[PATCH v5 14/14] tty: serial: qcom-geni-serial: add support for serial engine DMA

From: Bartosz Golaszewski
Date: Fri Dec 02 2022 - 03:58:20 EST

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From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

The qcom-geni-serial driver currently only works in SE FIFO mode. This
limits the UART speed to around 180 kB/s. In order to achieve higher
speeds we need to use SE DMA mode.

Keep the console port working in FIFO mode but extend the code to use DMA
for the high-speed port.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
---
drivers/tty/serial/qcom_geni_serial.c | 314 +++++++++++++++++++++-----
1 file changed, 255 insertions(+), 59 deletions(-)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 1dfc0122ff53..85c8771ae318 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -70,6 +70,8 @@
#define UART_START_TX 0x1
/* UART S_CMD OP codes */
#define UART_START_READ 0x1
+#define UART_PARAM 0x1
+#define UART_PARAM_RFR_OPEN BIT(7)

#define UART_OVERSAMPLING 32
#define STALE_TIMEOUT 16
@@ -95,9 +97,11 @@
/* We always configure 4 bytes per FIFO word */
#define BYTES_PER_FIFO_WORD 4U

+#define DMA_RX_BUF_SIZE 2048
+
struct qcom_geni_device_data {
bool console;
- void (*handle_rx)(struct uart_port *uport, u32 bytes, bool drop);
+ enum geni_se_xfer_mode mode;
};

struct qcom_geni_private_data {
@@ -118,9 +122,11 @@ struct qcom_geni_serial_port {
u32 tx_fifo_depth;
u32 tx_fifo_width;
u32 rx_fifo_depth;
+ dma_addr_t tx_dma_addr;
+ dma_addr_t rx_dma_addr;
bool setup;
unsigned int baud;
- void *rx_fifo;
+ void *rx_buf;
u32 loopback;
bool brk;

@@ -249,6 +255,16 @@ static struct qcom_geni_serial_port *get_port_from_line(int line, bool console)
return port;
}

+static bool qcom_geni_serial_main_active(struct uart_port *uport)
+{
+ return readl(uport->membase + SE_GENI_STATUS) & M_GENI_CMD_ACTIVE;
+}
+
+static bool qcom_geni_serial_secondary_active(struct uart_port *uport)
+{
+ return readl(uport->membase + SE_GENI_STATUS) & S_GENI_CMD_ACTIVE;
+}
+
static bool qcom_geni_serial_poll_bit(struct uart_port *uport,
int offset, int field, bool set)
{
@@ -552,18 +568,11 @@ static void handle_rx_console(struct uart_port *uport, u32 bytes, bool drop)

static void handle_rx_uart(struct uart_port *uport, u32 bytes, bool drop)
{
- struct tty_port *tport;
struct qcom_geni_serial_port *port = to_dev_port(uport);
- u32 num_bytes_pw = port->tx_fifo_width / BITS_PER_BYTE;
- u32 words = ALIGN(bytes, num_bytes_pw) / num_bytes_pw;
+ struct tty_port *tport = &uport->state->port;
int ret;

- tport = &uport->state->port;
- ioread32_rep(uport->membase + SE_GENI_RX_FIFOn, port->rx_fifo, words);
- if (drop)
- return;
-
- ret = tty_insert_flip_string(tport, port->rx_fifo, bytes);
+ ret = tty_insert_flip_string(tport, port->rx_buf, bytes);
if (ret != bytes) {
dev_err(uport->dev, "%s:Unable to push data ret %d_bytes %d\n",
__func__, ret, bytes);
@@ -578,16 +587,75 @@ static unsigned int qcom_geni_serial_tx_empty(struct uart_port *uport)
return !readl(uport->membase + SE_GENI_TX_FIFO_STATUS);
}

