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authorDaniel Thompson <daniel.thompson@linaro.org>2014-06-18 10:46:16 +0100
committerDaniel Thompson <daniel.thompson@linaro.org>2014-10-20 13:27:00 +0100
commitf6cc5415a886f962e6909d4e2a9a2e50ec4ad26f (patch)
treeef00c5ccb452145b7acba5aec5e62f220808b851
parent5ed7c2c21cbf12476d55c0d5ae9a5737ebeac0da (diff)
downloadlinux-dev/kdb-fiq.tar.gz
serial: imx: Add support for KGDB's FIQ/NMI modedev/kdb-fiq
This patch makes it possible to use the imx uart with KGDB's FIQ/NMI mode. Main changes are: .poll_init() will, if KGDB+FIQ are enabled, perform deeper hardware initialization to ensure the serial port is always active (required otherwise FIQ is not triggered by UART activity). This has an impact on power usage so it is conservatively enabled. imx_put_poll_char() has been simplified to remove the code to disable interrupts. The present code can corrupt register state when re-entered from FIQ handler. Both imx_put_poll_char() and imx_get_poll_char() adopt _relaxed() MMIO functions (which are safe for polled I/O and needed to avoid taking spin locks). Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jiri Slaby <jslaby@suse.cz> Cc: linux-serial@vger.kernel.org Acked-by: Dirk Behme <dirk.behme@de.bosch.com>
-rw-r--r--drivers/tty/serial/imx.c71
1 files changed, 52 insertions, 19 deletions
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 8f62a3cec23e..883f8a2f4ab5 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -49,6 +49,7 @@
#include <linux/of_device.h>
#include <linux/io.h>
#include <linux/dma-mapping.h>
+#include <linux/kgdb.h>
#include <asm/irq.h>
#include <linux/platform_data/serial-imx.h>
@@ -1507,44 +1508,73 @@ imx_verify_port(struct uart_port *port, struct serial_struct *ser)
}
#if defined(CONFIG_CONSOLE_POLL)
+
+#if defined(CONFIG_KGDB_FIQ)
+/*
+ * Prepare the UART to be used from kgdb's NMI support.
+ */
+static int imx_poll_init(struct uart_port *port)
+{
+ struct imx_port *sport = (struct imx_port *)port;
+ unsigned long flags;
+ unsigned long temp;
+ int retval;
+
+ retval = clk_prepare_enable(sport->clk_ipg);
+ if (retval)
+ return retval;
+ retval = clk_prepare_enable(sport->clk_per);
+ if (retval)
+ clk_disable_unprepare(sport->clk_ipg);
+
+ imx_setup_ufcr(sport, 0);
+
+ spin_lock_irqsave(&sport->port.lock, flags);
+
+ temp = readl(sport->port.membase + UCR1);
+ if (is_imx1_uart(sport))
+ temp |= IMX1_UCR1_UARTCLKEN;
+ temp |= UCR1_UARTEN | UCR1_RRDYEN;
+ temp &= ~(UCR1_TXMPTYEN | UCR1_RTSDEN);
+ writel(temp, sport->port.membase + UCR1);
+
+ temp = readl(sport->port.membase + UCR2);
+ temp |= UCR2_RXEN;
+ writel(temp, sport->port.membase + UCR2);
+
+ spin_unlock_irqrestore(&sport->port.lock, flags);
+
+ /* register the FIQ with kgdb */
+ kgdb_register_fiq(sport->port.irq);
+
+ return 0;
+}
+#endif /* CONFIG_KGDB_FIQ */
+
static int imx_poll_get_char(struct uart_port *port)
{
- if (!(readl(port->membase + USR2) & USR2_RDR))
+ if (!(readl_relaxed(port->membase + USR2) & USR2_RDR))
return NO_POLL_CHAR;
- return readl(port->membase + URXD0) & URXD_RX_DATA;
+ return readl_relaxed(port->membase + URXD0) & URXD_RX_DATA;
}
static void imx_poll_put_char(struct uart_port *port, unsigned char c)
{
- struct imx_port_ucrs old_ucr;
unsigned int status;
- /* 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);
-
/* drain */
do {
- status = readl(port->membase + USR1);
+ status = readl_relaxed(port->membase + USR1);
} while (~status & USR1_TRDY);
/* write */
- writel(c, port->membase + URTX0);
+ writel_relaxed(c, port->membase + URTX0);
/* flush */
do {
- status = readl(port->membase + USR2);
+ status = readl_relaxed(port->membase + USR2);
} while (~status & USR2_TXDC);
-
- /* restore control registers */
- imx_port_ucrs_restore(port, &old_ucr);
}
#endif
@@ -1565,6 +1595,9 @@ static struct uart_ops imx_pops = {
.config_port = imx_config_port,
.verify_port = imx_verify_port,
#if defined(CONFIG_CONSOLE_POLL)
+#if defined(CONFIG_KGDB_FIQ)
+ .poll_init = imx_poll_init,
+#endif
.poll_get_char = imx_poll_get_char,
.poll_put_char = imx_poll_put_char,
#endif