diff mbox series

[1/2] serial: 8250-mtk: add follow control

Message ID 1556181691-10293-2-git-send-email-long.cheng@mediatek.com (mailing list archive)
State New, archived
Headers show
Series Perfect 8250 mtk uart function. | expand

Commit Message

Long Cheng April 25, 2019, 8:41 a.m. UTC 
Add SW and HW follow control function.

Signed-off-by: Long Cheng <long.cheng@mediatek.com>
---
 drivers/tty/serial/8250/8250_mtk.c |   60 ++++++++++++++++++++++--------------
 1 file changed, 37 insertions(+), 23 deletions(-)

Comments

Matthias Brugger April 25, 2019, 10:40 a.m. UTC | #1 
On 25/04/2019 10:41, Long Cheng wrote:
> Add SW and HW follow control function.

Can you please explain a bit more what you are doing in this patch.
You change the setting of the registers for different baud rates. Please
elaborate what is happening there.

> 
> Signed-off-by: Long Cheng <long.cheng@mediatek.com>
> ---
>  drivers/tty/serial/8250/8250_mtk.c |   60 ++++++++++++++++++++++--------------
>  1 file changed, 37 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
> index c1fdbc0..959fd85 100644
> --- a/drivers/tty/serial/8250/8250_mtk.c
> +++ b/drivers/tty/serial/8250/8250_mtk.c
> @@ -21,12 +21,14 @@
>  
>  #include "8250.h"
>  
> -#define UART_MTK_HIGHS		0x09	/* Highspeed register */
> -#define UART_MTK_SAMPLE_COUNT	0x0a	/* Sample count register */
> -#define UART_MTK_SAMPLE_POINT	0x0b	/* Sample point register */
> +#define MTK_UART_HIGHS		0x09	/* Highspeed register */
> +#define MTK_UART_SAMPLE_COUNT	0x0a	/* Sample count register */
> +#define MTK_UART_SAMPLE_POINT	0x0b	/* Sample point register */

Rename looks good to me. But I'd prefer to have it in a separate patch.

>  #define MTK_UART_RATE_FIX	0x0d	/* UART Rate Fix Register */
> -
>  #define MTK_UART_DMA_EN		0x13	/* DMA Enable register */
> +#define MTK_UART_RXTRI_AD	0x14	/* RX Trigger address */
> +#define MTK_UART_FRACDIV_L	0x15	/* Fractional divider LSB address */
> +#define MTK_UART_FRACDIV_M	0x16	/* Fractional divider MSB address */
>  #define MTK_UART_DMA_EN_TX	0x2
>  #define MTK_UART_DMA_EN_RX	0x5
>  
> @@ -46,6 +48,7 @@ enum dma_rx_status {
>  struct mtk8250_data {
>  	int			line;
>  	unsigned int		rx_pos;
> +	unsigned int		clk_count;

What is that for, not used in this patch.

>  	struct clk		*uart_clk;
>  	struct clk		*bus_clk;
>  	struct uart_8250_dma	*dma;
> @@ -196,9 +199,15 @@ static void mtk8250_shutdown(struct uart_port *port)
>  mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
>  			struct ktermios *old)
>  {
> +	unsigned short fraction_L_mapping[] = {
> +		0, 1, 0x5, 0x15, 0x55, 0x57, 0x57, 0x77, 0x7F, 0xFF, 0xFF
> +	};
> +	unsigned short fraction_M_mapping[] = {
> +		0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 3
> +	};
>  	struct uart_8250_port *up = up_to_u8250p(port);
> +	unsigned int baud, quot, fraction;
>  	unsigned long flags;
> -	unsigned int baud, quot;
>  
>  #ifdef CONFIG_SERIAL_8250_DMA
>  	if (up->dma) {
> @@ -214,7 +223,7 @@ static void mtk8250_shutdown(struct uart_port *port)
>  	serial8250_do_set_termios(port, termios, old);
>  
>  	/*
> -	 * Mediatek UARTs use an extra highspeed register (UART_MTK_HIGHS)
> +	 * Mediatek UARTs use an extra highspeed register (MTK_UART_HIGHS)
>  	 *
>  	 * We need to recalcualte the quot register, as the claculation depends
>  	 * on the vaule in the highspeed register.
> @@ -230,18 +239,11 @@ static void mtk8250_shutdown(struct uart_port *port)
>  				  port->uartclk / 16 / UART_DIV_MAX,
>  				  port->uartclk);
>  
> -	if (baud <= 115200) {
> -		serial_port_out(port, UART_MTK_HIGHS, 0x0);
> +	if (baud < 115200) {
> +		serial_port_out(port, MTK_UART_HIGHS, 0x0);
>  		quot = uart_get_divisor(port, baud);
> -	} else if (baud <= 576000) {
> -		serial_port_out(port, UART_MTK_HIGHS, 0x2);
> -
> -		/* Set to next lower baudrate supported */
> -		if ((baud == 500000) || (baud == 576000))
> -			baud = 460800;
> -		quot = DIV_ROUND_UP(port->uartclk, 4 * baud);

