[v7,tty-next,3/4] serial: 8250_pci1xxxx: Add RS485 support to quad-uart driver
Commit Message
pci1xxxx uart supports RS485 mode of operation in the hardware with
auto-direction control with configurable delay for releasing RTS after
the transmission. This patch adds support for the RS485 mode.
Co-developed-by: Tharun Kumar P <tharunkumar.pasumarthi@microchip.com>
Signed-off-by: Tharun Kumar P <tharunkumar.pasumarthi@microchip.com>
Signed-off-by: Kumaravel Thiagarajan <kumaravel.thiagarajan@microchip.com>
---
Changes in v7:
- No Change
Changes in v6:
- Modified datatype of delay_in_baud_periods to u64 to avoid overflows
Changes in v5:
- Removed unnecessary assignments
- Corrected styling issues in comments
Changes in v4:
- No Change
Changes in v3:
- Remove flags sanitization in driver which is taken care in core
Changes in v2:
- move pci1xxxx_rs485_config to a separate patch with
pci1xxxx_rs485_supported.
---
drivers/tty/serial/8250/8250_pci1xxxx.c | 49 +++++++++++++++++++++++++
1 file changed, 49 insertions(+)
Comments
On Thu, 8 Dec 2022, Kumaravel Thiagarajan wrote:
> pci1xxxx uart supports RS485 mode of operation in the hardware with
> auto-direction control with configurable delay for releasing RTS after
> the transmission. This patch adds support for the RS485 mode.
>
> Co-developed-by: Tharun Kumar P <tharunkumar.pasumarthi@microchip.com>
> Signed-off-by: Tharun Kumar P <tharunkumar.pasumarthi@microchip.com>
> Signed-off-by: Kumaravel Thiagarajan <kumaravel.thiagarajan@microchip.com>
> ---
> Changes in v7:
> - No Change
>
> Changes in v6:
> - Modified datatype of delay_in_baud_periods to u64 to avoid overflows
>
> Changes in v5:
> - Removed unnecessary assignments
> - Corrected styling issues in comments
>
> Changes in v4:
> - No Change
>
> Changes in v3:
> - Remove flags sanitization in driver which is taken care in core
>
> Changes in v2:
> - move pci1xxxx_rs485_config to a separate patch with
> pci1xxxx_rs485_supported.
> ---
> drivers/tty/serial/8250/8250_pci1xxxx.c | 49 +++++++++++++++++++++++++
> 1 file changed, 49 insertions(+)
>
> diff --git a/drivers/tty/serial/8250/8250_pci1xxxx.c b/drivers/tty/serial/8250/8250_pci1xxxx.c
> index be554e2d884b..9f0da264314a 100644
> --- a/drivers/tty/serial/8250/8250_pci1xxxx.c
> +++ b/drivers/tty/serial/8250/8250_pci1xxxx.c
> @@ -145,6 +145,53 @@ static void pci1xxxx_set_divisor(struct uart_port *port, unsigned int baud,
> port->membase + UART_BAUD_CLK_DIVISOR_REG);
> }
>
> +static int pci1xxxx_rs485_config(struct uart_port *port,
> + struct ktermios *termios,
> + struct serial_rs485 *rs485)
> +{
> + u32 clock_div = readl(port->membase + UART_BAUD_CLK_DIVISOR_REG);
> + u64 delay_in_baud_periods;
> + u32 baud_period_in_ns;
> + u32 data = 0;
> +
> + /*
> + * pci1xxxx's uart hardware supports only RTS delay after
> + * Tx and in units of bit times to a maximum of 15
> + */
> + if (rs485->flags & SER_RS485_ENABLED) {
> + data = ADCL_CFG_EN | ADCL_CFG_PIN_SEL;
> +
> + if (!(rs485->flags & SER_RS485_RTS_ON_SEND))
> + data |= ADCL_CFG_POL_SEL;
> +
> + if (rs485->delay_rts_after_send) {
> + baud_period_in_ns =
> + FIELD_GET(BAUD_CLOCK_DIV_INT_MSK, clock_div) *
> + UART_BIT_SAMPLE_CNT;
> + delay_in_baud_periods =
> + rs485->delay_rts_after_send * NSEC_PER_MSEC /
> + baud_period_in_ns;
> + delay_in_baud_periods =
> + min_t(u64, delay_in_baud_periods,
> + FIELD_MAX(ADCL_CFG_RTS_DELAY_MASK));
> + data |= FIELD_PREP(ADCL_CFG_RTS_DELAY_MASK,
> + delay_in_baud_periods);
> + rs485->delay_rts_after_send =
> + baud_period_in_ns * delay_in_baud_periods /
> + NSEC_PER_MSEC;
div_u64() or cast+comment if you can prove you never need the high-word at
this point.
