diff mbox series

[v3,08/13] tty: serial: qcom-geni-serial: refactor qcom_geni_serial_handle_tx()

Message ID 20221123110759.1836666-9-brgl@bgdev.pl
State New
Headers
Series serial: qcom-geni-serial: implement support for SE DMA |

Commit Message

Bartosz Golaszewski Nov. 23, 2022, 11:07 a.m. UTC 
  From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

qcom_geni_serial_handle_tx() is pretty big, let's move the code that
handles the actual writing of data to a separate function which makes
sense in preparation for introducing a dma variant of handle_tx().

Let's also shuffle the code a bit, drop unneeded variables and use
uart_xmit_advance() instead of handling tail->xmit manually.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/tty/serial/qcom_geni_serial.c | 54 +++++++++++++--------------
 1 file changed, 27 insertions(+), 27 deletions(-)

Comments

Jiri Slaby Nov. 24, 2022, 7:18 a.m. UTC | #1 
On 23. 11. 22, 12:07, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> 
> qcom_geni_serial_handle_tx() is pretty big, let's move the code that
> handles the actual writing of data to a separate function which makes
> sense in preparation for introducing a dma variant of handle_tx().
> 
> Let's also shuffle the code a bit, drop unneeded variables and use
> uart_xmit_advance() instead of handling tail->xmit manually.
> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> ---
>   drivers/tty/serial/qcom_geni_serial.c | 54 +++++++++++++--------------
>   1 file changed, 27 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index 68a1402fbe58..658b6d596f58 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -704,19 +704,42 @@ static void qcom_geni_serial_start_rx(struct uart_port *uport)
>   	writel(irq_en, uport->membase + SE_GENI_M_IRQ_EN);
>   }

I know you just shuffle the code, but:

> +static void qcom_geni_serial_send_chunk_fifo(struct uart_port *uport,
> +					     unsigned int chunk)
> +{
> +	struct qcom_geni_serial_port *port = to_dev_port(uport);
> +	struct circ_buf *xmit = &uport->state->xmit;
> +	u8 buf[BYTES_PER_FIFO_WORD];
> +	size_t remaining = chunk;

Why size_t when the others are uints? Well, BYTES_PER_FIFO_WORD should 
be defined as 4U.

> +	unsigned int tx_bytes;
> +	int c;
> +
> +	while (remaining) {
> +		memset(buf, 0, sizeof(buf));
> +		tx_bytes = min_t(size_t, remaining, BYTES_PER_FIFO_WORD);

Then, no need for min_t.

> +
> +		for (c = 0; c < tx_bytes ; c++) {
> +			buf[c] = xmit->buf[xmit->tail];
> +			uart_xmit_advance(uport, 1);
> +		}
> +
> +		iowrite32_rep(uport->membase + SE_GENI_TX_FIFOn, buf, 1);

I wonder, why is _rep variant used to transfer a single word? Only to 
hide the cast?

thanks,
Bartosz Golaszewski Nov. 24, 2022, 2:51 p.m. UTC | #2 
On Thu, Nov 24, 2022 at 8:18 AM Jiri Slaby <jirislaby@kernel.org> wrote:
>
> On 23. 11. 22, 12:07, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > qcom_geni_serial_handle_tx() is pretty big, let's move the code that
> > handles the actual writing of data to a separate function which makes
> > sense in preparation for introducing a dma variant of handle_tx().
> >
> > Let's also shuffle the code a bit, drop unneeded variables and use
> > uart_xmit_advance() instead of handling tail->xmit manually.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > ---
> >   drivers/tty/serial/qcom_geni_serial.c | 54 +++++++++++++--------------
> >   1 file changed, 27 insertions(+), 27 deletions(-)
> >
> > diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> > index 68a1402fbe58..658b6d596f58 100644
> > --- a/drivers/tty/serial/qcom_geni_serial.c
> > +++ b/drivers/tty/serial/qcom_geni_serial.c
> > @@ -704,19 +704,42 @@ static void qcom_geni_serial_start_rx(struct uart_port *uport)
> >       writel(irq_en, uport->membase + SE_GENI_M_IRQ_EN);
> >   }
>
> I know you just shuffle the code, but:
>
> > +static void qcom_geni_serial_send_chunk_fifo(struct uart_port *uport,
> > +                                          unsigned int chunk)
> > +{
> > +     struct qcom_geni_serial_port *port = to_dev_port(uport);
> > +     struct circ_buf *xmit = &uport->state->xmit;
> > +     u8 buf[BYTES_PER_FIFO_WORD];
> > +     size_t remaining = chunk;
>
> Why size_t when the others are uints? Well, BYTES_PER_FIFO_WORD should
> be defined as 4U.