So we allow now also these baud rates? Then you have to update the comment as well.

Regards,
Matthias

>  	} else {
> -		serial_port_out(port, UART_MTK_HIGHS, 0x3);
> +		serial_port_out(port, MTK_UART_HIGHS, 0x3);
>  		quot = DIV_ROUND_UP(port->uartclk, 256 * baud);
>  	}
>  
> @@ -258,17 +260,29 @@ static void mtk8250_shutdown(struct uart_port *port)
>  	/* reset DLAB */
>  	serial_port_out(port, UART_LCR, up->lcr);
>  
> -	if (baud > 460800) {
> +	if (baud >= 115200) {
>  		unsigned int tmp;
>  
> -		tmp = DIV_ROUND_CLOSEST(port->uartclk, quot * baud);
> -		serial_port_out(port, UART_MTK_SAMPLE_COUNT, tmp - 1);
> -		serial_port_out(port, UART_MTK_SAMPLE_POINT,
> -					(tmp - 2) >> 1);
> +		tmp = (port->uartclk / (baud *  quot)) - 1;
> +		serial_port_out(port, MTK_UART_SAMPLE_COUNT, tmp);
> +		serial_port_out(port, MTK_UART_SAMPLE_POINT,
> +					(tmp >> 1) - 1);
> +
> +		/*count fraction to set fractoin register */
> +		fraction = ((port->uartclk  * 100) / baud / quot) % 100;
> +		fraction = DIV_ROUND_CLOSEST(fraction, 10);
> +		serial_port_out(port, MTK_UART_FRACDIV_L,
> +						fraction_L_mapping[fraction]);
> +		serial_port_out(port, MTK_UART_FRACDIV_M,
> +						fraction_M_mapping[fraction]);
>  	} else {
> -		serial_port_out(port, UART_MTK_SAMPLE_COUNT, 0x00);
> -		serial_port_out(port, UART_MTK_SAMPLE_POINT, 0xff);
> +		serial_port_out(port, MTK_UART_SAMPLE_COUNT, 0x00);
> +		serial_port_out(port, MTK_UART_SAMPLE_POINT, 0xff);
> +		serial_port_out(port, MTK_UART_FRACDIV_L, 0x00);
> +		serial_port_out(port, MTK_UART_FRACDIV_M, 0x00);
>  	}
> +	if (uart_console(port))
> +		up->port.cons->cflag = termios->c_cflag;
>  
>  	spin_unlock_irqrestore(&port->lock, flags);
>  	/* Don't rewrite B0 */
>
Long Cheng April 26, 2019, 5:22 a.m. UTC | #2 
On Thu, 2019-04-25 at 12:40 +0200, Matthias Brugger wrote:
> 
> On 25/04/2019 10:41, Long Cheng wrote:
> > Add SW and HW follow control function.
> 
> Can you please explain a bit more what you are doing in this patch.
> You change the setting of the registers for different baud rates. Please
> elaborate what is happening there.
> 
Clock source is different. Sometimes, baudrate is greater than or equal
to 115200, we use highspeed of 3 algorithm and fractional divider to
ensure more accurate baudrate.

