serial: do not restore interrupt state in sysrq helper

The uart_unlock_and_check_sysrq() helper can be used to defer processing
of sysrq until the interrupt handler has released the port lock and is
about to return.

Since commit 81e2073c175b ("genirq: Disable interrupts for force
threaded handlers") interrupt handlers that are not explicitly requested
as threaded are always called with interrupts disabled and there is no
need to save the interrupt state when taking the port lock.

Instead of adding another sysrq helper for when the interrupt state has
not needlessly been saved, drop the state parameter from
uart_unlock_and_check_sysrq() and update its callers to no longer
explicitly disable interrupts in their interrupt handlers.

Cc: Joel Stanley <[e-mail]>
Cc: Andrew Jeffery <[e-mail]>
Cc: Andy Gross <[e-mail]>
Cc: Bjorn Andersson <[e-mail]>
Signed-off-by: Johan Hovold <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/8250/8250_aspeed_vuart.c

···
 {
 	struct uart_8250_port *up = up_to_u8250p(port);
 	unsigned int iir, lsr;
-	unsigned long flags;
 	int space, count;
 
 	iir = serial_port_in(port, UART_IIR);
···
 	if (iir & UART_IIR_NO_INT)
 		return 0;
 
-	spin_lock_irqsave(&port->lock, flags);
+	spin_lock(&port->lock);
 
 	lsr = serial_port_in(port, UART_LSR);
 
···
 	if (lsr & UART_LSR_THRE)
 		serial8250_tx_chars(up);
 
-	uart_unlock_and_check_sysrq(port, flags);
+	uart_unlock_and_check_sysrq(port);
 
 	return 1;
 }

drivers/tty/serial/8250/8250_fsl.c

···
 int fsl8250_handle_irq(struct uart_port *port)
 {
 	unsigned char lsr, orig_lsr;
-	unsigned long flags;
 	unsigned int iir;
 	struct uart_8250_port *up = up_to_u8250p(port);
 
-	spin_lock_irqsave(&up->port.lock, flags);
+	spin_lock(&up->port.lock);
 
 	iir = port->serial_in(port, UART_IIR);
 	if (iir & UART_IIR_NO_INT) {
-		spin_unlock_irqrestore(&up->port.lock, flags);
+		spin_unlock(&up->port.lock);
 		return 0;
 	}
 
···
 	if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
 		up->lsr_saved_flags &= ~UART_LSR_BI;
 		port->serial_in(port, UART_RX);
-		spin_unlock_irqrestore(&up->port.lock, flags);
+		spin_unlock(&up->port.lock);
 		return 1;
 	}
 
···
 		serial8250_tx_chars(up);
 
 	up->lsr_saved_flags = orig_lsr;
-	uart_unlock_and_check_sysrq(&up->port, flags);
+
+	uart_unlock_and_check_sysrq(&up->port);
+
 	return 1;
 }
 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);

drivers/tty/serial/8250/8250_omap.c

···
 	struct uart_8250_port *up = up_to_u8250p(port);
 	struct omap8250_priv *priv = up->port.private_data;
 	unsigned char status;
-	unsigned long flags;
 	u8 iir;
 
 	serial8250_rpm_get(up);
···
 		return IRQ_HANDLED;
 	}
 
-	spin_lock_irqsave(&port->lock, flags);
+	spin_lock(&port->lock);
 
 	status = serial_port_in(port, UART_LSR);
 
···
 		}
 	}
 
-	uart_unlock_and_check_sysrq(port, flags);
+	uart_unlock_and_check_sysrq(port);
+
 	serial8250_rpm_put(up);
 	return 1;
 }

drivers/tty/serial/8250/8250_port.c

···
 int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 {
 	unsigned char status;
-	unsigned long flags;
 	struct uart_8250_port *up = up_to_u8250p(port);
 	bool skip_rx = false;
 
 	if (iir & UART_IIR_NO_INT)
 		return 0;
 
-	spin_lock_irqsave(&port->lock, flags);
+	spin_lock(&port->lock);
 
 	status = serial_port_in(port, UART_LSR);
 
···
 		(up->ier & UART_IER_THRI))
 		serial8250_tx_chars(up);
 
-	uart_unlock_and_check_sysrq(port, flags);
+	uart_unlock_and_check_sysrq(port);
+
 	return 1;
 }
 EXPORT_SYMBOL_GPL(serial8250_handle_irq);

drivers/tty/serial/qcom_geni_serial.c

···
 	u32 s_irq_status;
 	u32 geni_status;
 	struct uart_port *uport = dev;
-	unsigned long flags;
 	bool drop_rx = false;
 	struct tty_port *tport = &uport->state->port;
 	struct qcom_geni_serial_port *port = to_dev_port(uport, uport);
···
 	if (uport->suspended)
 		return IRQ_NONE;
 
-	spin_lock_irqsave(&uport->lock, flags);
+	spin_lock(&uport->lock);
+
 	m_irq_status = readl(uport->membase + SE_GENI_M_IRQ_STATUS);
 	s_irq_status = readl(uport->membase + SE_GENI_S_IRQ_STATUS);
 	geni_status = readl(uport->membase + SE_GENI_STATUS);
···
 		qcom_geni_serial_handle_rx(uport, drop_rx);
 
 out_unlock:
-	uart_unlock_and_check_sysrq(uport, flags);
+	uart_unlock_and_check_sysrq(uport);
 
 	return IRQ_HANDLED;
 }

include/linux/serial_core.h

···
 	return 0;
 }
 
-static inline void uart_unlock_and_check_sysrq(struct uart_port *port, unsigned long irqflags)
+static inline void uart_unlock_and_check_sysrq(struct uart_port *port)
 {
 	int sysrq_ch;
 
 	if (!port->has_sysrq) {
-		spin_unlock_irqrestore(&port->lock, irqflags);
+		spin_unlock(&port->lock);
 		return;
 	}
 
 	sysrq_ch = port->sysrq_ch;
 	port->sysrq_ch = 0;
 
-	spin_unlock_irqrestore(&port->lock, irqflags);
+	spin_unlock(&port->lock);
 
 	if (sysrq_ch)
 		handle_sysrq(sysrq_ch);
···
 {
 	return 0;
 }
-static inline void uart_unlock_and_check_sysrq(struct uart_port *port, unsigned long irqflags)
+static inline void uart_unlock_and_check_sysrq(struct uart_port *port)
 {
-	spin_unlock_irqrestore(&port->lock, irqflags);
+	spin_unlock(&port->lock);
 }
 #endif	/* CONFIG_MAGIC_SYSRQ_SERIAL */