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Message-ID: <20251130104222.63077-32-crescentcy.hsieh@moxa.com>
Date: Sun, 30 Nov 2025 18:42:22 +0800
From: Crescent Hsieh <crescentcy.hsieh@...a.com>
To: gregkh@...uxfoundation.org,
jirislaby@...nel.org,
ilpo.jarvinen@...ux.intel.com,
andy.shevchenko@...il.com
Cc: linux-kernel@...r.kernel.org,
linux-serial@...r.kernel.org,
crescentcy.hsieh@...a.com
Subject: [PATCH v1 31/31] serial: 8250_mxpcie: add RS485-2W auto-adjust sysfs control
Moxa CP118E/CP138E/CP134EL/CP116E boards support a hardware "auto mode"
in RS485-2W where the CPLD can automatically configure terminator and
pull-state based on the selected baud rate and line condition. This mode
is not meant to be kept enabled continuously — instead, it is triggered
for a short period (about 2s) to let the hardware calibrate itself.
This patch adds a write-only sysfs attribute that requests a one-shot
hardware auto-adjust of terminator and pull-state. Writing a supported
baud rate value (one of 9600, 19200, 38400, 57600, 115200, 230400,
460800, or 921600) into the attribute programs the CPLD baud code and
runs a temporary AUTO mode cycle (about 2s) on RS485-2W ports of the
supported boards. Invalid interfaces or devices are rejected.
Signed-off-by: Crescent Hsieh <crescentcy.hsieh@...a.com>
---
drivers/tty/serial/8250/8250_mxpcie.c | 143 ++++++++++++++++++++++++++
1 file changed, 143 insertions(+)
diff --git a/drivers/tty/serial/8250/8250_mxpcie.c b/drivers/tty/serial/8250/8250_mxpcie.c
index e9e3d03b7712..b3146cac0298 100644
--- a/drivers/tty/serial/8250/8250_mxpcie.c
+++ b/drivers/tty/serial/8250/8250_mxpcie.c
@@ -107,11 +107,15 @@
#define MOXA_CPLD_SET_STATE_BASE 0x18
#define MOXA_CPLD_STATE_MASK 0x0F
+#define MOXA_CPLD_SET_BAUD_BASE 0x08
+#define MOXA_CPLD_BAUD_MASK 0x07
+
#define MOXA_CPLD_DATA_MASK 0x1F /* Pin0 ~ Pin4 */
#define MOXA_CPLD_CTRL_MASK 0xE0 /* Pin5 ~ Pin7 */
#define MOXA_CPLD_PULL_STATE_FLAG 0x01
#define MOXA_CPLD_TERMINATOR_FLAG 0x02
+#define MOXA_CPLD_AUTO_MODE_FLAG 0x08
#define MOXA_CPLD_READ 0
#define MOXA_CPLD_WRITE 1
@@ -125,6 +129,18 @@
#define MOXA_PULL_STATE_ENABLE 1
#define MOXA_PULL_STATE_DISABLE 0
+#define MOXA_AUTO_MODE_ENABLE 1
+#define MOXA_AUTO_MODE_DISABLE 0
+
+#define MOXA_CPLD_BAUD_9600 0
+#define MOXA_CPLD_BAUD_19200 1
+#define MOXA_CPLD_BAUD_38400 2
+#define MOXA_CPLD_BAUD_57600 3
+#define MOXA_CPLD_BAUD_115200 4
+#define MOXA_CPLD_BAUD_230400 5
+#define MOXA_CPLD_BAUD_460800 6
+#define MOXA_CPLD_BAUD_921600 7
+
#define MOXA_UIR_OFFSET 0x04
#define MOXA_UIR_RS232 0x00
#define MOXA_UIR_RS422 0x01
@@ -566,6 +582,54 @@ static int mxpcie8250_cpld_get_pull_state(resource_size_t iobar_addr, u8 port_id
return MOXA_PULL_STATE_DISABLE;
}
+/**
+ * mxpcie8250_cpld_set_auto_mode() - Set the auto mode of the specified port
+ * @iobar_addr: The base address of the GPIO I/O region
+ * @port_idx: The port index (0 to 7)
+ * @state: Desired auto mode state (MOXA_AUTO_MODE_ENABLE or MOXA_AUTO_MODE_DISABLE)
+ *
+ * Updates the auto mode setting in the CPLD for the specified port by reading
+ * the current state, modifying the auto mode bit, and writing the updated
+ * state back to the CPLD.
