Re: [PATCH V3 2/2] tty: serial: uartps: Add rs485 support to uartps driver

From: m . brock
Date: Sat Nov 04 2023 - 11:47:26 EST

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Manikanta Guntupalli wrote on 2023-10-24 16:48:

@@ -193,6 +196,7 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255");
* @clk_rate_change_nb: Notifier block for clock changes
* @quirks: Flags for RXBS support.
* @cts_override: Modem control state override
+ * @gpiod: Pointer to the gpio descriptor

Change gpiod to gpiod_rts maybe?
Later someone might want to use a gpio for cts/dtr/dsr/dcd/ri as well.

*/
struct cdns_uart {
struct uart_port *port;
@@ -203,10 +207,19 @@ struct cdns_uart {
struct notifier_block clk_rate_change_nb;
u32 quirks;
bool cts_override;
+ struct gpio_desc *gpiod;
};
struct cdns_platform_data {
u32 quirks;
};
+
+struct serial_rs485 cdns_rs485_supported = {
+ .flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND |
+ SER_RS485_RTS_AFTER_SEND,
+ .delay_rts_before_send = 1,
+ .delay_rts_after_send = 1,
+};
+
#define to_cdns_uart(_nb) container_of(_nb, struct cdns_uart, \
clk_rate_change_nb)

@@ -305,6 +318,79 @@ static void cdns_uart_handle_rx(void *dev_id,
unsigned int isrstatus)
tty_flip_buffer_push(&port->state->port);
}

+/**
+ * cdns_rs485_config_gpio_rts_high - Configure GPIO/RTS to high
+ * @cdns_uart: Handle to the cdns_uart
+ */
+static void cdns_rs485_config_gpio_rts_high(struct cdns_uart *cdns_uart)
+{
+ u32 val;
+
+ if (cdns_uart->gpiod) {
+ gpiod_set_value(cdns_uart->gpiod, 1);
+ } else {
+ val = readl(cdns_uart->port->membase + CDNS_UART_MODEMCR);
+ val &= ~CDNS_UART_MODEMCR_RTS;
+ writel(val, cdns_uart->port->membase + CDNS_UART_MODEMCR);
+ }
+}
+
+/**
+ * cdns_rs485_config_gpio_rts_low - Configure GPIO/RTS to low
+ * @cdns_uart: Handle to the cdns_uart
+ */
+static void cdns_rs485_config_gpio_rts_low(struct cdns_uart *cdns_uart)
+{
+ u32 val;
+
+ if (cdns_uart->gpiod) {
+ gpiod_set_value(cdns_uart->gpiod, 0);
+ } else {
+ val = readl(cdns_uart->port->membase + CDNS_UART_MODEMCR);
+ val |= CDNS_UART_MODEMCR_RTS;
+ writel(val, cdns_uart->port->membase + CDNS_UART_MODEMCR);
+ }
+}
+
+/**
+ * cdns_rs485_tx_setup - Tx setup specific to rs485
+ * @cdns_uart: Handle to the cdns_uart
+ */
+static void cdns_rs485_tx_setup(struct cdns_uart *cdns_uart)
+{
+ if (cdns_uart->port->rs485.flags & SER_RS485_RTS_ON_SEND)
+ cdns_rs485_config_gpio_rts_high(cdns_uart);
+ else
+ cdns_rs485_config_gpio_rts_low(cdns_uart);
+}
+
+/**
+ * cdns_rs485_rx_setup - Rx setup specific to rs485
+ * @cdns_uart: Handle to the cdns_uart
+ */
+static void cdns_rs485_rx_setup(struct cdns_uart *cdns_uart)
+{
+ if (cdns_uart->port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
+ cdns_rs485_config_gpio_rts_high(cdns_uart);
+ else
+ cdns_rs485_config_gpio_rts_low(cdns_uart);
+}

Why not simply create:
void cdns_rs485_driver_enable(struct cdns_uart *cdns_uart, bool enable)

And let it handle the rs485.flags itself?