Next release version, I will update this to commit message

> > 
> > Signed-off-by: Long Cheng <long.cheng@mediatek.com>
> > ---
> >  drivers/tty/serial/8250/8250_mtk.c |   60 ++++++++++++++++++++++--------------
> >  1 file changed, 37 insertions(+), 23 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
> > index c1fdbc0..959fd85 100644
> > --- a/drivers/tty/serial/8250/8250_mtk.c
> > +++ b/drivers/tty/serial/8250/8250_mtk.c
> > @@ -21,12 +21,14 @@
> >  
> >  #include "8250.h"
> >  
> > -#define UART_MTK_HIGHS		0x09	/* Highspeed register */
> > -#define UART_MTK_SAMPLE_COUNT	0x0a	/* Sample count register */
> > -#define UART_MTK_SAMPLE_POINT	0x0b	/* Sample point register */
> > +#define MTK_UART_HIGHS		0x09	/* Highspeed register */
> > +#define MTK_UART_SAMPLE_COUNT	0x0a	/* Sample count register */
> > +#define MTK_UART_SAMPLE_POINT	0x0b	/* Sample point register */
> 
> Rename looks good to me. But I'd prefer to have it in a separate patch.
> 
OK.

> >  #define MTK_UART_RATE_FIX	0x0d	/* UART Rate Fix Register */
> > -
> >  #define MTK_UART_DMA_EN		0x13	/* DMA Enable register */
> > +#define MTK_UART_RXTRI_AD	0x14	/* RX Trigger address */
> > +#define MTK_UART_FRACDIV_L	0x15	/* Fractional divider LSB address */
> > +#define MTK_UART_FRACDIV_M	0x16	/* Fractional divider MSB address */
> >  #define MTK_UART_DMA_EN_TX	0x2
> >  #define MTK_UART_DMA_EN_RX	0x5
> >  
> > @@ -46,6 +48,7 @@ enum dma_rx_status {
> >  struct mtk8250_data {
> >  	int			line;
> >  	unsigned int		rx_pos;
> > +	unsigned int		clk_count;
> 
> What is that for, not used in this patch.
> 
It's for other patch. Sorry, I will remove it.

> >  	struct clk		*uart_clk;
> >  	struct clk		*bus_clk;
> >  	struct uart_8250_dma	*dma;
> > @@ -196,9 +199,15 @@ static void mtk8250_shutdown(struct uart_port *port)
> >  mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
> >  			struct ktermios *old)
> >  {
> > +	unsigned short fraction_L_mapping[] = {
> > +		0, 1, 0x5, 0x15, 0x55, 0x57, 0x57, 0x77, 0x7F, 0xFF, 0xFF
> > +	};
> > +	unsigned short fraction_M_mapping[] = {
> > +		0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 3
> > +	};
> >  	struct uart_8250_port *up = up_to_u8250p(port);
> > +	unsigned int baud, quot, fraction;
> >  	unsigned long flags;
> > -	unsigned int baud, quot;
> >  
> >  #ifdef CONFIG_SERIAL_8250_DMA
> >  	if (up->dma) {
> > @@ -214,7 +223,7 @@ static void mtk8250_shutdown(struct uart_port *port)
> >  	serial8250_do_set_termios(port, termios, old);
> >  
> >  	/*
> > -	 * Mediatek UARTs use an extra highspeed register (UART_MTK_HIGHS)
> > +	 * Mediatek UARTs use an extra highspeed register (MTK_UART_HIGHS)
> >  	 *
> >  	 * We need to recalcualte the quot register, as the claculation depends
> >  	 * on the vaule in the highspeed register.
> > @@ -230,18 +239,11 @@ static void mtk8250_shutdown(struct uart_port *port)
> >  				  port->uartclk / 16 / UART_DIV_MAX,
> >  				  port->uartclk);
> >  
> > -	if (baud <= 115200) {
> > -		serial_port_out(port, UART_MTK_HIGHS, 0x0);
> > +	if (baud < 115200) {
> > +		serial_port_out(port, MTK_UART_HIGHS, 0x0);
> >  		quot = uart_get_divisor(port, baud);
> > -	} else if (baud <= 576000) {
> > -		serial_port_out(port, UART_MTK_HIGHS, 0x2);
> > -
> > -		/* Set to next lower baudrate supported */
> > -		if ((baud == 500000) || (baud == 576000))
> > -			baud = 460800;
> > -		quot = DIV_ROUND_UP(port->uartclk, 4 * baud);
> 
> So we allow now also these baud rates? Then you have to update the comment as well.
> 
Yes.

