[PATCH printk v5 1/1] printk: extend console_lock for per-console locking

[John Ogness]

Hi Marek,

On 2022-05-05, John Ogness <john.ogness at linutronix.de> wrote:
> I will go through and check if all access to AML_UART_CONTROL is
> protected by port->lock.

The startup() callback of the uart_ops is not called with the port
locked. I'm having difficulties identifying if the startup() callback
can occur after the console was already registered via meson_uart_init()
and could be actively printing, but I see other serial drivers are
protecting their registers in the startup() callback with the
port->lock.

Could you try booting the meson hardware with the following change? (And
removing any previous debug changes I posted?)

John

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 2bf1c57e0981..f551b8603817 100644
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -267,9 +267,12 @@ static void meson_uart_reset(struct uart_port *port)
 
 static int meson_uart_startup(struct uart_port *port)
 {
+	unsigned long flags;
 	u32 val;
 	int ret = 0;
 
+	spin_lock_irqsave(&port->lock, flags);
+
 	val = readl(port->membase + AML_UART_CONTROL);
 	val |= AML_UART_CLEAR_ERR;
 	writel(val, port->membase + AML_UART_CONTROL);
@@ -285,6 +288,8 @@ static int meson_uart_startup(struct uart_port *port)
 	val = (AML_UART_RECV_IRQ(1) | AML_UART_XMIT_IRQ(port->fifosize / 2));
 	writel(val, port->membase + AML_UART_MISC);
 
+	spin_unlock_irqrestore(&port->lock, flags);
+
 	ret = request_irq(port->irq, meson_uart_interrupt, 0,
 			  port->name, port);