uart_port *)data;
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+ struct circ_buf *xmit = &port->state->xmit;
+ unsigned long flags;
+
+ spin_lock_irqsave(&port->lock, flags);
+ dma_unmap_single(port->dev, sp->tx_dma.phys_addr,
+ sp->tx_dma.trans_len, DMA_TO_DEVICE);
+
+ xmit->tail = (xmit->tail + sp->tx_dma.trans_len) & (UART_XMIT_SIZE - 1);
+ port->icount.tx += sp->tx_dma.trans_len;
+
+ if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+ uart_write_wakeup(port);
+
+ if (uart_circ_empty(xmit) || sprd_tx_buf_remap(port) ||
+ sprd_tx_dma_config(port))
+ sp->tx_dma.trans_len = 0;
+
+ spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static int sprd_uart_dma_submit(struct uart_port *port,
+ struct sprd_uart_dma *ud, u32 trans_len,
+ enum dma_transfer_direction direction,
+ dma_async_tx_callback callback)
{
+ struct dma_async_tx_descriptor *dma_des;
+ unsigned long flags;
+
+ flags = SPRD_DMA_FLAGS(SPRD_DMA_CHN_MODE_NONE,
+ SPRD_DMA_NO_TRG,
+ SPRD_DMA_FRAG_REQ,
+ SPRD_DMA_TRANS_INT);
+
+ dma_des = dmaengine_prep_slave_single(ud->chn, ud->phys_addr, trans_len,
+ direction, flags);
+ if (!dma_des)
+ return -ENODEV;
+
+ dma_des->callback = callback;
+ dma_des->callback_param = port;
+
+ ud->cookie = dmaengine_submit(dma_des);
+ if (dma_submit_error(ud->cookie))
+ return dma_submit_error(ud->cookie);
+
+ dma_async_issue_pending(ud->chn);
+
+ return 0;
+}
+
+static int sprd_tx_dma_config(struct uart_port *port)
+{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+ u32 burst = sp->tx_dma.trans_len > SPRD_TX_FIFO_FULL ?
+ SPRD_TX_FIFO_FULL : sp->tx_dma.trans_len;
+ int ret;
+ struct dma_slave_config cfg = {
+ .dst_addr = port->mapbase + SPRD_TXD,
+ .src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
+ .dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
+ .src_maxburst = burst,
+ };
+
+ ret = dmaengine_slave_config(sp->tx_dma.chn, &cfg);
+ if (ret < 0)
+ return ret;
+
+ return sprd_uart_dma_submit(port, &sp->tx_dma, sp->tx_dma.trans_len,
+ DMA_MEM_TO_DEV, sprd_complete_tx_dma);
+}
+
+static void sprd_start_tx_dma(struct uart_port *port)
+{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+ struct circ_buf *xmit = &port->state->xmit;
+
+ if (port->x_char) {
+ serial_out(port, SPRD_TXD, port->x_char);
+ port->icount.tx++;
+ port->x_char = 0;
+ return;
+ }
+
+ if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
+ sprd_stop_tx_dma(port);
+ return;
+ }
+
+ if (sp->tx_dma.trans_len)
+ return;
+
+ if (sprd_tx_buf_remap(port) || sprd_tx_dma_config(port))
+ sp->tx_dma.trans_len = 0;
+}
+
+static void sprd_rx_full_thld(struct uart_port *port, u32 thld)
+{
+ u32 val = serial_in(port, SPRD_CTL2);
+
+ val &= ~THLD_RX_FULL_MASK;
+ val |= thld & THLD_RX_FULL_MASK;
+ serial_out(port, SPRD_CTL2, val);
+}
+
+static int sprd_rx_alloc_buf(struct sprd_uart_port *sp)
+{
+ sp->rx_dma.virt = dma_alloc_coherent(sp->port.dev, SPRD_UART_RX_SIZE,
+ &sp->rx_dma.phys_addr, GFP_KERNEL);
+ if (!sp->rx_dma.virt)
+ return -ENOMEM;
+
+ return 0;
+}
+
+static void sprd_rx_free_buf(struct sprd_uart_port *sp)
+{
+ if (sp->rx_dma.virt)
+ dma_free_coherent(sp->port.dev, SPRD_UART_RX_SIZE,
+ sp->rx_dma.virt, sp->rx_dma.phys_addr);
+
+}
+
+static int sprd_rx_dma_config(struct uart_port *port, u32 burst)
+{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+ struct dma_slave_config cfg = {
+ .src_addr = port->mapbase + SPRD_RXD,
+ .src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
+ .dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