When clock source is different, data sometimes is error by the previous
algorithm. It's not good. So we update new method to fix the issue.


> Regards,
> Matthias
> 
> >  	} else {
> > -		serial_port_out(port, UART_MTK_HIGHS, 0x3);
> > +		serial_port_out(port, MTK_UART_HIGHS, 0x3);
> >  		quot = DIV_ROUND_UP(port->uartclk, 256 * baud);
> >  	}
> >  
> > @@ -258,17 +260,29 @@ static void mtk8250_shutdown(struct uart_port *port)
> >  	/* reset DLAB */
> >  	serial_port_out(port, UART_LCR, up->lcr);
> >  
> > -	if (baud > 460800) {
> > +	if (baud >= 115200) {
> >  		unsigned int tmp;
> >  
> > -		tmp = DIV_ROUND_CLOSEST(port->uartclk, quot * baud);
> > -		serial_port_out(port, UART_MTK_SAMPLE_COUNT, tmp - 1);
> > -		serial_port_out(port, UART_MTK_SAMPLE_POINT,
> > -					(tmp - 2) >> 1);
> > +		tmp = (port->uartclk / (baud *  quot)) - 1;
> > +		serial_port_out(port, MTK_UART_SAMPLE_COUNT, tmp);
> > +		serial_port_out(port, MTK_UART_SAMPLE_POINT,
> > +					(tmp >> 1) - 1);
> > +
> > +		/*count fraction to set fractoin register */
> > +		fraction = ((port->uartclk  * 100) / baud / quot) % 100;
> > +		fraction = DIV_ROUND_CLOSEST(fraction, 10);
> > +		serial_port_out(port, MTK_UART_FRACDIV_L,
> > +						fraction_L_mapping[fraction]);
> > +		serial_port_out(port, MTK_UART_FRACDIV_M,
> > +						fraction_M_mapping[fraction]);
> >  	} else {
> > -		serial_port_out(port, UART_MTK_SAMPLE_COUNT, 0x00);
> > -		serial_port_out(port, UART_MTK_SAMPLE_POINT, 0xff);
> > +		serial_port_out(port, MTK_UART_SAMPLE_COUNT, 0x00);
> > +		serial_port_out(port, MTK_UART_SAMPLE_POINT, 0xff);
> > +		serial_port_out(port, MTK_UART_FRACDIV_L, 0x00);
> > +		serial_port_out(port, MTK_UART_FRACDIV_M, 0x00);
> >  	}
> > +	if (uart_console(port))
> > +		up->port.cons->cflag = termios->c_cflag;
> >  
> >  	spin_unlock_irqrestore(&port->lock, flags);
> >  	/* Don't rewrite B0 */
> >
Sean Wang April 28, 2019, 5:40 p.m. UTC | #3 
Hi, Long

I guess you should mean "flow control", not "follow control".
And the commit subject should be swapped between 1/2 and 2/2,
otherwise, the subject is inconsistent with its own content.