-static void qcom_geni_serial_start_tx(struct uart_port *uport)
+static void qcom_geni_serial_stop_tx_dma(struct uart_port *uport)
{
- u32 irq_en;
- u32 status;
+ struct qcom_geni_serial_port *port = to_dev_port(uport);
+ bool done;
+ u32 m_irq_en;
+
+ if (!qcom_geni_serial_main_active(uport))
+ return;
+
+ if (port->rx_dma_addr) {
+ geni_se_tx_dma_unprep(&port->se, port->tx_dma_addr,
+ port->tx_remaining);
+ port->tx_dma_addr = 0;
+ port->tx_remaining = 0;
+ }
+
+ m_irq_en = readl(uport->membase + SE_GENI_M_IRQ_EN);
+ writel(m_irq_en, uport->membase + SE_GENI_M_IRQ_EN);
+ geni_se_cancel_m_cmd(&port->se);
+
+ done = qcom_geni_serial_poll_bit(uport, SE_GENI_S_IRQ_STATUS,
+ S_CMD_CANCEL_EN, true);
+ if (!done) {
+ geni_se_abort_m_cmd(&port->se);
+ done = qcom_geni_serial_poll_bit(uport, SE_GENI_M_IRQ_STATUS,
+ M_CMD_ABORT_EN, true);
+ if (!done)
+ dev_err_ratelimited(uport->dev, "M_CMD_ABORT_EN not set");
+ writel(M_CMD_ABORT_EN, uport->membase + SE_GENI_M_IRQ_CLEAR);
+ }
+
+ writel(M_CMD_CANCEL_EN, uport->membase + SE_GENI_M_IRQ_CLEAR);
+}
+
+static void qcom_geni_serial_start_tx_dma(struct uart_port *uport)
+{
+ struct qcom_geni_serial_port *port = to_dev_port(uport);
+ struct circ_buf *xmit = &uport->state->xmit;
+ unsigned int xmit_size;
+ int ret;
+
+ if (port->tx_dma_addr)
+ return;
+
+ xmit_size = uart_circ_chars_pending(xmit);
+ if (xmit_size < WAKEUP_CHARS)
+ uart_write_wakeup(uport);

- status = readl(uport->membase + SE_GENI_STATUS);
- if (status & M_GENI_CMD_ACTIVE)
+ xmit_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+
+ qcom_geni_serial_setup_tx(uport, xmit_size);
+
+ ret = geni_se_tx_dma_prep(&port->se, &xmit->buf[xmit->tail],
+ xmit_size, &port->tx_dma_addr);
+ if (ret) {
+ dev_err(uport->dev, "unable to start TX SE DMA: %d\n", ret);
+ qcom_geni_serial_stop_tx_dma(uport);
return;
+ }
+
+ port->tx_remaining = xmit_size;
+}
+
+static void qcom_geni_serial_start_tx_fifo(struct uart_port *uport)
+{
+ u32 irq_en;

- if (!qcom_geni_serial_tx_empty(uport))
+ if (qcom_geni_serial_main_active(uport) ||
+ !qcom_geni_serial_tx_empty(uport))
return;

irq_en = readl(uport->membase + SE_GENI_M_IRQ_EN);
@@ -597,19 +665,17 @@ static void qcom_geni_serial_start_tx(struct uart_port *uport)
writel(irq_en, uport->membase + SE_GENI_M_IRQ_EN);
}

-static void qcom_geni_serial_stop_tx(struct uart_port *uport)
+static void qcom_geni_serial_stop_tx_fifo(struct uart_port *uport)
{
u32 irq_en;
- u32 status;
struct qcom_geni_serial_port *port = to_dev_port(uport);

irq_en = readl(uport->membase + SE_GENI_M_IRQ_EN);
irq_en &= ~(M_CMD_DONE_EN | M_TX_FIFO_WATERMARK_EN);
writel(0, uport->membase + SE_GENI_TX_WATERMARK_REG);
writel(irq_en, uport->membase + SE_GENI_M_IRQ_EN);
- status = readl(uport->membase + SE_GENI_STATUS);
/* Possible stop tx is called multiple times. */
- if (!(status & M_GENI_CMD_ACTIVE))
+ if (!qcom_geni_serial_main_active(uport))
return;

geni_se_cancel_m_cmd(&port->se);
@@ -623,14 +689,13 @@ static void qcom_geni_serial_stop_tx(struct uart_port *uport)
writel(M_CMD_CANCEL_EN, uport->membase + SE_GENI_M_IRQ_CLEAR);
}