+ .src_maxburst = burst,
+ };
+
+ return dmaengine_slave_config(sp->rx_dma.chn, &cfg);
+}
+
+static void sprd_uart_dma_rx(struct uart_port *port)
+{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+ struct tty_port *tty = &port->state->port;
+
+ port->icount.rx += sp->rx_dma.trans_len;
+ tty_insert_flip_string(tty, sp->rx_buf_tail, sp->rx_dma.trans_len);
+ tty_flip_buffer_push(tty);
+}
+
+static void sprd_uart_dma_irq(struct uart_port *port)
+{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+ struct dma_tx_state state;
+ enum dma_status status;
+
+ status = dmaengine_tx_status(sp->rx_dma.chn,
+ sp->rx_dma.cookie, &state);
+ if (status == DMA_ERROR)
+ sprd_stop_rx(port);
+
+ if (!state.residue && sp->pos == sp->rx_dma.phys_addr)
+ return;
+
+ if (!state.residue) {
+ sp->rx_dma.trans_len = SPRD_UART_RX_SIZE +
+ sp->rx_dma.phys_addr - sp->pos;
+ sp->pos = sp->rx_dma.phys_addr;
+ } else {
+ sp->rx_dma.trans_len = state.residue - sp->pos;
+ sp->pos = state.residue;
+ }
+
+ sprd_uart_dma_rx(port);
+ sp->rx_buf_tail += sp->rx_dma.trans_len;
+}
+
+static void sprd_complete_rx_dma(void *data)
+{
+ struct uart_port *port = (struct uart_port *)data;
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+ struct dma_tx_state state;
+ enum dma_status status;
+ unsigned long flags;
+
+ spin_lock_irqsave(&port->lock, flags);
+
+ status = dmaengine_tx_status(sp->rx_dma.chn,
+ sp->rx_dma.cookie, &state);
+ if (status != DMA_COMPLETE) {
+ sprd_stop_rx(port);
+ spin_unlock_irqrestore(&port->lock, flags);
+ return;
+ }
+
+ if (sp->pos != sp->rx_dma.phys_addr) {
+ sp->rx_dma.trans_len = SPRD_UART_RX_SIZE +
+ sp->rx_dma.phys_addr - sp->pos;
+ sprd_uart_dma_rx(port);
+ sp->rx_buf_tail += sp->rx_dma.trans_len;
+ }
+
+ if (sprd_start_dma_rx(port))
+ sprd_stop_rx(port);
+
+ spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static int sprd_start_dma_rx(struct uart_port *port)
+{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+ int ret;
+
+ if (!sp->rx_dma.enable)
+ return 0;
+
+ sp->pos = sp->rx_dma.phys_addr;
+ sp->rx_buf_tail = sp->rx_dma.virt;
+ sprd_rx_full_thld(port, SPRD_RX_FIFO_FULL);
+ ret = sprd_rx_dma_config(port, SPRD_RX_DMA_STEP);
+ if (ret)
+ return ret;
+
+ return sprd_uart_dma_submit(port, &sp->rx_dma, SPRD_UART_RX_SIZE,
+ DMA_DEV_TO_MEM, sprd_complete_rx_dma);
+}
+
+static void sprd_release_dma(struct uart_port *port)
+{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+
+ sprd_uart_dma_enable(port, false);
+
+ if (sp->rx_dma.enable)
+ dma_release_channel(sp->rx_dma.chn);
+
+ if (sp->tx_dma.enable)
+ dma_release_channel(sp->tx_dma.chn);
+
+ sp->tx_dma.enable = false;
+ sp->rx_dma.enable = false;
+}
+
+static void sprd_request_dma(struct uart_port *port)
+{
+ struct sprd_uart_port *sp =
+ container_of(port, struct sprd_uart_port, port);
+
+ sp->tx_dma.enable = true;
+ sp->rx_dma.enable = true;
+
+ sp->tx_dma.chn = dma_request_chan(port->dev, "tx");
+ if (IS_ERR(sp->tx_dma.chn)) {
+ dev_err(port->dev, "request TX DMA channel failed, ret = %ld\n",
+ PTR_ERR(sp->tx_dma.chn));
+ sp->tx_dma.enable = false;
+ }
+
+ sp->rx_dma.chn = dma_request_chan(port->dev, "rx");
+ if (IS_ERR(sp->rx_dma.chn)) {
+ dev_err(port->dev, "request RX DMA channel failed, ret = %ld\n",
+ PTR_ERR(sp->tx_dma.chn));
+ sp->rx_dma.enable = false;
+ }
+}
+
+static void sprd_stop_tx(struct uart_port *port)
+{
+ struct sprd_uart_port *sp = container_of(port, struct sprd_uart_port,
+ port);
unsigned int ien, iclr;