       Sean

On Thu, Apr 25, 2019 at 1:41 AM Long Cheng <long.cheng@mediatek.com> wrote:
>
> Add SW and HW follow control function.
>
> Signed-off-by: Long Cheng <long.cheng@mediatek.com>
> ---
>  drivers/tty/serial/8250/8250_mtk.c |   60 ++++++++++++++++++++++--------------
>  1 file changed, 37 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
> index c1fdbc0..959fd85 100644
> --- a/drivers/tty/serial/8250/8250_mtk.c
> +++ b/drivers/tty/serial/8250/8250_mtk.c
> @@ -21,12 +21,14 @@
>
>  #include "8250.h"
>
> -#define UART_MTK_HIGHS         0x09    /* Highspeed register */
> -#define UART_MTK_SAMPLE_COUNT  0x0a    /* Sample count register */
> -#define UART_MTK_SAMPLE_POINT  0x0b    /* Sample point register */
> +#define MTK_UART_HIGHS         0x09    /* Highspeed register */
> +#define MTK_UART_SAMPLE_COUNT  0x0a    /* Sample count register */
> +#define MTK_UART_SAMPLE_POINT  0x0b    /* Sample point register */
>  #define MTK_UART_RATE_FIX      0x0d    /* UART Rate Fix Register */
> -
>  #define MTK_UART_DMA_EN                0x13    /* DMA Enable register */
> +#define MTK_UART_RXTRI_AD      0x14    /* RX Trigger address */
> +#define MTK_UART_FRACDIV_L     0x15    /* Fractional divider LSB address */
> +#define MTK_UART_FRACDIV_M     0x16    /* Fractional divider MSB address */
>  #define MTK_UART_DMA_EN_TX     0x2
>  #define MTK_UART_DMA_EN_RX     0x5
>
> @@ -46,6 +48,7 @@ enum dma_rx_status {
>  struct mtk8250_data {
>         int                     line;
>         unsigned int            rx_pos;
> +       unsigned int            clk_count;
>         struct clk              *uart_clk;
>         struct clk              *bus_clk;
>         struct uart_8250_dma    *dma;
> @@ -196,9 +199,15 @@ static void mtk8250_shutdown(struct uart_port *port)
>  mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
>                         struct ktermios *old)
>  {
> +       unsigned short fraction_L_mapping[] = {
> +               0, 1, 0x5, 0x15, 0x55, 0x57, 0x57, 0x77, 0x7F, 0xFF, 0xFF
> +       };
> +       unsigned short fraction_M_mapping[] = {
> +               0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 3
> +       };
>         struct uart_8250_port *up = up_to_u8250p(port);
> +       unsigned int baud, quot, fraction;
>         unsigned long flags;
> -       unsigned int baud, quot;
>
>  #ifdef CONFIG_SERIAL_8250_DMA
>         if (up->dma) {
> @@ -214,7 +223,7 @@ static void mtk8250_shutdown(struct uart_port *port)
>         serial8250_do_set_termios(port, termios, old);
>
>         /*
> -        * Mediatek UARTs use an extra highspeed register (UART_MTK_HIGHS)
> +        * Mediatek UARTs use an extra highspeed register (MTK_UART_HIGHS)
>          *
>          * We need to recalcualte the quot register, as the claculation depends
>          * on the vaule in the highspeed register.
> @@ -230,18 +239,11 @@ static void mtk8250_shutdown(struct uart_port *port)
>                                   port->uartclk / 16 / UART_DIV_MAX,
>                                   port->uartclk);
>
> -       if (baud <= 115200) {
> -               serial_port_out(port, UART_MTK_HIGHS, 0x0);
> +       if (baud < 115200) {
> +               serial_port_out(port, MTK_UART_HIGHS, 0x0);
>                 quot = uart_get_divisor(port, baud);
> -       } else if (baud <= 576000) {
> -               serial_port_out(port, UART_MTK_HIGHS, 0x2);
> -
> -               /* Set to next lower baudrate supported */
> -               if ((baud == 500000) || (baud == 576000))
> -                       baud = 460800;
> -               quot = DIV_ROUND_UP(port->uartclk, 4 * baud);
>         } else {
> -               serial_port_out(port, UART_MTK_HIGHS, 0x3);
> +               serial_port_out(port, MTK_UART_HIGHS, 0x3);
>                 quot = DIV_ROUND_UP(port->uartclk, 256 * baud);
>         }
>
> @@ -258,17 +260,29 @@ static void mtk8250_shutdown(struct uart_port *port)
>         /* reset DLAB */
>         serial_port_out(port, UART_LCR, up->lcr);
>
> -       if (baud > 460800) {
> +       if (baud >= 115200) {
>                 unsigned int tmp;
>
> -               tmp = DIV_ROUND_CLOSEST(port->uartclk, quot * baud);
> -               serial_port_out(port, UART_MTK_SAMPLE_COUNT, tmp - 1);
> -               serial_port_out(port, UART_MTK_SAMPLE_POINT,
> -                                       (tmp - 2) >> 1);
> +               tmp = (port->uartclk / (baud *  quot)) - 1;
> +               serial_port_out(port, MTK_UART_SAMPLE_COUNT, tmp);
> +               serial_port_out(port, MTK_UART_SAMPLE_POINT,
> +                                       (tmp >> 1) - 1);
> +
> +               /*count fraction to set fractoin register */
> +               fraction = ((port->uartclk  * 100) / baud / quot) % 100;
> +               fraction = DIV_ROUND_CLOSEST(fraction, 10);
> +               serial_port_out(port, MTK_UART_FRACDIV_L,
> +                                               fraction_L_mapping[fraction]);
> +               serial_port_out(port, MTK_UART_FRACDIV_M,
> +                                               fraction_M_mapping[fraction]);
>         } else {
> -               serial_port_out(port, UART_MTK_SAMPLE_COUNT, 0x00);
> -               serial_port_out(port, UART_MTK_SAMPLE_POINT, 0xff);
> +               serial_port_out(port, MTK_UART_SAMPLE_COUNT, 0x00);
> +               serial_port_out(port, MTK_UART_SAMPLE_POINT, 0xff);
> +               serial_port_out(port, MTK_UART_FRACDIV_L, 0x00);
> +               serial_port_out(port, MTK_UART_FRACDIV_M, 0x00);
>         }
> +       if (uart_console(port))
> +               up->port.cons->cflag = termios->c_cflag;
>
>         spin_unlock_irqrestore(&port->lock, flags);
>         /* Don't rewrite B0 */
> --
> 1.7.9.5
>
>
> _______________________________________________
> Linux-mediatek mailing list
> Linux-mediatek@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-mediatek
diff mbox series