But why you even need u64 because delay_rts_after_send is limited to
RS485_MAX_RTS_DELAY (=100) by serial core? 100 * NSEC_PER_MSEC doesn't
overflow u32.
@@ -145,6 +145,53 @@ static void pci1xxxx_set_divisor(struct uart_port *port, unsigned int baud,
port->membase + UART_BAUD_CLK_DIVISOR_REG);
}
+static int pci1xxxx_rs485_config(struct uart_port *port,
+ struct ktermios *termios,
+ struct serial_rs485 *rs485)
+{
+ u32 clock_div = readl(port->membase + UART_BAUD_CLK_DIVISOR_REG);
+ u64 delay_in_baud_periods;
+ u32 baud_period_in_ns;
+ u32 data = 0;
+
+ /*
+ * pci1xxxx's uart hardware supports only RTS delay after
+ * Tx and in units of bit times to a maximum of 15
+ */
+ if (rs485->flags & SER_RS485_ENABLED) {
+ data = ADCL_CFG_EN | ADCL_CFG_PIN_SEL;
+
+ if (!(rs485->flags & SER_RS485_RTS_ON_SEND))
+ data |= ADCL_CFG_POL_SEL;
+
+ if (rs485->delay_rts_after_send) {
+ baud_period_in_ns =
+ FIELD_GET(BAUD_CLOCK_DIV_INT_MSK, clock_div) *
+ UART_BIT_SAMPLE_CNT;
+ delay_in_baud_periods =
+ rs485->delay_rts_after_send * NSEC_PER_MSEC /
+ baud_period_in_ns;
+ delay_in_baud_periods =
+ min_t(u64, delay_in_baud_periods,
+ FIELD_MAX(ADCL_CFG_RTS_DELAY_MASK));
+ data |= FIELD_PREP(ADCL_CFG_RTS_DELAY_MASK,
+ delay_in_baud_periods);
+ rs485->delay_rts_after_send =
+ baud_period_in_ns * delay_in_baud_periods /
+ NSEC_PER_MSEC;
+ }
+ }
+ writel(data, port->membase + ADCL_CFG_REG);
+ return 0;
+}
+
+static const struct serial_rs485 pci1xxxx_rs485_supported = {
+ .flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND |
+ SER_RS485_RTS_AFTER_SEND,
+ .delay_rts_after_send = 1,
+ /* Delay RTS before send is not supported */
+};
+
static int pci1xxxx_setup(struct pci1xxxx_8250 *priv,
struct uart_8250_port *port, int port_idx)
{
@@ -155,6 +202,8 @@ static int pci1xxxx_setup(struct pci1xxxx_8250 *priv,
port->port.set_termios = serial8250_do_set_termios;
port->port.get_divisor = pci1xxxx_get_divisor;
port->port.set_divisor = pci1xxxx_set_divisor;
+ port->port.rs485_config = pci1xxxx_rs485_config;
+ port->port.rs485_supported = pci1xxxx_rs485_supported;
ret = serial8250_pci_setup_port(priv->pdev, port, 0, port_idx * 256, 0);
if (ret < 0)