[PATCH 3/3] serial: mxs-auart: fix IRQ registration ordering and manage console clock

[Rosen Penev]

Move the main UART IRQ registration after uart_add_one_port so that
s->port.state and s->port.lock are initialized before the interrupt
handler can run. Mask all UART interrupts before adding the port to
prevent spurious IRQs left by the bootloader.

After probe succeeds, disable the module clock for non-console ports
since startup will re-enable it on port open. For console ports, keep
the clock prepared so auart_console_write() can safely call
clk_enable() from atomic context.

Assisted-by: opencode:big-pickle
Signed-off-by: Rosen Penev <rosenp at gmail.com>
---
 drivers/tty/serial/mxs-auart.c | 39 ++++++++++++++++++++++++++--------
 1 file changed, 30 insertions(+), 9 deletions(-)

diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index 4499e3206e85..d40d82f112c0 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -1603,10 +1603,6 @@ static int mxs_auart_probe(struct platform_device *pdev)
 	}

 	s->port.irq = irq;
-	ret = devm_request_irq(&pdev->dev, irq, mxs_auart_irq_handle, 0,
-			       dev_name(&pdev->dev), s);
-	if (ret)
-		goto out_disable_clk;

 	platform_set_drvdata(pdev, s);

@@ -1627,9 +1623,28 @@ static int mxs_auart_probe(struct platform_device *pdev)

 	mxs_auart_reset_deassert(s);

+	/* Mask all UART interrupts to prevent spurious IRQs from bootloader */
+	mxs_write(0, s, REG_INTR);
+
 	ret = uart_add_one_port(&auart_driver, &s->port);
-	if (ret)
-		goto out_free_qpio_irq;
+	if (ret) {
+		auart_port[s->port.line] = NULL;
+		goto out_disable_clk;
+	}
+
+	/*
+	 * Request the main IRQ after uart_add_one_port so that
+	 * s->port.state and s->port.lock are initialized before
+	 * the handler can run in response to a bootloader-left
+	 * interrupt.
+	 */
+	ret = devm_request_irq(&pdev->dev, irq, mxs_auart_irq_handle, 0,
+			       dev_name(&pdev->dev), s);
+	if (ret) {
+		uart_remove_one_port(&auart_driver, &s->port);
+		auart_port[s->port.line] = NULL;
+		goto out_disable_clk;
+	}

 	/* ASM9260 don't have version reg */
 	if (is_asm9260_auart(s)) {
@@ -1641,10 +1656,16 @@ static int mxs_auart_probe(struct platform_device *pdev)
 			 (version >> 16) & 0xff, version & 0xffff);
 	}

-	return 0;
+	/*
+	 * Disable clock - startup will re-enable when the port is opened.
+	 * For the console port the clock must stay prepared so that
+	 * auart_console_write() can safely call clk_enable() from
+	 * atomic context.
+	 */
+	if (!uart_console(&s->port))
+		clk_disable_unprepare(s->clk);

-out_free_qpio_irq:
-	auart_port[s->port.line] = NULL;
+	return 0;

 out_disable_clk:
 	clk_disable_unprepare(s->clk);
--
2.54.0