linux-kernel - [PATCH] drivers/tty/serial/qcom-geni-serial: Do stop_rx in suspend path for console if console

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Message-Id: <1648491444-17137-1-git-send-email-quic_vnivarth@quicinc.com>
Date:   Mon, 28 Mar 2022 23:47:24 +0530
From:   Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
To:     agross@...nel.org, bjorn.andersson@...aro.org,
        gregkh@...uxfoundation.org, jirislaby@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     quic_msavaliy@...cinc.com, dianders@...omium.org,
        Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
Subject: [PATCH] drivers/tty/serial/qcom-geni-serial: Do stop_rx in suspend path for console if console_suspend is disabled

[Why]
For the case of console_suspend disabled, if back to back suspend/resume
test is executed, at the end of test, sometimes console would appear to
be frozen not responding to input. This would happen because, for
console_suspend disabled, suspend/resume routines only turn resources
off/on but don't do a port close/open.
As a result, during resume, some rx transactions come in before system is
ready, malfunction of rx happens in turn resulting in console appearing
to be stuck.

[How]
Do a stop_rx in suspend sequence to prevent this. start_rx is already
present in resume sequence as part of call to set_termios which does a
stop_rx/start_rx.
Additionally other changes have been made at same place
a) replace the hardcoded flags with macros
b) perform voting before calling resume_port in resume sequence
c) consequently, swap the order in suspend sequence

Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
---
 drivers/tty/serial/qcom_geni_serial.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index aedc388..37d064f 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -19,6 +19,7 @@
 #include <linux/slab.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
+#include <dt-bindings/interconnect/qcom,icc.h>
 
 /* UART specific GENI registers */
 #define SE_UART_LOOPBACK_CFG		0x22c
@@ -1477,34 +1478,38 @@ static int qcom_geni_serial_remove(struct platform_device *pdev)
 
 static int __maybe_unused qcom_geni_serial_sys_suspend(struct device *dev)
 {
+	int ret;
 	struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
 	struct uart_port *uport = &port->uport;
 	struct qcom_geni_private_data *private_data = uport->private_data;
 
+	/* do a stop_rx here, start_rx is handled in uart_resume_port by call to setermios */
+	if (!console_suspend_enabled && uart_console(uport))
+		uport->ops->stop_rx(uport);
+
 	/*
 	 * This is done so we can hit the lowest possible state in suspend
 	 * even with no_console_suspend
 	 */
+	ret = uart_suspend_port(private_data->drv, uport);
 	if (uart_console(uport)) {
-		geni_icc_set_tag(&port->se, 0x3);
+		geni_icc_set_tag(&port->se, QCOM_ICC_TAG_ACTIVE_ONLY);
 		geni_icc_set_bw(&port->se);
 	}
-	return uart_suspend_port(private_data->drv, uport);
+	return ret;
 }
 
 static int __maybe_unused qcom_geni_serial_sys_resume(struct device *dev)
 {
-	int ret;
 	struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
 	struct uart_port *uport = &port->uport;
 	struct qcom_geni_private_data *private_data = uport->private_data;
 
-	ret = uart_resume_port(private_data->drv, uport);
 	if (uart_console(uport)) {
-		geni_icc_set_tag(&port->se, 0x7);
+		geni_icc_set_tag(&port->se, QCOM_ICC_TAG_ALWAYS);
 		geni_icc_set_bw(&port->se);
 	}
-	return ret;
+	return uart_resume_port(private_data->drv, uport);
 }
 
 static const struct dev_pm_ops qcom_geni_serial_pm_ops = {
-- 
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