+
+/**
+ * cdns_uart_tx_empty - Check whether TX is empty
+ * @port: Handle to the uart port structure
+ *
+ * Return: TIOCSER_TEMT on success, 0 otherwise
+ */
+static unsigned int cdns_uart_tx_empty(struct uart_port *port)
+{
+ unsigned int status;
+
+ status = readl(port->membase + CDNS_UART_SR) &
+ (CDNS_UART_SR_TXEMPTY | CDNS_UART_SR_TACTIVE);
+ return (status == CDNS_UART_SR_TXEMPTY) ? TIOCSER_TEMT : 0;
+}
+
/**
* cdns_uart_handle_tx - Handle the bytes to be Txed.
* @dev_id: Id of the UART port
@@ -571,6 +657,8 @@ static int cdns_uart_clk_notifier_cb(struct
notifier_block *nb,
static void cdns_uart_start_tx(struct uart_port *port)
{
unsigned int status;
+ unsigned long time_out;
+ struct cdns_uart *cdns_uart = port->private_data;

if (uart_tx_stopped(port))
return;
@@ -589,8 +677,31 @@ static void cdns_uart_start_tx(struct uart_port *port)

writel(CDNS_UART_IXR_TXEMPTY, port->membase + CDNS_UART_ISR);
+ if (cdns_uart->port->rs485.flags & SER_RS485_ENABLED) {
+ cdns_rs485_tx_setup(cdns_uart);
+ if (cdns_uart->port->rs485.delay_rts_before_send)
+ mdelay(cdns_uart->port->rs485.delay_rts_before_send);

Would it not be better to start a timer here with a callback that enables
the TXEMPTY interrupt? That would automatically call cdns_uart_handle_tx().

+ }
+
cdns_uart_handle_tx(port);

+ if (cdns_uart->port->rs485.flags & SER_RS485_ENABLED) {
+ time_out = jiffies + usecs_to_jiffies(TX_TIMEOUT);
+ /* Wait for tx completion */
+ while ((cdns_uart_tx_empty(cdns_uart->port) != TIOCSER_TEMT) &&
+ time_before(jiffies, time_out))
+ cpu_relax();
+
+ if (cdns_uart->port->rs485.delay_rts_after_send)
+ mdelay(cdns_uart->port->rs485.delay_rts_after_send);
+
+ /*
+ * Default Rx should be setup, because RX signaling path
+ * need to enable to receive data.
+ */
+ cdns_rs485_rx_setup(cdns_uart);
+ }

I think this should be done from the TXEMPTY interrupt. And again schedule a
timer to drop the DE line. You really can do this without using mdelay().

+
/* Enable the TX Empty interrupt */
writel(CDNS_UART_IXR_TXEMPTY, port->membase + CDNS_UART_IER);
}
@@ -602,6 +713,14 @@ static void cdns_uart_start_tx(struct uart_port *port)
static void cdns_uart_stop_tx(struct uart_port *port)
{
unsigned int regval;
+ struct cdns_uart *cdns_uart = port->private_data;
+
+ if (cdns_uart->port->rs485.flags & SER_RS485_ENABLED) {
+ if (cdns_uart->port->rs485.delay_rts_after_send)
+ mdelay(cdns_uart->port->rs485.delay_rts_after_send);
+
+ cdns_rs485_rx_setup(cdns_uart);
+ }

Again, start a timer and wait for completion?

regval = readl(port->membase + CDNS_UART_CR);
regval |= CDNS_UART_CR_TX_DIS;
@@ -626,21 +745,6 @@ static void cdns_uart_stop_rx(struct uart_port *port)
writel(regval, port->membase + CDNS_UART_CR);
}

-/**
- * cdns_uart_tx_empty - Check whether TX is empty
- * @port: Handle to the uart port structure
- *
- * Return: TIOCSER_TEMT on success, 0 otherwise
- */
-static unsigned int cdns_uart_tx_empty(struct uart_port *port)
-{
- unsigned int status;
-
- status = readl(port->membase + CDNS_UART_SR) &
- (CDNS_UART_SR_TXEMPTY | CDNS_UART_SR_TACTIVE);
- return (status == CDNS_UART_SR_TXEMPTY) ? TIOCSER_TEMT : 0;
-}
-
/**
* cdns_uart_break_ctl - Based on the input ctl we have to start or stop
* transmitting char breaks
@@ -829,6 +933,9 @@ static int cdns_uart_startup(struct uart_port *port)
(CDNS_UART_CR_TXRST | CDNS_UART_CR_RXRST))
cpu_relax();