Patch

diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index c1fdbc0..959fd85 100644
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -21,12 +21,14 @@ 
 
 #include "8250.h"
 
-#define UART_MTK_HIGHS		0x09	/* Highspeed register */
-#define UART_MTK_SAMPLE_COUNT	0x0a	/* Sample count register */
-#define UART_MTK_SAMPLE_POINT	0x0b	/* Sample point register */
+#define MTK_UART_HIGHS		0x09	/* Highspeed register */
+#define MTK_UART_SAMPLE_COUNT	0x0a	/* Sample count register */
+#define MTK_UART_SAMPLE_POINT	0x0b	/* Sample point register */
 #define MTK_UART_RATE_FIX	0x0d	/* UART Rate Fix Register */
-
 #define MTK_UART_DMA_EN		0x13	/* DMA Enable register */
+#define MTK_UART_RXTRI_AD	0x14	/* RX Trigger address */
+#define MTK_UART_FRACDIV_L	0x15	/* Fractional divider LSB address */
+#define MTK_UART_FRACDIV_M	0x16	/* Fractional divider MSB address */
 #define MTK_UART_DMA_EN_TX	0x2
 #define MTK_UART_DMA_EN_RX	0x5
 
@@ -46,6 +48,7 @@  enum dma_rx_status {
 struct mtk8250_data {
 	int			line;
 	unsigned int		rx_pos;
+	unsigned int		clk_count;
 	struct clk		*uart_clk;
 	struct clk		*bus_clk;
 	struct uart_8250_dma	*dma;
@@ -196,9 +199,15 @@  static void mtk8250_shutdown(struct uart_port *port)
 mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
 			struct ktermios *old)
 {
+	unsigned short fraction_L_mapping[] = {
+		0, 1, 0x5, 0x15, 0x55, 0x57, 0x57, 0x77, 0x7F, 0xFF, 0xFF
+	};
+	unsigned short fraction_M_mapping[] = {
+		0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 3
+	};
 	struct uart_8250_port *up = up_to_u8250p(port);
+	unsigned int baud, quot, fraction;
 	unsigned long flags;
-	unsigned int baud, quot;
 
