Commit 8d6fbe9b authored by Axel Haslam's avatar Axel Haslam Committed by Greg Kroah-Hartman
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greybus: uart: Use a fifo to send data to the modules 



The firmware now buffers data instead of blocking while the transfer
is sent, and the write operation cannot sleep.

Instead of using gb_transfer_sync (which sleeps) in the write callback,
buffer data in a fifo and send it from from a work queue.

The write_room callback will will report 1 byte less that what is really
available in the fifo, to leave space for extra characters that may
be added by the tty layer.

Signed-off-by: default avatarAxel Haslam <ahaslam@baylibre.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@google.com>
parent 219ffcf3

drivers/staging/greybus/uart.c

+105 −18
Original line number Diff line number Diff line
@@ -27,6 +27,8 @@ 
#include <linux/idr.h>

#include <linux/fs.h>

#include <linux/kdev_t.h>

#include <linux/kfifo.h>

#include <linux/workqueue.h>



#include "greybus.h"

#include "gbphy.h"
@@ -34,6 +36,9 @@ 
#define GB_NUM_MINORS	16	/* 16 is is more than enough */

#define GB_NAME		"ttyGB"



#define GB_UART_WRITE_FIFO_SIZE		PAGE_SIZE

#define GB_UART_WRITE_ROOM_MARGIN	1	/* leave some space in fifo */



struct gb_tty_line_coding {

	__le32	rate;

	__u8	format;
@@ -61,6 +66,9 @@ struct gb_tty { 
	u8 ctrlin;	/* input control lines */

	u8 ctrlout;	/* output control lines */

	struct gb_tty_line_coding line_coding;

	struct work_struct tx_work;

	struct kfifo write_fifo;

	bool close_pending;

};



static struct tty_driver *gb_tty_driver;
@@ -166,25 +174,52 @@ static int gb_uart_request_handler(struct gb_operation *op) 
	return ret;

}



static int send_data(struct gb_tty *tty, u16 size, const u8 *data)

static void  gb_uart_tx_write_work(struct work_struct *work)

{

	struct gb_uart_send_data_request *request;

	struct gb_tty *gb_tty;

	unsigned long flags;

	unsigned int send_size;

	int ret;



	if (!data || !size)

		return 0;

	gb_tty = container_of(work, struct gb_tty, tx_work);

	request = gb_tty->buffer;



	if (size > tty->buffer_payload_max)

		size = tty->buffer_payload_max;

	request = tty->buffer;

	request->size = cpu_to_le16(size);

	memcpy(&request->data[0], data, size);

	ret = gb_operation_sync(tty->connection, GB_UART_TYPE_SEND_DATA,

				request, sizeof(*request) + size, NULL, 0);

	if (ret)

		return ret;

	else

		return size;

	while (1) {

		if (gb_tty->close_pending)

			break;



		spin_lock_irqsave(&gb_tty->write_lock, flags);

		send_size = kfifo_out_peek(&gb_tty->write_fifo,

					&request->data[0],

					gb_tty->buffer_payload_max);

		if (!send_size) {

			spin_unlock_irqrestore(&gb_tty->write_lock, flags);

			break;

		}



		spin_unlock_irqrestore(&gb_tty->write_lock, flags);



		request->size = cpu_to_le16(send_size);

		ret = gb_operation_sync(gb_tty->connection,

					GB_UART_TYPE_SEND_DATA,

					request, sizeof(*request) + send_size,

					NULL, 0);

		if (ret) {

			dev_err(&gb_tty->gbphy_dev->dev,

				"send data error: %d\n", ret);

			if (!gb_tty->close_pending)

				schedule_work(work);

			return;

		}



		spin_lock_irqsave(&gb_tty->write_lock, flags);

		ret = kfifo_out(&gb_tty->write_fifo, &request->data[0],

				send_size);

		spin_unlock_irqrestore(&gb_tty->write_lock, flags);



		tty_port_tty_wakeup(&gb_tty->port);