+ if (cdns_uart->port->rs485.flags & SER_RS485_ENABLED)
+ cdns_rs485_rx_setup(cdns_uart);
+
/*
* Clear the RX disable bit and then set the RX enable bit to enable
* the receiver.
@@ -1455,6 +1562,23 @@ MODULE_DEVICE_TABLE(of, cdns_uart_of_match);
/* Temporary variable for storing number of instances */
static int instances;

+/**
+ * cdns_rs485_config - Called when an application calls TIOCSRS485 ioctl.
+ * @port: Pointer to the uart_port structure
+ * @termios: Pointer to the ktermios structure
+ * @rs485: Pointer to the serial_rs485 structure
+ *
+ * Return: 0
+ */
+static int cdns_rs485_config(struct uart_port *port, struct ktermios *termios,
+ struct serial_rs485 *rs485)
+{
+ if (rs485->flags & SER_RS485_ENABLED)
+ dev_dbg(port->dev, "Setting UART to RS485\n");
+

Shouldn't you force automatic RTS control off here?
And also call cdns_rs485_rx_setup()

+ return 0;
+}
+
/**
* cdns_uart_probe - Platform driver probe
* @pdev: Pointer to the platform device structure
@@ -1463,6 +1587,7 @@ static int instances;
*/
static int cdns_uart_probe(struct platform_device *pdev)
{
+ u32 val;
int rc, id, irq;
struct uart_port *port;
struct resource *res;
@@ -1597,9 +1722,23 @@ static int cdns_uart_probe(struct platform_device *pdev)
port->private_data = cdns_uart_data;
port->read_status_mask = CDNS_UART_IXR_TXEMPTY | CDNS_UART_IXR_RXTRIG |
CDNS_UART_IXR_OVERRUN | CDNS_UART_IXR_TOUT;
+ port->rs485_config = cdns_rs485_config;
+ port->rs485_supported = cdns_rs485_supported;
cdns_uart_data->port = port;
platform_set_drvdata(pdev, port);

+ rc = uart_get_rs485_mode(port);
+ if (rc)
+ goto err_out_clk_notifier;
+
+ cdns_uart_data->gpiod = devm_gpiod_get_optional(&pdev->dev, "rts",
+ GPIOD_OUT_LOW);
+ if (IS_ERR(cdns_uart_data->gpiod)) {
+ rc = PTR_ERR(cdns_uart_data->gpiod);
+ dev_err(port->dev, "xuartps: devm_gpiod_get_optional failed\n");
+ goto err_out_clk_notifier;
+ }
+
pm_runtime_use_autosuspend(&pdev->dev);
pm_runtime_set_autosuspend_delay(&pdev->dev, UART_AUTOSUSPEND_TIMEOUT);
pm_runtime_set_active(&pdev->dev);
@@ -1638,6 +1777,16 @@ static int cdns_uart_probe(struct platform_device *pdev)
cdns_uart_data->cts_override = of_property_read_bool(pdev->dev.of_node,
"cts-override");

+ if (cdns_uart_data->port->rs485.flags & SER_RS485_ENABLED) {
+ if (!cdns_uart_data->gpiod) {
+ val = readl(cdns_uart_data->port->membase
+ + CDNS_UART_MODEMCR);
+ val |= CDNS_UART_MODEMCR_RTS;
+ writel(val, cdns_uart_data->port->membase
+ + CDNS_UART_MODEMCR);
+ }
+ }

Simply call cdns_rs485_rx_setup() ?

+
instances++;

return 0;
@@ -1646,6 +1795,7 @@ static int cdns_uart_probe(struct platform_device *pdev)
pm_runtime_disable(&pdev->dev);
pm_runtime_set_suspended(&pdev->dev);
pm_runtime_dont_use_autosuspend(&pdev->dev);
+err_out_clk_notifier:
#ifdef CONFIG_COMMON_CLK
clk_notifier_unregister(cdns_uart_data->uartclk,
&cdns_uart_data->clk_rate_change_nb);

Please also modify cdns_uart_[s|g]et_mctrl() so they support rts-gpios.

Maarten

Next message: Armin Wolf: "[PATCH v2 1/9] hwmon: (dell-smm) Prepare for multiple SMM calling backends"
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