From: s.hauer@pengutronix.de (Sascha Hauer)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] imx: add polled io uart methods
Date: Mon, 17 Oct 2011 22:17:25 +0200 [thread overview]
Message-ID: <20111017201725.GG18141@pengutronix.de> (raw)
In-Reply-To: <1318821721-11965-2-git-send-email-compnerd@compnerd.org>
On Sun, Oct 16, 2011 at 08:22:01PM -0700, Saleem Abdulrasool wrote:
> These methods are invoked if the iMX uart is used in conjuction with kgdb during
> early boot. In order to access the UART without the interrupts, the kernel uses
> the basic polling methods for IO with the device. With these methods
> implemented, it is now possible to enable kgdb during early boot over serial.
>
> Signed-off-by: Saleem Abdulrasool <compnerd@compnerd.org>
> ---
> drivers/tty/serial/imx.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 77 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 7e91b3d..4fcf9ca 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -102,6 +102,7 @@
> #define UCR2_STPB (1<<6) /* Stop */
> #define UCR2_WS (1<<5) /* Word size */
> #define UCR2_RTSEN (1<<4) /* Request to send interrupt enable */
> +#define UCR2_ATEN (1<<3) /* Aging Timer Enable */
> #define UCR2_TXEN (1<<2) /* Transmitter enabled */
> #define UCR2_RXEN (1<<1) /* Receiver enabled */
> #define UCR2_SRST (1<<0) /* SW reset */
> @@ -1075,6 +1076,77 @@ imx_verify_port(struct uart_port *port, struct serial_struct *ser)
> return ret;
> }
>
> +
> +#if defined(CONFIG_CONSOLE_POLL)
> +static int imx_poll_get_char(struct uart_port *port)
> +{
> + volatile unsigned int status;
> + unsigned int cr1, cr2, cr3;
> + unsigned char c;
> +
> + /* save control registers */
> + cr1 = readl(port->membase + UCR1);
> + cr2 = readl(port->membase + UCR2);
> + cr3 = readl(port->membase + UCR3);
> +
> + /* disable interrupts */
> + writel(UCR1_UARTEN, port->membase + UCR1);
> + writel(cr2 & ~(UCR2_ATEN | UCR2_RTSEN | UCR2_ESCI),
> + port->membase + UCR2);
> + writel(cr3 & ~(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 */
> + writel(cr1, port->membase + UCR1);
> + writel(cr2, port->membase + UCR2);
> + writel(cr3, port->membase + UCR3);
> +
> + return (c & 0xff);
> +}
> +
> +static void imx_poll_put_char(struct uart_port *port, unsigned char c)
> +{
> + volatile unsigned int status;
> + unsigned int cr1, cr2, cr3;
> +
> + /* save control registers */
> + cr1 = readl(port->membase + UCR1);
> + cr2 = readl(port->membase + UCR2);
> + cr3 = readl(port->membase + UCR3);
> +
> + /* disable interrupts */
> + writel(UCR1_UARTEN, port->membase + UCR1);
> + writel(cr2 & ~(UCR2_ATEN | UCR2_RTSEN | UCR2_ESCI),
> + port->membase + UCR2);
> + writel(cr3 & ~(UCR3_DCD | UCR3_RI | UCR3_DTREN), port->membase + UCR3);
> +
> + /* drain */
> + do {
> + status = readl(port->membase + USR1);
> + } while (~status & USR1_TRDY);
> +
> + /* write */
> + writel(c, port->membase + URTX0);
> +
> + /* flush */
> + do {
> + status = readl(port->membase + USR2);
> + } while (~status & USR2_TXDC);
> +
> + /* restore control registers */
> + writel(cr1, port->membase + UCR1);
> + writel(cr2, port->membase + UCR2);
> + writel(cr3, port->membase + UCR3);
> +}
We should factor out the uart save/restore functionality instead of
having the same code three times in the driver. I'm thinking about:
imx_console_mode(struct uart_port *port, u32 *ucr1, u32 *ucr2, u32 *ucr2);
imx_console_restore(struct uart_port *port, u32 ucr1, u32 ucr2, u32 ucr3);
These functions could correctly handle ucr3 (which is missing in
mainline) and i.MX1 (which is missing in your patch).
Sascha
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next prev parent reply other threads:[~2011-10-17 20:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-19 1:45 No subject Saleem Abdulrasool
2011-09-19 1:45 ` [PATCH] mxcuart: add polled io methods Saleem Abdulrasool
2011-09-21 3:50 ` Fabio Estevam
2011-10-17 3:22 ` [PATCH] imx: add polled io uart methods Saleem Abdulrasool
2011-10-17 3:22 ` Saleem Abdulrasool
2011-10-17 19:44 ` Fabio Estevam
2011-10-17 20:17 ` Sascha Hauer [this message]
2011-12-04 17:01 ` Dirk Behme
2011-10-18 7:27 ` Uwe Kleine-König
2011-10-19 3:52 ` Saleem Abdulrasool
2011-12-01 10:32 ` Dirk Behme
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