+ */
+static void mxpcie8250_cpld_set_auto_mode(resource_size_t iobar_addr, u8 port_idx, u8 state)
+{
+ u8 addr, data;
+
+ addr = MOXA_CPLD_GET_STATE_BASE + port_idx;
+ mxpcie8250_cpld_read(iobar_addr, addr, &data);
+
+ data = data & MOXA_CPLD_STATE_MASK;
+
+ if (state == MOXA_AUTO_MODE_ENABLE)
+ data |= MOXA_CPLD_AUTO_MODE_FLAG;
+ else
+ data &= ~MOXA_CPLD_AUTO_MODE_FLAG;
+
+ addr = MOXA_CPLD_SET_STATE_BASE + port_idx;
+ mxpcie8250_cpld_write(iobar_addr, addr, data);
+}
+
+/**
+ * mxpcie8250_cpld_set_baud_rate() - Set the baud rate code of the specified port
+ * @iobar_addr: The base address of the GPIO I/O region
+ * @port_idx: The port index (0 to 7)
+ * @baud: CPLD baud rate code (MOXA_CPLD_BAUD_9600 ... MOXA_CPLD_BAUD_921600)
+ *
+ * Writes the baud rate selection value directly into the CPLD SET_BAUD register
+ * for the specified port. The caller must ensure the value is pre-mapped to
+ * the 3-bit CPLD baud code.
+ */
+static void mxpcie8250_cpld_set_baud_rate(resource_size_t iobar_addr, u8 port_idx, u8 baud)
+{
+ u8 addr, data;
+
+ data = baud & MOXA_CPLD_BAUD_MASK;
+
+ addr = MOXA_CPLD_SET_BAUD_BASE + port_idx;
+ mxpcie8250_cpld_write(iobar_addr, addr, data);
+}
+
static bool mxpcie8250_is_mini_pcie(unsigned short device)
{
if (device == PCI_DEVICE_ID_MOXA_CP102N ||
@@ -1134,12 +1198,91 @@ static ssize_t mxpcie8250_pull_state_show(struct device *dev,
return -ENODEV;
}
+static ssize_t mxpcie8250_auto_mode_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf,
+ size_t count)
+{
+ struct tty_port *tport = dev_get_drvdata(dev);
+ struct uart_state *ustate = container_of(tport, struct uart_state, port);
+ struct uart_port *port = ustate->uart_port;
+ struct pci_dev *pdev = to_pci_dev(port->dev);
+ struct mxpcie8250 *priv = pci_get_drvdata(pdev);
+ resource_size_t iobar_addr = pci_resource_start(pdev, 2);
+ int ret;
+ u32 baud;
+
+ if (!count)
+ return -EINVAL;
+
+ ret = kstrtou32(buf, 10, &baud);
+
+ if (ret < 0)
+ return ret;
+
+ if (priv->port[port->port_id].interface != MOXA_UIR_RS485_2W) {
+ dev_warn(dev, "The serial interface of this port should be RS485-2W\n");
+ return -EINVAL;
+ }
+ if (pdev->device == PCI_DEVICE_ID_MOXA_CP118E_A_I ||
+ pdev->device == PCI_DEVICE_ID_MOXA_CP138E_A ||
+ pdev->device == PCI_DEVICE_ID_MOXA_CP134EL_A ||
+ pdev->device == PCI_DEVICE_ID_MOXA_CP116E_A_A ||
+ pdev->device == PCI_DEVICE_ID_MOXA_CP116E_A_B) {
+ switch (baud) {
+ case 9600:
+ baud = MOXA_CPLD_BAUD_9600;
+ break;
+ case 19200:
+ baud = MOXA_CPLD_BAUD_19200;
+ break;
+ case 38400:
+ baud = MOXA_CPLD_BAUD_38400;
+ break;
+ case 57600:
+ baud = MOXA_CPLD_BAUD_57600;
+ break;
+ case 115200:
+ baud = MOXA_CPLD_BAUD_115200;
+ break;
+ case 230400:
+ baud = MOXA_CPLD_BAUD_230400;
+ break;
+ case 460800:
+ baud = MOXA_CPLD_BAUD_460800;
+ break;
+ case 921600:
+ baud = MOXA_CPLD_BAUD_921600;
+ break;
+ default:
+ dev_warn(dev, "The baud rate should be one of 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600\n");
+ return -EINVAL;
+ }
+ spin_lock(&priv->board_lock);
+ mxpcie8250_cpld_set_baud_rate(iobar_addr, port->port_id, baud);
+ mxpcie8250_cpld_set_auto_mode(iobar_addr, port->port_id, MOXA_AUTO_MODE_ENABLE);
+ spin_unlock(&priv->board_lock);
+
+ msleep(2000);
+
+ spin_lock(&priv->board_lock);
+ mxpcie8250_cpld_set_auto_mode(iobar_addr, port->port_id, MOXA_AUTO_MODE_DISABLE);
+ spin_unlock(&priv->board_lock);
+
+ return count;
+ }
+
+ return -ENODEV;
+}
+
static DEVICE_ATTR_RW(mxpcie8250_terminator);
static DEVICE_ATTR_RW(mxpcie8250_pull_state);
+static DEVICE_ATTR_WO(mxpcie8250_auto_mode);
static struct attribute *mxpcie8250_dev_attrs[] = {
&dev_attr_mxpcie8250_terminator.attr,
&dev_attr_mxpcie8250_pull_state.attr,
+ &dev_attr_mxpcie8250_auto_mode.attr,
NULL
};
--
2.45.2
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