serial: imx: get rid of unbounded busy-waiting loop (2eda5345) · Commits · 戴 / test

imx_set_termios(): remove busy-waiting "drain Tx FIFO" loop. Worse yet, it was potentially unbounded wait due to RTS/CTS (hardware) handshake. Let user space ensure draining is done before termios change, if draining is needed in the first place. Signed-off-by:

Sergey Organov <sorganov@gmail.com> Link: https://lore.kernel.org/r/1567017475-11919-2-git-send-email-sorganov@gmail.com Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -1644,7 +1644,7 @@ imx_uart_set_termios(struct uart_port port, struct ktermios termios,
		uart_update_timeout(port, termios->c_cflag, baud);

		/*
		* disable interrupts and drain transmitter
		* disable interrupts
		*/
		old_ucr1 = imx_uart_readl(sport, UCR1);
		imx_uart_writel(sport,
		@@ -1652,9 +1652,6 @@ imx_uart_set_termios(struct uart_port port, struct ktermios termios,
		UCR1);
		imx_uart_writel(sport, old_ucr2 & ~UCR2_ATEN, UCR2);

		while (!(imx_uart_readl(sport, USR2) & USR2_TXDC))
		barrier();

		/* then, disable everything */
		imx_uart_writel(sport, old_ucr2 & ~(UCR2_TXEN \| UCR2_RXEN \| UCR2_ATEN), UCR2);

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