-static void qcom_geni_serial_handle_rx(struct uart_port *uport, bool drop)
+static void qcom_geni_serial_handle_rx_fifo(struct uart_port *uport, bool drop)
{
u32 status;
u32 word_cnt;
u32 last_word_byte_cnt;
u32 last_word_partial;
u32 total_bytes;
- struct qcom_geni_serial_port *port = to_dev_port(uport);

status = readl(uport->membase + SE_GENI_RX_FIFO_STATUS);
word_cnt = status & RX_FIFO_WC_MSK;
@@ -645,13 +710,12 @@ static void qcom_geni_serial_handle_rx(struct uart_port *uport, bool drop)
total_bytes += last_word_byte_cnt;
else
total_bytes += BYTES_PER_FIFO_WORD;
- port->dev_data->handle_rx(uport, total_bytes, drop);
+ handle_rx_console(uport, total_bytes, drop);
}

-static void qcom_geni_serial_stop_rx(struct uart_port *uport)
+static void qcom_geni_serial_stop_rx_fifo(struct uart_port *uport)
{
u32 irq_en;
- u32 status;
struct qcom_geni_serial_port *port = to_dev_port(uport);
u32 s_irq_status;

@@ -663,9 +727,7 @@ static void qcom_geni_serial_stop_rx(struct uart_port *uport)
irq_en &= ~(M_RX_FIFO_WATERMARK_EN | M_RX_FIFO_LAST_EN);
writel(irq_en, uport->membase + SE_GENI_M_IRQ_EN);

- status = readl(uport->membase + SE_GENI_STATUS);
- /* Possible stop rx is called multiple times. */
- if (!(status & S_GENI_CMD_ACTIVE))
+ if (!qcom_geni_serial_secondary_active(uport))
return;

geni_se_cancel_s_cmd(&port->se);
@@ -678,23 +740,20 @@ static void qcom_geni_serial_stop_rx(struct uart_port *uport)
s_irq_status = readl(uport->membase + SE_GENI_S_IRQ_STATUS);
/* Flush the Rx buffer */
if (s_irq_status & S_RX_FIFO_LAST_EN)
- qcom_geni_serial_handle_rx(uport, true);
+ qcom_geni_serial_handle_rx_fifo(uport, true);
writel(s_irq_status, uport->membase + SE_GENI_S_IRQ_CLEAR);

- status = readl(uport->membase + SE_GENI_STATUS);
- if (status & S_GENI_CMD_ACTIVE)
+ if (qcom_geni_serial_secondary_active(uport))
qcom_geni_serial_abort_rx(uport);
}

-static void qcom_geni_serial_start_rx(struct uart_port *uport)
+static void qcom_geni_serial_start_rx_fifo(struct uart_port *uport)
{
u32 irq_en;
- u32 status;
struct qcom_geni_serial_port *port = to_dev_port(uport);

- status = readl(uport->membase + SE_GENI_STATUS);
- if (status & S_GENI_CMD_ACTIVE)
- qcom_geni_serial_stop_rx(uport);
+ if (qcom_geni_serial_secondary_active(uport))
+ qcom_geni_serial_stop_rx_fifo(uport);

geni_se_setup_s_cmd(&port->se, UART_START_READ, 0);

@@ -707,6 +766,94 @@ static void qcom_geni_serial_start_rx(struct uart_port *uport)
writel(irq_en, uport->membase + SE_GENI_M_IRQ_EN);
}

