linux-kernel - [PATCH 1/2] serial: qcom-geni: fix opp vote on shutdown

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Date:   Fri, 14 Jul 2023 15:02:13 +0200
From:   Johan Hovold <johan+linaro@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Johan Hovold <johan+linaro@...nel.org>, stable@...r.kernel.org,
        Rajendra Nayak <quic_rjendra@...cinc.com>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [PATCH 1/2] serial: qcom-geni: fix opp vote on shutdown

The operating-performance-point vote needs to be dropped when shutting
down the port to avoid wasting power by keeping resources like power
domains in an unnecessarily high performance state (e.g. when a UART
connected Bluetooth controller is not in use).

Fixes: a5819b548af0 ("tty: serial: qcom_geni_serial: Use OPP API to set clk/perf state")
Cc: stable@...r.kernel.org      # 5.9
Cc: Rajendra Nayak <quic_rjendra@...cinc.com>
Cc: Matthias Kaehlcke <mka@...omium.org>
Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
---
 drivers/tty/serial/qcom_geni_serial.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index b825b05e6137..8be896dbaa88 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -126,6 +126,7 @@ struct qcom_geni_serial_port {
 	dma_addr_t rx_dma_addr;
 	bool setup;
 	unsigned int baud;
+	unsigned long clk_rate;
 	void *rx_buf;
 	u32 loopback;
 	bool brk;
@@ -1249,6 +1250,7 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport,
 			baud * sampling_rate, clk_rate, clk_div);
 
 	uport->uartclk = clk_rate;
+	port->clk_rate = clk_rate;
 	dev_pm_opp_set_rate(uport->dev, clk_rate);
 	ser_clk_cfg = SER_CLK_EN;
 	ser_clk_cfg |= clk_div << CLK_DIV_SHFT;
@@ -1513,10 +1515,13 @@ static void qcom_geni_serial_pm(struct uart_port *uport,
 
 	if (new_state == UART_PM_STATE_ON && old_state == UART_PM_STATE_OFF) {
 		geni_icc_enable(&port->se);
+		if (port->clk_rate)
+			dev_pm_opp_set_rate(uport->dev, port->clk_rate);
 		geni_se_resources_on(&port->se);
 	} else if (new_state == UART_PM_STATE_OFF &&
 			old_state == UART_PM_STATE_ON) {
 		geni_se_resources_off(&port->se);
+		dev_pm_opp_set_rate(uport->dev, 0);
 		geni_icc_disable(&port->se);
 	}
 }
-- 
2.41.0