console: Add simplified 'serdev' framework from Linux kernel

Port 'serdev' UART-slave deivce framework found in recent Linux
kernels (post 4.13) in order to be able to port 'serdev' slave drivers
from Linux.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 89 insertions, 0 deletions

diff --git a/common/serdev.c b/common/serdev.c
new file mode 100644
index 0000000000..32743738ed
--- /dev/null
+++ b/common/serdev.c
@@ -0,0 +1,89 @@
+
+#include <common.h>
+#include <serdev.h>
+
+static void serdev_device_poller(void *context)
+{
+	struct serdev_device *serdev = context;
+	struct console_device *cdev = to_console_device(serdev);
+	unsigned char *buf = serdev->buf;
+	int ret, len;
+
+	/*
+	 * Since this callback is a part of poller infrastructure we
+	 * want to use _non_interruptible version of the function
+	 * below to prevent recursion from happening (regular
+	 * console_drain will call is_timeout, which might end up
+	 * calling this function again).
+	 */
+	len = console_drain_non_interruptible(cdev, serdev->fifo, buf,
+					      PAGE_SIZE,
+					      serdev->polling_window);
+	while (len > 0) {
+		ret = serdev->receive_buf(serdev, buf, len);
+		len -= ret;
+		buf += ret;
+	}
+
+	if (serdev->polling_interval) {
+		/*
+		 * Re-schedule ourselves in 'serdev->polling_interval'
+		 * nanoseconds
+		 */
+		poller_call_async(&serdev->poller,
+				  serdev->polling_interval,
+				  serdev_device_poller,
+				  serdev);
+	}
+}
+
+int serdev_device_open(struct serdev_device *serdev)
+{
+	struct console_device *cdev = to_console_device(serdev);
+	int ret;
+
+	if (!cdev->putc || !cdev->getc)
+		return -EINVAL;
+
+	if (!serdev->polling_window)
+		return -EINVAL;
+
+	serdev->buf = xzalloc(PAGE_SIZE);
+	serdev->fifo = kfifo_alloc(PAGE_SIZE);
+	if (!serdev->fifo)
+		return -ENOMEM;
+
+	ret = poller_async_register(&serdev->poller);
+	if (ret)
+		return ret;
+
+	return console_open(cdev);
+}
+
+unsigned int serdev_device_set_baudrate(struct serdev_device *serdev,
+					unsigned int speed)
+{
+	struct console_device *cdev = to_console_device(serdev);
+
+	if (console_set_baudrate(cdev, speed) < 0)
+		return 0;
+
+	return console_get_baudrate(cdev);
+}
+
+int serdev_device_write(struct serdev_device *serdev, const unsigned char *buf,
+			size_t count, unsigned long timeout)
+{
+	struct console_device *cdev = to_console_device(serdev);
+
+	while (count--)
+		cdev->putc(cdev, *buf++);
+	/*
+	 * Poll Rx once right after we just send some data in case our
+	 * serdev device implements command/response type of a
+	 * protocol and we need to start draining input as soon as
+	 * possible.
+	 */
+	serdev_device_poller(serdev);
+	return 0;
+}