serial: imx: clean up imx_poll_get_char() (26c47412) · Commits · 戴 / test

Looking at the get_poll_char() function of the 8250.c serial driver, we learn: * poll_get_char() doesn't have to save/disable/restore the interrupt registers. No interrupt handling is needed in this function at all. Remove it. * Don't block in case there is no data available. So instead blocking in the do {} while loop, just return with NO_POLL_CHAR, immediately . Additionally, while the i.MX6 register URXD[7-0] contain the RX_DATA, the upper bits of this register (URXD[15-10]) might contain some control flags. To ensure that these are not returned with the data read, just mask out URXD[7-0]. These changes fix the 'hang' working with kdb: $ echo ttymxc3 > /sys/module/kgdboc/parameters/kgdboc $ echo g >/proc/sysrq-trigger [0]kdb> help ... <hang> Signed-off-by:

Dirk Behme <dirk.behme@de.bosch.com> Signed-off-by:

Daniel Thompson <daniel.thompson@linaro.org> Cc: Jiri Slaby <jslaby@suse.cz> Cc: linux-serial@vger.kernel.org Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

+4 −25

Original line number	Diff line number	Diff line
		@@ -80,6 +80,7 @@
		#define URXD_FRMERR (1<<12)
		#define URXD_BRK (1<<11)
		#define URXD_PRERR (1<<10)
		#define URXD_RX_DATA (0xFF<<0)
		#define UCR1_ADEN (1<<15) /* Auto detect interrupt */
		#define UCR1_ADBR (1<<14) /* Auto detect baud rate */
		#define UCR1_TRDYEN (1<<13) /* Transmitter ready interrupt enable */
		@@ -1499,32 +1500,10 @@ imx_verify_port(struct uart_port port, struct serial_struct ser)
		#if defined(CONFIG_CONSOLE_POLL)
		static int imx_poll_get_char(struct uart_port *port)
		{
		struct imx_port_ucrs old_ucr;
		unsigned int status;
		unsigned char c;

		/* save control registers */
		imx_port_ucrs_save(port, &old_ucr);

		/* disable interrupts */
		writel(UCR1_UARTEN, port->membase + UCR1);
		writel(old_ucr.ucr2 & ~(UCR2_ATEN \| UCR2_RTSEN \| UCR2_ESCI),
		port->membase + UCR2);
		writel(old_ucr.ucr3 & ~(UCR3_DCD \| UCR3_RI \| UCR3_DTREN),
		port->membase + UCR3);

		/* poll */
		do {
		status = readl(port->membase + USR2);
		} while (~status & USR2_RDR);

		/* read */
		c = readl(port->membase + URXD0);

		/* restore control registers */
		imx_port_ucrs_restore(port, &old_ucr);
		if (!(readl(port->membase + USR2) & USR2_RDR))
		return NO_POLL_CHAR;

		return c;
		return readl(port->membase + URXD0) & URXD_RX_DATA;
		}

		static void imx_poll_put_char(struct uart_port *port, unsigned char c)

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