+static void qcom_geni_serial_stop_rx_dma(struct uart_port *uport)
+{
+ struct qcom_geni_serial_port *port = to_dev_port(uport);
+
+ if (!qcom_geni_serial_secondary_active(uport))
+ return;
+
+ geni_se_cancel_s_cmd(&port->se);
+ qcom_geni_serial_poll_bit(uport, SE_GENI_S_IRQ_STATUS,
+ S_CMD_CANCEL_EN, true);
+
+ if (qcom_geni_serial_secondary_active(uport))
+ qcom_geni_serial_abort_rx(uport);
+
+ if (port->rx_dma_addr) {
+ geni_se_rx_dma_unprep(&port->se, port->rx_dma_addr,
+ DMA_RX_BUF_SIZE);
+ port->rx_dma_addr = 0;
+ }
+}
+
+static void qcom_geni_serial_start_rx_dma(struct uart_port *uport)
+{
+ struct qcom_geni_serial_port *port = to_dev_port(uport);
+ int ret;
+
+ if (qcom_geni_serial_secondary_active(uport))
+ qcom_geni_serial_stop_rx_dma(uport);
+
+ geni_se_setup_s_cmd(&port->se, UART_START_READ, UART_PARAM_RFR_OPEN);
+
+ ret = geni_se_rx_dma_prep(&port->se, port->rx_buf,
+ DMA_RX_BUF_SIZE,
+ &port->rx_dma_addr);
+ if (ret) {
+ dev_err(uport->dev, "unable to start RX SE DMA: %d\n", ret);
+ qcom_geni_serial_stop_rx_dma(uport);
+ }
+}
+
+static void qcom_geni_serial_handle_rx_dma(struct uart_port *uport, bool drop)
+{
+ struct qcom_geni_serial_port *port = to_dev_port(uport);
+ u32 rx_in;
+ int ret;
+
+ if (!qcom_geni_serial_secondary_active(uport))
+ return;
+
+ if (!port->rx_dma_addr)
+ return;
+
+ geni_se_rx_dma_unprep(&port->se, port->rx_dma_addr, DMA_RX_BUF_SIZE);
+ port->rx_dma_addr = 0;
+
+ rx_in = readl(uport->membase + SE_DMA_RX_LEN_IN);
+ if (!rx_in) {
+ dev_warn(uport->dev, "serial engine reports 0 RX bytes in!\n");
+ return;
+ }
+
+ if (!drop)
+ handle_rx_uart(uport, rx_in, drop);
+
+ ret = geni_se_rx_dma_prep(&port->se, port->rx_buf,
+ DMA_RX_BUF_SIZE,
+ &port->rx_dma_addr);
+ if (ret) {
+ dev_err(uport->dev, "unable to start RX SE DMA: %d\n", ret);
+ qcom_geni_serial_stop_rx_dma(uport);
+ }
+}
+
+static void qcom_geni_serial_start_rx(struct uart_port *uport)
+{
+ uport->ops->start_rx(uport);
+}
+
+static void qcom_geni_serial_stop_rx(struct uart_port *uport)
+{
+ uport->ops->stop_rx(uport);
+}
+
+static void qcom_geni_serial_stop_tx(struct uart_port *uport)
+{
+ uport->ops->stop_tx(uport);
+}
+
static void qcom_geni_serial_send_chunk_fifo(struct uart_port *uport,
unsigned int chunk)
{
@@ -731,8 +878,8 @@ static void qcom_geni_serial_send_chunk_fifo(struct uart_port *uport,
}
}

-static void qcom_geni_serial_handle_tx(struct uart_port *uport, bool done,
- bool active)
+static void qcom_geni_serial_handle_tx_fifo(struct uart_port *uport,
+ bool done, bool active)
{
struct qcom_geni_serial_port *port = to_dev_port(uport);
struct circ_buf *xmit = &uport->state->xmit;
@@ -752,7 +899,7 @@ static void qcom_geni_serial_handle_tx(struct uart_port *uport, bool done,

/* All data has been transmitted and acknowledged as received */
if (!pending && !status && done) {
- qcom_geni_serial_stop_tx(uport);
+ qcom_geni_serial_stop_tx_fifo(uport);
goto out_write_wakeup;
}

@@ -795,12 +942,32 @@ static void qcom_geni_serial_handle_tx(struct uart_port *uport, bool done,
uart_write_wakeup(uport);
}