Good point.

>
> > +     unsigned int tx_bytes;
> > +     int c;
> > +
> > +     while (remaining) {
> > +             memset(buf, 0, sizeof(buf));
> > +             tx_bytes = min_t(size_t, remaining, BYTES_PER_FIFO_WORD);
>
> Then, no need for min_t.
>

Same.

> > +
> > +             for (c = 0; c < tx_bytes ; c++) {
> > +                     buf[c] = xmit->buf[xmit->tail];
> > +                     uart_xmit_advance(uport, 1);
> > +             }
> > +
> > +             iowrite32_rep(uport->membase + SE_GENI_TX_FIFOn, buf, 1);
>
> I wonder, why is _rep variant used to transfer a single word? Only to
> hide the cast?
>

Even if - using writel() with a cast doesn't seem to improve the
performance and this one looks prettier IMO.

Bartosz
diff mbox series

Patch

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 68a1402fbe58..658b6d596f58 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -704,19 +704,42 @@  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_send_chunk_fifo(struct uart_port *uport,
+					     unsigned int chunk)
+{
+	struct qcom_geni_serial_port *port = to_dev_port(uport);
+	struct circ_buf *xmit = &uport->state->xmit;
+	u8 buf[BYTES_PER_FIFO_WORD];
+	size_t remaining = chunk;
+	unsigned int tx_bytes;
+	int c;
+
+	while (remaining) {
+		memset(buf, 0, sizeof(buf));
+		tx_bytes = min_t(size_t, remaining, BYTES_PER_FIFO_WORD);
+
+		for (c = 0; c < tx_bytes ; c++) {
+			buf[c] = xmit->buf[xmit->tail];
+			uart_xmit_advance(uport, 1);
+		}
+
+		iowrite32_rep(uport->membase + SE_GENI_TX_FIFOn, buf, 1);
+
+		remaining -= tx_bytes;
+		port->tx_remaining -= tx_bytes;
+	}
+}
+
 static void qcom_geni_serial_handle_tx(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;
 	size_t avail;
-	size_t remaining;
 	size_t pending;
-	int i;
 	u32 status;
 	u32 irq_en;
 	unsigned int chunk;
-	int tail;
 
 	status = readl(uport->membase + SE_GENI_TX_FIFO_STATUS);
 
@@ -735,7 +758,6 @@  static void qcom_geni_serial_handle_tx(struct uart_port *uport, bool done,
 	avail = port->tx_fifo_depth - (status & TX_FIFO_WC);
 	avail *= BYTES_PER_FIFO_WORD;
 
-	tail = xmit->tail;
 	chunk = min(avail, pending);
 	if (!chunk)
 		goto out_write_wakeup;
@@ -750,29 +772,7 @@  static void qcom_geni_serial_handle_tx(struct uart_port *uport, bool done,
 					uport->membase + SE_GENI_M_IRQ_EN);
 	}
 
-	remaining = chunk;
-	for (i = 0; i < chunk; ) {
-		unsigned int tx_bytes;
-		u8 buf[sizeof(u32)];
-		int c;
-
-		memset(buf, 0, sizeof(buf));
-		tx_bytes = min_t(size_t, remaining, BYTES_PER_FIFO_WORD);
-
-		for (c = 0; c < tx_bytes ; c++) {
-			buf[c] = xmit->buf[tail++];
-			tail &= UART_XMIT_SIZE - 1;
-		}
-
-		iowrite32_rep(uport->membase + SE_GENI_TX_FIFOn, buf, 1);
-
-		i += tx_bytes;
-		uport->icount.tx += tx_bytes;
-		remaining -= tx_bytes;
-		port->tx_remaining -= tx_bytes;
-	}
-
-	xmit->tail = tail;
+	qcom_geni_serial_send_chunk_fifo(uport, chunk);
 
 	/*
 	 * The tx fifo watermark is level triggered and latched. Though we had