serial: qcom-geni: fix opp vote on shutdown

commit 8ece7b7 upstream.

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: a5819b5 ("tty: serial: qcom_geni_serial: Use OPP API to set clk/perf state")
Cc: stable@vger.kernel.org      # 5.9
Cc: Rajendra Nayak <quic_rjendra@quicinc.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Acked-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20230714130214.14552-2-johan+linaro@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/qcom_geni_serial.c

@@ -129,6 +129,7 @@ struct qcom_geni_serial_port {
 	u32 tx_fifo_width;
 	u32 rx_fifo_depth;
 	bool setup;
+	unsigned long clk_rate;
 	int (*handle_rx)(struct uart_port *uport, u32 bytes, bool drop);
 	unsigned int baud;
 	void *rx_fifo;
@@ -1061,6 +1062,7 @@ 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;
@@ -1330,10 +1332,13 @@ 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);
 	}
 }