+ if (sp->tx_dma.enable) {
+ sprd_stop_tx_dma(port);
+ return;
+ }
+
iclr = serial_in(port, SPRD_ICLR);
ien = serial_in(port, SPRD_IEN);

- ien &= ~(SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT);
- iclr |= SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT;
+ iclr |= SPRD_IEN_TX_EMPTY;
+ ien &= ~SPRD_IEN_TX_EMPTY;

serial_out(port, SPRD_IEN, ien);
serial_out(port, SPRD_ICLR, iclr);
}

+static void sprd_start_tx(struct uart_port *port)
+{
+ struct sprd_uart_port *sp = container_of(port, struct sprd_uart_port,
+ port);
+ unsigned int ien;
+
+ if (sp->tx_dma.enable) {
+ sprd_start_tx_dma(port);
+ return;
+ }
+
+ ien = serial_in(port, SPRD_IEN);
+ if (!(ien & SPRD_IEN_TX_EMPTY)) {
+ ien |= SPRD_IEN_TX_EMPTY;
+ serial_out(port, SPRD_IEN, ien);
+ }
+}
+
/* The Sprd serial does not support this function. */
static void sprd_break_ctl(struct uart_port *port, int break_state)
{
@@ -220,9 +590,16 @@ static int handle_lsr_errors(struct uart_port *port,

static inline void sprd_rx(struct uart_port *port)
{
+ struct sprd_uart_port *sp = container_of(port, struct sprd_uart_port,
+ port);
struct tty_port *tty = &port->state->port;
unsigned int ch, flag, lsr, max_count = SPRD_TIMEOUT;

+ if (sp->rx_dma.enable) {
+ sprd_uart_dma_irq(port);
+ return;
+ }
+
while ((serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK) &&
max_count--) {
lsr = serial_in(port, SPRD_LSR);
@@ -306,6 +683,25 @@ static irqreturn_t sprd_handle_irq(int irq, void *dev_id)
return IRQ_HANDLED;
}

+static void sprd_uart_dma_startup(struct uart_port *port,
+ struct sprd_uart_port *sp)
+{
+ int ret;
+
+ sprd_request_dma(port);
+ if (!(sp->rx_dma.enable || sp->tx_dma.enable))
+ return;
+
+ ret = sprd_start_dma_rx(port);
+ if (ret) {
+ sp->rx_dma.enable = false;
+ dma_release_channel(sp->rx_dma.chn);
+ dev_warn(port->dev, "fail to start RX dma mode\n");
+ }
+
+ sprd_uart_dma_enable(port, true);
+}
+
static int sprd_startup(struct uart_port *port)
{
int ret = 0;
@@ -334,6 +730,9 @@ static int sprd_startup(struct uart_port *port)
/* allocate irq */
sp = container_of(port, struct sprd_uart_port, port);
snprintf(sp->name, sizeof(sp->name), "sprd_serial%d", port->line);
+
+ sprd_uart_dma_startup(port, sp);
+
ret = devm_request_irq(port->dev, port->irq, sprd_handle_irq,
IRQF_SHARED, sp->name, port);
if (ret) {
@@ -348,7 +747,9 @@ static int sprd_startup(struct uart_port *port)
/* enable interrupt */
spin_lock_irqsave(&port->lock, flags);
ien = serial_in(port, SPRD_IEN);
- ien |= SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT | SPRD_IEN_TIMEOUT;
+ ien |= SPRD_IEN_BREAK_DETECT | SPRD_IEN_TIMEOUT;
+ if (!sp->rx_dma.enable)
+ ien |= SPRD_IEN_RX_FULL;
serial_out(port, SPRD_IEN, ien);
spin_unlock_irqrestore(&port->lock, flags);

@@ -357,6 +758,7 @@ static int sprd_startup(struct uart_port *port)

static void sprd_shutdown(struct uart_port *port)
{
+ sprd_release_dma(port);
serial_out(port, SPRD_IEN, 0);
serial_out(port, SPRD_ICLR, ~0);
devm_free_irq(port->dev, port->irq, port);
@@ -687,6 +1089,8 @@ static int sprd_remove(struct platform_device *dev)
if (!sprd_ports_num)
uart_unregister_driver(&sprd_uart_driver);

+ sprd_rx_free_buf(sup);
+
return 0;
}

@@ -775,6 +1179,14 @@ static int sprd_probe(struct platform_device *pdev)
}
up->irq = irq;

+ /*
+ * Allocate one dma buffer to prepare for receive transfer, in case
+ * memory allocation failure at runtime.
+ */
+ ret = sprd_rx_alloc_buf(sprd_port[index]);
+ if (ret)
+ return ret;
+
if (!sprd_ports_num) {
ret = uart_register_driver(&sprd_uart_driver);
if (ret < 0) {
--
1.7.9.5