linux-kernel - [PATCH 16/36] serial: imx: Fill in rs485

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Date:   Mon,  6 Jun 2022 13:04:13 +0300
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     linux-serial@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: [PATCH 16/36] serial: imx: Fill in rs485_supported

Add information on supported serial_rs485 features.

In the case where RTS is lacking, RS485 cannot be enabled so provide
zero rs485_supported for that case. Perhaps it would make sense to not
provide rs485_config() at all in that case but such a change would have
userspace visible impact/change in behavior so this patch does not
attempt it.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 drivers/tty/serial/imx.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 9ce09b81ac9b..ba853bc9b4db 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2200,6 +2200,14 @@ static enum hrtimer_restart imx_trigger_stop_tx(struct hrtimer *t)
 	return HRTIMER_NORESTART;
 }
 
+static const struct serial_rs485 imx_no_rs485 = {};	/* No RS485 if no RTS */
+static const struct serial_rs485 imx_rs485_supported = {
+	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND |
+		 SER_RS485_RX_DURING_TX,
+	.delay_rts_before_send = 1,
+	.delay_rts_after_send = 1,
+};
+
 /* Default RX DMA buffer configuration */
 #define RX_DMA_PERIODS		16
 #define RX_DMA_PERIOD_LEN	(PAGE_SIZE / 4)
@@ -2279,6 +2287,11 @@ static int imx_uart_probe(struct platform_device *pdev)
 	sport->port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_IMX_CONSOLE);
 	sport->port.ops = &imx_uart_pops;
 	sport->port.rs485_config = imx_uart_rs485_config;
+	/* RTS is required to control the RS485 transmitter */
+	if (sport->have_rtscts || sport->have_rtsgpio)
+		sport->port.rs485_supported = &imx_rs485_supported;
+	else
+		sport->port.rs485_supported = &imx_no_rs485;
 	sport->port.flags = UPF_BOOT_AUTOCONF;
 	timer_setup(&sport->timer, imx_uart_timeout, 0);
 
-- 
2.30.2