	}

}



static int send_line_coding(struct gb_tty *tty)
@@ -318,19 +353,42 @@ static int gb_tty_write(struct tty_struct *tty, const unsigned char *buf, 
{

	struct gb_tty *gb_tty = tty->driver_data;



	return send_data(gb_tty, count, buf);

	count =  kfifo_in_spinlocked(&gb_tty->write_fifo, buf, count,

					&gb_tty->write_lock);

	if (count && !gb_tty->close_pending)

		schedule_work(&gb_tty->tx_work);



	return count;

}



static int gb_tty_write_room(struct tty_struct *tty)

{

	struct gb_tty *gb_tty = tty->driver_data;

	unsigned long flags;

	int room;



	spin_lock_irqsave(&gb_tty->write_lock, flags);

	room = kfifo_avail(&gb_tty->write_fifo);

	spin_unlock_irqrestore(&gb_tty->write_lock, flags);



	return gb_tty->buffer_payload_max;

	room -= GB_UART_WRITE_ROOM_MARGIN;

	if (room < 0)

		return 0;



	return room;

}



static int gb_tty_chars_in_buffer(struct tty_struct *tty)

{

	return 0;

	struct gb_tty *gb_tty = tty->driver_data;

	unsigned long flags;

	int chars;



	spin_lock_irqsave(&gb_tty->write_lock, flags);

	chars = kfifo_len(&gb_tty->write_fifo);

	spin_unlock_irqrestore(&gb_tty->write_lock, flags);



	return chars;

}



static int gb_tty_break_ctl(struct tty_struct *tty, int state)
@@ -621,6 +679,24 @@ static void gb_tty_dtr_rts(struct tty_port *port, int on) 
	send_control(gb_tty, newctrl);

}



static void gb_tty_port_shutdown(struct tty_port *port)

{

	struct gb_tty *gb_tty;

	unsigned long flags;



	gb_tty = container_of(port, struct gb_tty, port);



	gb_tty->close_pending = true;



	cancel_work_sync(&gb_tty->tx_work);



	spin_lock_irqsave(&gb_tty->write_lock, flags);

	kfifo_reset_out(&gb_tty->write_fifo);

	spin_unlock_irqrestore(&gb_tty->write_lock, flags);



	gb_tty->close_pending = false;

}



static const struct tty_operations gb_ops = {

	.install =		gb_tty_install,

	.open =			gb_tty_open,
@@ -641,6 +717,7 @@ static const struct tty_operations gb_ops = { 


static struct tty_port_operations gb_port_ops = {

	.dtr_rts =		gb_tty_dtr_rts,

	.shutdown =		gb_tty_port_shutdown,

};



static int gb_uart_probe(struct gbphy_device *gbphy_dev,
@@ -680,6 +757,13 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev, 
		goto exit_connection_destroy;

	}



	INIT_WORK(&gb_tty->tx_work, gb_uart_tx_write_work);



	retval = kfifo_alloc(&gb_tty->write_fifo, GB_UART_WRITE_FIFO_SIZE,

				GFP_KERNEL);

	if (retval)

		goto exit_buf_free;



	minor = alloc_minor(gb_tty);

	if (minor < 0) {

		if (minor == -ENOSPC) {
@@ -689,7 +773,7 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev, 
		} else {

			retval = minor;

		}

		goto exit_buf_free;

		goto exit_kfifo_free;

	}



	gb_tty->minor = minor;
@@ -741,6 +825,8 @@ exit_connection_disable: 
	gb_connection_disable(connection);

exit_release_minor:

	release_minor(gb_tty);

exit_kfifo_free:

	kfifo_free(&gb_tty->write_fifo);

exit_buf_free:

	kfree(gb_tty->buffer);

exit_connection_destroy:
@@ -777,6 +863,7 @@ static void gb_uart_remove(struct gbphy_device *gbphy_dev) 
	gb_connection_disable(connection);

	tty_port_destroy(&gb_tty->port);

	gb_connection_destroy(connection);

	kfifo_free(&gb_tty->write_fifo);

	kfree(gb_tty->buffer);

	kfree(gb_tty);

}

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