+static void qcom_geni_serial_handle_tx_dma(struct uart_port *uport)
+{
+ struct qcom_geni_serial_port *port = to_dev_port(uport);
+ struct circ_buf *xmit = &uport->state->xmit;
+
+ uart_xmit_advance(uport, port->tx_remaining);
+ geni_se_tx_dma_unprep(&port->se, port->tx_dma_addr, port->tx_remaining);
+ port->tx_dma_addr = 0;
+ port->tx_remaining = 0;
+
+ if (!uart_circ_empty(xmit))
+ qcom_geni_serial_start_tx_dma(uport);
+
+ if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+ uart_write_wakeup(uport);
+}
+
static irqreturn_t qcom_geni_serial_isr(int isr, void *dev)
{
u32 m_irq_en;
u32 m_irq_status;
u32 s_irq_status;
u32 geni_status;
+ u32 dma;
+ u32 dma_tx_status;
+ u32 dma_rx_status;
struct uart_port *uport = dev;
bool drop_rx = false;
struct tty_port *tport = &uport->state->port;
@@ -813,10 +980,15 @@ static irqreturn_t qcom_geni_serial_isr(int isr, void *dev)

m_irq_status = readl(uport->membase + SE_GENI_M_IRQ_STATUS);
s_irq_status = readl(uport->membase + SE_GENI_S_IRQ_STATUS);
+ dma_tx_status = readl(uport->membase + SE_DMA_TX_IRQ_STAT);
+ dma_rx_status = readl(uport->membase + SE_DMA_RX_IRQ_STAT);
geni_status = readl(uport->membase + SE_GENI_STATUS);
+ dma = readl(uport->membase + SE_GENI_DMA_MODE_EN);
m_irq_en = readl(uport->membase + SE_GENI_M_IRQ_EN);
writel(m_irq_status, uport->membase + SE_GENI_M_IRQ_CLEAR);
writel(s_irq_status, uport->membase + SE_GENI_S_IRQ_CLEAR);
+ writel(dma_tx_status, uport->membase + SE_DMA_TX_IRQ_CLR);
+ writel(dma_rx_status, uport->membase + SE_DMA_RX_IRQ_CLR);

if (WARN_ON(m_irq_status & M_ILLEGAL_CMD_EN))
goto out_unlock;
@@ -826,10 +998,6 @@ static irqreturn_t qcom_geni_serial_isr(int isr, void *dev)
tty_insert_flip_char(tport, 0, TTY_OVERRUN);
}

- if (m_irq_status & m_irq_en & (M_TX_FIFO_WATERMARK_EN | M_CMD_DONE_EN))
- qcom_geni_serial_handle_tx(uport, m_irq_status & M_CMD_DONE_EN,
- geni_status & M_GENI_CMD_ACTIVE);
-
if (s_irq_status & (S_GP_IRQ_0_EN | S_GP_IRQ_1_EN)) {
if (s_irq_status & S_GP_IRQ_0_EN)
uport->icount.parity++;
@@ -839,8 +1007,35 @@ static irqreturn_t qcom_geni_serial_isr(int isr, void *dev)
port->brk = true;
}

- if (s_irq_status & (S_RX_FIFO_WATERMARK_EN | S_RX_FIFO_LAST_EN))
- qcom_geni_serial_handle_rx(uport, drop_rx);
+ if (dma) {
+ if (dma_tx_status & TX_DMA_DONE)
+ qcom_geni_serial_handle_tx_dma(uport);
+
+ if (dma_rx_status) {
+ if (dma_rx_status & RX_RESET_DONE)
+ goto out_unlock;
+
+ if (dma_rx_status & RX_DMA_PARITY_ERR) {
+ uport->icount.parity++;
+ drop_rx = true;
+ }
+
+ if (dma_rx_status & RX_DMA_BREAK)
+ uport->icount.brk++;
+
+ if (dma_rx_status & (RX_DMA_DONE | RX_EOT))
+ qcom_geni_serial_handle_rx_dma(uport, drop_rx);
+ }
+ } else {
+ if (m_irq_status & m_irq_en &
+ (M_TX_FIFO_WATERMARK_EN | M_CMD_DONE_EN))
+ qcom_geni_serial_handle_tx_fifo(uport,
+ m_irq_status & M_CMD_DONE_EN,
+ geni_status & M_GENI_CMD_ACTIVE);
+
+ if (s_irq_status & (S_RX_FIFO_WATERMARK_EN | S_RX_FIFO_LAST_EN))
+ qcom_geni_serial_handle_rx_fifo(uport, drop_rx);
+ }

