In order to optimize serial communication on imx53 and imx6, we may
need to tweak DMA period and buffer length per period.
This patch add sysfs attributes to configure thoses values before
initialising DMA.
For example, you can access values by reading/writing:
/sys/class/tty/ttymxc*/dma_buffer_size
/sys/class/tty/ttymxc*/dma_buffer_count
Changes since v1:
- use uart_port attr_group field instead of using sysfs_create_file.
- remove useless mutex
- Fix typo
- Document sysfs attributes
- Change attributes name
Signed-off-by: Fabien Lahoudere <fabien.lahoudere@xxxxxxxxxxxxx>
---
Documentation/ABI/stable/sysfs-driver-imx-uart | 10 +++
drivers/tty/serial/imx.c | 94 ++++++++++++++++++++++++--
2 files changed, 99 insertions(+), 5 deletions(-)
create mode 100644 Documentation/ABI/stable/sysfs-driver-imx-uart
diff --git a/Documentation/ABI/stable/sysfs-driver-imx-uart b/Documentation/ABI/stable/sysfs-driver-imx-uart
new file mode 100644
index 0000000..0ec9ee2
--- /dev/null
+++ b/Documentation/ABI/stable/sysfs-driver-imx-uart
@@ -0,0 +1,10 @@
+What: /sys/class/tty/ttymxc*/dma_buffer_count
+Date: July 2018
+Contact: Fabien Lahoudere <fabien.lahoudere@xxxxxxxxxxxxx>
+Description: This attribute handles field rx_periods in struct imx_uart.
+
+What: /sys/class/tty/ttymxc*/dma_buffer_size
+Date: July 2018
+Contact: Fabien Lahoudere <fabien.lahoudere@xxxxxxxxxxxxx>
+Description: This attribute handles field rx_period_length in struct imx_uart.
+
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 4e85357..726f644 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -218,7 +218,9 @@ struct imx_port {
struct dma_chan *dma_chan_rx, *dma_chan_tx;
struct scatterlist rx_sgl, tx_sgl[2];
void *rx_buf;
+ unsigned int rx_buf_size;
struct circ_buf rx_ring;
+ unsigned int rx_period_length;
unsigned int rx_periods;
dma_cookie_t rx_cookie;
unsigned int tx_bytes;
@@ -1028,8 +1030,6 @@ static void imx_uart_timeout(struct timer_list *t)
}
}
-#define RX_BUF_SIZE (PAGE_SIZE)
-
/*
* There are two kinds of RX DMA interrupts(such as in the MX6Q):
* [1] the RX DMA buffer is full.
@@ -1124,9 +1124,8 @@ static int imx_uart_start_rx_dma(struct imx_port *sport)
sport->rx_ring.head = 0;
sport->rx_ring.tail = 0;
- sport->rx_periods = RX_DMA_PERIODS;
- sg_init_one(sgl, sport->rx_buf, RX_BUF_SIZE);
+ sg_init_one(sgl, sport->rx_buf, sport->rx_buf_size);
ret = dma_map_sg(dev, sgl, 1, DMA_FROM_DEVICE);
if (ret == 0) {
dev_err(dev, "DMA mapping error for RX.\n");
@@ -1244,7 +1243,8 @@ static int imx_uart_dma_init(struct imx_port *sport)
goto err;
}
- sport->rx_buf = kzalloc(RX_BUF_SIZE, GFP_KERNEL);
+ sport->rx_buf_size = sport->rx_period_length * sport->rx_periods;
+ sport->rx_buf = kzalloc(sport->rx_buf_size, GFP_KERNEL);
if (!sport->rx_buf) {
ret = -ENOMEM;
goto err;
@@ -1705,6 +1705,87 @@ static const char *imx_uart_type(struct uart_port *port)
return sport->port.type == PORT_IMX ? "IMX" : NULL;
}
+
+static ssize_t dma_buffer_size_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned int plen;
+ int ret;
+ struct device *port_device = dev->parent;
+ struct imx_port *sport = dev_get_drvdata(port_device);
+
+ if (sport->dma_chan_rx) {
+ dev_warn(dev,
+ "You cannot set dma buffer size if DMA is inited\n");
+ return -EBUSY;
+ }
+ ret = kstrtou32(buf, 0, &plen);
+ if (ret < 0)
+ dev_warn(dev, "Bad argument %s\n", buf);
+ else {
+ sport->rx_period_length = plen;
+ ret = count;
+ }
+ return ret;
+}
+
+static ssize_t dma_buffer_size_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct device *port_device = dev->parent;
+ struct imx_port *sport = dev_get_drvdata(port_device);
+
+ return snprintf(buf, PAGE_SIZE, "%u\n", sport->rx_period_length);
+}
+
+static ssize_t dma_buffer_count_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned int periods;
+ int ret;
+ struct device *port_device = dev->parent;
+ struct imx_port *sport = dev_get_drvdata(port_device);
+
+ if (sport->dma_chan_rx) {
+ dev_warn(dev,
+ "You cannot set dma buffer count if DMA is inited\n");
+ return -EBUSY;
+ }
+ ret = kstrtou32(buf, 0, &periods);
+ if (ret < 0)
+ dev_warn(dev, "Bad argument %s\n", buf);
+ else {
+ sport->rx_periods = periods;
+ ret = count;
+ }
+ return ret;
+}
+
+static ssize_t dma_buffer_count_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct device *port_device = dev->parent;
+ struct imx_port *sport = dev_get_drvdata(port_device);
+
+ return snprintf(buf, PAGE_SIZE, "%u\n", sport->rx_periods);
+}
+
+static DEVICE_ATTR_RW(dma_buffer_size);
+static DEVICE_ATTR_RW(dma_buffer_count);
+
+static struct attribute *imx_uart_attrs[] = {
+ &dev_attr_dma_buffer_size.attr,
+ &dev_attr_dma_buffer_count.attr,
+ NULL,
+};
+static struct attribute_group imx_uart_attr_group = {
+ .attrs = imx_uart_attrs,
+};
+
/*
* Configure/autoconfigure the port.
*/
@@ -2236,6 +2317,9 @@ static int imx_uart_probe(struct platform_device *pdev)
sport->port.rs485_config = imx_uart_rs485_config;
sport->port.flags = UPF_BOOT_AUTOCONF;
timer_setup(&sport->timer, imx_uart_timeout, 0);
+ sport->rx_period_length = PAGE_SIZE / RX_DMA_PERIODS;
+ sport->rx_periods = RX_DMA_PERIODS;
+ sport->port.attr_group = &imx_uart_attr_group;
sport->gpios = mctrl_gpio_init(&sport->port, 0);
if (IS_ERR(sport->gpios))
--
1.8.3.1
--
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