Provide an interface to 8250 driver to set DMA mode. It will be effective
for the transfers through the port next time it will be opened.
TBD: sysfs ABI documentation
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-tty | 11 ++++
drivers/tty/serial/8250/8250_port.c | 110 +++++++++++++++++++++++++++++++++++-
2 files changed, 119 insertions(+), 2 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-tty b/Documentation/ABI/testing/sysfs-tty
index 9eb3c2b..1dd68c9 100644
--- a/Documentation/ABI/testing/sysfs-tty
+++ b/Documentation/ABI/testing/sysfs-tty
@@ -154,3 +154,14 @@ Description:
device specification. For example, when user sets 7bytes on
16550A, which has 1/4/8/14 bytes trigger, the RX trigger is
automatically changed to 4 bytes.
+
+What: /sys/class/tty/ttyS0/skip_rxdma
+What: /sys/class/tty/ttyS0/skip_txdma
+Date: September 2016
+Contact: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
+Description:
+ Shows the current state of DMA use per channel or enforces PIO
+ mode. Users can show this value regardless of opening the
+ serial device file or not, though setting change is allowed
+ only on closed device. The change will be effective as of next
+ port opening.
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index a00f2c3..14bfd7b 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2904,14 +2904,120 @@ static DEVICE_ATTR(rx_trig_bytes, S_IRUSR | S_IWUSR | S_IRGRP,
serial8250_get_attr_rx_trig_bytes,
serial8250_set_attr_rx_trig_bytes);
+static ssize_t serial8250_get_attr_skip_rxdma(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct tty_port *port = dev_get_drvdata(dev);
+ struct uart_state *state = container_of(port, struct uart_state, port);
+ struct uart_port *uport = state->uart_port;
+ bool skip_rxdma;
+
+ mutex_lock(&port->mutex);
+ skip_rxdma = !!(uport->quirks & UPQ_NO_DMA_RX);
+ mutex_unlock(&port->mutex);
+
+ return snprintf(buf, PAGE_SIZE, "%c\n", skip_rxdma ? 'Y' : 'N');
+}
+
+static ssize_t serial8250_set_attr_skip_rxdma(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct tty_port *port = dev_get_drvdata(dev);
+ struct uart_state *state = container_of(port, struct uart_state, port);
+ struct uart_port *uport = state->uart_port;
+ struct uart_8250_port *up = up_to_u8250p(uport);
+ bool skip_rxdma;
+ int ret;
+
+ if (!up->dma)
+ return -ENODEV;
+
+ ret = kstrtobool(buf, &skip_rxdma);
+ if (ret < 0)
+ return ret;
+
+ mutex_lock(&port->mutex);
+ if (up->dma->in_use)
+ count = -EBUSY;
+ else {
+ if (skip_rxdma)
+ uport->quirks |= UPQ_NO_DMA_RX;
+ else
+ uport->quirks &= ~UPQ_NO_DMA_RX;
+ }
+ mutex_unlock(&port->mutex);
+
+ return count;
+}
+
+static DEVICE_ATTR(skip_rxdma, S_IRUSR | S_IWUSR | S_IRGRP,
+ serial8250_get_attr_skip_rxdma,
+ serial8250_set_attr_skip_rxdma);
+
+static ssize_t serial8250_get_attr_skip_txdma(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct tty_port *port = dev_get_drvdata(dev);
+ struct uart_state *state = container_of(port, struct uart_state, port);
+ struct uart_port *uport = state->uart_port;
+ bool skip_txdma;
+
+ mutex_lock(&port->mutex);
+ skip_txdma = !!(uport->quirks & UPQ_NO_DMA_TX);
+ mutex_unlock(&port->mutex);
+
+ return snprintf(buf, PAGE_SIZE, "%c\n", skip_txdma ? 'Y' : 'N');
+}
+
+static ssize_t serial8250_set_attr_skip_txdma(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct tty_port *port = dev_get_drvdata(dev);
+ struct uart_state *state = container_of(port, struct uart_state, port);
+ struct uart_port *uport = state->uart_port;
+ struct uart_8250_port *up = up_to_u8250p(uport);
+ bool skip_txdma;
+ int ret;
+
+ if (!up->dma)
+ return -ENODEV;
+
+ ret = kstrtobool(buf, &skip_txdma);
+ if (ret < 0)
+ return ret;
+
+ mutex_lock(&port->mutex);
+ if (up->dma->in_use)
+ count = -EBUSY;
+ else {
+ if (skip_txdma)
+ uport->quirks |= UPQ_NO_DMA_TX;
+ else
+ uport->quirks &= ~UPQ_NO_DMA_TX;
+ }
+ mutex_unlock(&port->mutex);
+
+ return count;
+}
+
+static DEVICE_ATTR(skip_txdma, S_IRUSR | S_IWUSR | S_IRGRP,
+ serial8250_get_attr_skip_txdma,
+ serial8250_set_attr_skip_txdma);
+
static struct attribute *serial8250_dev_attrs[] = {
&dev_attr_rx_trig_bytes.attr,
+ &dev_attr_skip_rxdma.attr,
+ &dev_attr_skip_txdma.attr,
NULL,
- };
+};
static struct attribute_group serial8250_dev_attr_group = {
.attrs = serial8250_dev_attrs,
- };
+};
static void register_dev_spec_attr_grp(struct uart_8250_port *up)
{
--
2.9.3
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