From: Thomas Gleixner Date: Thu, 14 Sep 2023 20:43:28 +0206 Subject: [PATCH 011/134] serial: 8250_mtk: Use port lock wrappers Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz When a serial port is used for kernel console output, then all modifications to the UART registers which are done from other contexts, e.g. getty, termios, are interference points for the kernel console. So far this has been ignored and the printk output is based on the principle of hope. The rework of the console infrastructure which aims to support threaded and atomic consoles, requires to mark sections which modify the UART registers as unsafe. This allows the atomic write function to make informed decisions and eventually to restore operational state. It also allows to prevent the regular UART code from modifying UART registers while printk output is in progress. All modifications of UART registers are guarded by the UART port lock, which provides an obvious synchronization point with the console infrastructure. To avoid adding this functionality to all UART drivers, wrap the spin_[un]lock*() invocations for uart_port::lock into helper functions which just contain the spin_[un]lock*() invocations for now. In a subsequent step these helpers will gain the console synchronization mechanisms. Converted with coccinelle. No functional change. Signed-off-by: Thomas Gleixner Reviewed-by: Chen-Yu Tsai Signed-off-by: John Ogness Link: https://lore.kernel.org/r/20230914183831.587273-12-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sebastian Andrzej Siewior --- drivers/tty/serial/8250/8250_mtk.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/drivers/tty/serial/8250/8250_mtk.c +++ b/drivers/tty/serial/8250/8250_mtk.c @@ -102,7 +102,7 @@ static void mtk8250_dma_rx_complete(void if (data->rx_status == DMA_RX_SHUTDOWN) return; - spin_lock_irqsave(&up->port.lock, flags); + uart_port_lock_irqsave(&up->port, &flags); dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state); total = dma->rx_size - state.residue; @@ -128,7 +128,7 @@ static void mtk8250_dma_rx_complete(void mtk8250_rx_dma(up); - spin_unlock_irqrestore(&up->port.lock, flags); + uart_port_unlock_irqrestore(&up->port, flags); } static void mtk8250_rx_dma(struct uart_8250_port *up) @@ -368,7 +368,7 @@ mtk8250_set_termios(struct uart_port *po * Ok, we're now changing the port state. Do it with * interrupts disabled. */ - spin_lock_irqsave(&port->lock, flags); + uart_port_lock_irqsave(port, &flags); /* * Update the per-port timeout. @@ -416,7 +416,7 @@ mtk8250_set_termios(struct uart_port *po if (uart_console(port)) up->port.cons->cflag = termios->c_cflag; - spin_unlock_irqrestore(&port->lock, flags); + uart_port_unlock_irqrestore(port, flags); /* Don't rewrite B0 */ if (tty_termios_baud_rate(termios)) tty_termios_encode_baud_rate(termios, baud, baud);