out_unlock:
uart_unlock_and_check_sysrq(uport);
@@ -909,7 +1104,7 @@ static int qcom_geni_serial_port_setup(struct uart_port *uport)
geni_se_config_packing(&port->se, BITS_PER_BYTE, BYTES_PER_FIFO_WORD,
false, true, true);
geni_se_init(&port->se, UART_RX_WM, port->rx_fifo_depth - 2);
- geni_se_select_mode(&port->se, GENI_SE_FIFO);
+ geni_se_select_mode(&port->se, port->dev_data->mode);
port->setup = true;

return 0;
@@ -1307,10 +1502,10 @@ static void qcom_geni_serial_pm(struct uart_port *uport,

static const struct uart_ops qcom_geni_console_pops = {
.tx_empty = qcom_geni_serial_tx_empty,
- .stop_tx = qcom_geni_serial_stop_tx,
- .start_tx = qcom_geni_serial_start_tx,
- .stop_rx = qcom_geni_serial_stop_rx,
- .start_rx = qcom_geni_serial_start_rx,
+ .stop_tx = qcom_geni_serial_stop_tx_fifo,
+ .start_tx = qcom_geni_serial_start_tx_fifo,
+ .stop_rx = qcom_geni_serial_stop_rx_fifo,
+ .start_rx = qcom_geni_serial_start_rx_fifo,
.set_termios = qcom_geni_serial_set_termios,
.startup = qcom_geni_serial_startup,
.request_port = qcom_geni_serial_request_port,
@@ -1328,9 +1523,10 @@ static const struct uart_ops qcom_geni_console_pops = {

static const struct uart_ops qcom_geni_uart_pops = {
.tx_empty = qcom_geni_serial_tx_empty,
- .stop_tx = qcom_geni_serial_stop_tx,
- .start_tx = qcom_geni_serial_start_tx,
- .stop_rx = qcom_geni_serial_stop_rx,
+ .stop_tx = qcom_geni_serial_stop_tx_dma,
+ .start_tx = qcom_geni_serial_start_tx_dma,
+ .start_rx = qcom_geni_serial_start_rx_dma,
+ .stop_rx = qcom_geni_serial_stop_rx_dma,
.set_termios = qcom_geni_serial_set_termios,
.startup = qcom_geni_serial_startup,
.request_port = qcom_geni_serial_request_port,
@@ -1399,9 +1595,9 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
port->tx_fifo_width = DEF_FIFO_WIDTH_BITS;

if (!data->console) {
- port->rx_fifo = devm_kcalloc(uport->dev,
- port->rx_fifo_depth, sizeof(u32), GFP_KERNEL);
- if (!port->rx_fifo)
+ port->rx_buf = devm_kzalloc(uport->dev,
+ DMA_RX_BUF_SIZE, GFP_KERNEL);
+ if (!port->rx_buf)
return -ENOMEM;
}

@@ -1531,12 +1727,12 @@ static int __maybe_unused qcom_geni_serial_sys_resume(struct device *dev)

static const struct qcom_geni_device_data qcom_geni_console_data = {
.console = true,
- .handle_rx = handle_rx_console,
+ .mode = GENI_SE_FIFO,
};

static const struct qcom_geni_device_data qcom_geni_uart_data = {
.console = false,
- .handle_rx = handle_rx_uart,
+ .mode = GENI_SE_DMA,
};

static const struct dev_pm_ops qcom_geni_serial_pm_ops = {
--
2.37.2

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