 #ifdef CONFIG_SERIAL_8250_DMA
 	if (up->dma) {
@@ -214,7 +223,7 @@  static void mtk8250_shutdown(struct uart_port *port)
 	serial8250_do_set_termios(port, termios, old);
 
 	/*
-	 * Mediatek UARTs use an extra highspeed register (UART_MTK_HIGHS)
+	 * Mediatek UARTs use an extra highspeed register (MTK_UART_HIGHS)
 	 *
 	 * We need to recalcualte the quot register, as the claculation depends
 	 * on the vaule in the highspeed register.
@@ -230,18 +239,11 @@  static void mtk8250_shutdown(struct uart_port *port)
 				  port->uartclk / 16 / UART_DIV_MAX,
 				  port->uartclk);
 
-	if (baud <= 115200) {
-		serial_port_out(port, UART_MTK_HIGHS, 0x0);
+	if (baud < 115200) {
+		serial_port_out(port, MTK_UART_HIGHS, 0x0);
 		quot = uart_get_divisor(port, baud);
-	} else if (baud <= 576000) {
-		serial_port_out(port, UART_MTK_HIGHS, 0x2);
-
-		/* Set to next lower baudrate supported */
-		if ((baud == 500000) || (baud == 576000))
-			baud = 460800;
-		quot = DIV_ROUND_UP(port->uartclk, 4 * baud);
 	} else {
-		serial_port_out(port, UART_MTK_HIGHS, 0x3);
+		serial_port_out(port, MTK_UART_HIGHS, 0x3);
 		quot = DIV_ROUND_UP(port->uartclk, 256 * baud);
 	}
 
@@ -258,17 +260,29 @@  static void mtk8250_shutdown(struct uart_port *port)
 	/* reset DLAB */
 	serial_port_out(port, UART_LCR, up->lcr);
 
-	if (baud > 460800) {
+	if (baud >= 115200) {
 		unsigned int tmp;
 
-		tmp = DIV_ROUND_CLOSEST(port->uartclk, quot * baud);
-		serial_port_out(port, UART_MTK_SAMPLE_COUNT, tmp - 1);
-		serial_port_out(port, UART_MTK_SAMPLE_POINT,
-					(tmp - 2) >> 1);
+		tmp = (port->uartclk / (baud *  quot)) - 1;
+		serial_port_out(port, MTK_UART_SAMPLE_COUNT, tmp);
+		serial_port_out(port, MTK_UART_SAMPLE_POINT,
+					(tmp >> 1) - 1);
+
+		/*count fraction to set fractoin register */
+		fraction = ((port->uartclk  * 100) / baud / quot) % 100;
+		fraction = DIV_ROUND_CLOSEST(fraction, 10);
+		serial_port_out(port, MTK_UART_FRACDIV_L,
+						fraction_L_mapping[fraction]);
+		serial_port_out(port, MTK_UART_FRACDIV_M,
+						fraction_M_mapping[fraction]);
 	} else {
-		serial_port_out(port, UART_MTK_SAMPLE_COUNT, 0x00);
-		serial_port_out(port, UART_MTK_SAMPLE_POINT, 0xff);
+		serial_port_out(port, MTK_UART_SAMPLE_COUNT, 0x00);
+		serial_port_out(port, MTK_UART_SAMPLE_POINT, 0xff);
+		serial_port_out(port, MTK_UART_FRACDIV_L, 0x00);
+		serial_port_out(port, MTK_UART_FRACDIV_M, 0x00);
 	}
+	if (uart_console(port))
+		up->port.cons->cflag = termios->c_cflag;
 
 	spin_unlock_irqrestore(&port->lock, flags);
 	/* Don't rewrite B0 */