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[v2] tty: serial: 8250_mtk: Add support for second clock

Message ID 1430117397-13517-1-git-send-email-s.hauer@pengutronix.de
State New
Headers show

Pull-request

git://git.pengutronix.de/git/sha/linux-2.6.git tags/v4.1-mtk-uart-clk-v2

Message

Sascha Hauer April 27, 2015, 6:49 a.m. UTC
The following changes since commit b787f68c36d49bb1d9236f403813641efa74a031:

  Linux 4.1-rc1 (2015-04-26 17:59:10 -0700)

are available in the git repository at:

  git://git.pengutronix.de/git/sha/linux-2.6.git tags/v4.1-mtk-uart-clk-v2

for you to fetch changes up to 02e3f747bea47f6c02dc3f52e40869ea8ce5342a:

  tty: serial: 8250_mtk: Add support for bus clock (2015-04-27 08:39:06 +0200)

----------------------------------------------------------------
This series adds support for the second clock on the Mediatek UART.
This is necessary for SoCs needing a bus clock to be enabled before
the UART can be accessed.

Changes since v1:
- keep support old binding with unnamed clk
- hopefully clarify commit message
- do not leak in if() with unnecessary braces.

----------------------------------------------------------------
Sascha Hauer (4):
      tty: serial: 8250_mtk: remove unnecessary test
      tty: serial: 8250_mtk: Use devm_clk_get
      tty: serial: 8250_mtk: use pm_runtime callbacks for enabling
      tty: serial: 8250_mtk: Add support for bus clock

 .../devicetree/bindings/serial/mtk-uart.txt        |  12 ++-
 drivers/tty/serial/8250/8250_mtk.c                 | 104 ++++++++++++---------
 2 files changed, 70 insertions(+), 46 deletions(-)

Comments

Matthias Brugger May 4, 2015, 9:32 a.m. UTC | #1
2015-04-27 8:49 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> When the driver has probed successfully the clk pointer is always valid,
> so no need to test for it.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  drivers/tty/serial/8250/8250_mtk.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
>

Acked-by: Matthias Brugger <matthias.bgg@gmail.com>

> diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
> index 7a11fac..1297827 100644
> --- a/drivers/tty/serial/8250/8250_mtk.c
> +++ b/drivers/tty/serial/8250/8250_mtk.c
> @@ -214,10 +214,8 @@ static int mtk8250_remove(struct platform_device *pdev)
>         pm_runtime_get_sync(&pdev->dev);
>
>         serial8250_unregister_port(data->line);
> -       if (!IS_ERR(data->uart_clk)) {
> -               clk_disable_unprepare(data->uart_clk);
> -               clk_put(data->uart_clk);
> -       }
> +       clk_disable_unprepare(data->uart_clk);
> +       clk_put(data->uart_clk);
>
>         pm_runtime_disable(&pdev->dev);
>         pm_runtime_put_noidle(&pdev->dev);
> @@ -249,8 +247,7 @@ static int mtk8250_runtime_suspend(struct device *dev)
>  {
>         struct mtk8250_data *data = dev_get_drvdata(dev);
>
> -       if (!IS_ERR(data->uart_clk))
> -               clk_disable_unprepare(data->uart_clk);
> +       clk_disable_unprepare(data->uart_clk);
>
>         return 0;
>  }
> @@ -259,8 +256,7 @@ static int mtk8250_runtime_resume(struct device *dev)
>  {
>         struct mtk8250_data *data = dev_get_drvdata(dev);
>
> -       if (!IS_ERR(data->uart_clk))
> -               clk_prepare_enable(data->uart_clk);
> +       clk_prepare_enable(data->uart_clk);
>
>         return 0;
>  }
> --
> 2.1.4
>
Matthias Brugger May 4, 2015, 9:36 a.m. UTC | #2
2015-04-27 8:49 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> When a struct device * is present clk_get should be used rather
> than of_clk_get. Use the devm variant of this function to be able to
> drop the clk_put in the error and remove pathes. While at it fix
> a wrong error message.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  drivers/tty/serial/8250/8250_mtk.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)

Acked-by: Matthias Brugger <matthias.bgg@gmail.com>
Matthias Brugger May 4, 2015, 11:05 a.m. UTC | #3
2015-04-27 8:49 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> The pm_runtime callbacks already enable and disable the device.
> Use them in probe() and remove() instead of duplicating the
> code. This allows us to concentrate more code for enabling/disabling
> the UART in a single place.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  drivers/tty/serial/8250/8250_mtk.c | 69 ++++++++++++++++++++------------------
>  1 file changed, 36 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
> index bcfaa8dc..2f28bd0 100644
> --- a/drivers/tty/serial/8250/8250_mtk.c
> +++ b/drivers/tty/serial/8250/8250_mtk.c
> @@ -115,6 +115,29 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
>                 tty_termios_encode_baud_rate(termios, baud, baud);
>  }
>
> +static int mtk8250_runtime_suspend(struct device *dev)
> +{
> +       struct mtk8250_data *data = dev_get_drvdata(dev);
> +
> +       clk_disable_unprepare(data->uart_clk);
> +
> +       return 0;
> +}
> +
> +static int mtk8250_runtime_resume(struct device *dev)
> +{
> +       struct mtk8250_data *data = dev_get_drvdata(dev);
> +       int err;
> +
> +       err = clk_prepare_enable(data->uart_clk);
> +       if (err) {
> +               dev_warn(dev, "Can't enable clock\n");
> +               return err;
> +       }
> +
> +       return 0;
> +}
> +
>  static void
>  mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
>  {
> @@ -130,19 +153,12 @@ mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
>  static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
>                            struct mtk8250_data *data)
>  {
> -       int err;
> -
>         data->uart_clk = devm_clk_get(&pdev->dev, NULL);
>         if (IS_ERR(data->uart_clk)) {
>                 dev_warn(&pdev->dev, "Can't get uart clock\n");
>                 return PTR_ERR(data->uart_clk);
>         }
>
> -       err = clk_prepare_enable(data->uart_clk);
> -       if (err) {
> -               dev_warn(&pdev->dev, "Can't prepare clock\n");
> -               return err;
> -       }
>         p->uartclk = clk_get_rate(data->uart_clk);
>
>         return 0;
> @@ -193,14 +209,18 @@ static int mtk8250_probe(struct platform_device *pdev)
>         writel(0x0, uart.port.membase +
>                         (MTK_UART_RATE_FIX << uart.port.regshift));
>
> -       data->line = serial8250_register_8250_port(&uart);
> -       if (data->line < 0)
> -               return data->line;
> -
>         platform_set_drvdata(pdev, data);
>
> -       pm_runtime_set_active(&pdev->dev);
>         pm_runtime_enable(&pdev->dev);
> +       if (!pm_runtime_enabled(&pdev->dev)) {
> +               err = mtk8250_runtime_resume(&pdev->dev);
> +               if (err)
> +                       return err;
> +       }
> +
> +       data->line = serial8250_register_8250_port(&uart);
> +       if (data->line < 0)
> +               return data->line;

Why do you delete pm_runtime_set_active here?
Sascha Hauer May 4, 2015, 12:06 p.m. UTC | #4
On Mon, May 04, 2015 at 01:05:27PM +0200, Matthias Brugger wrote:
> 2015-04-27 8:49 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> > The pm_runtime callbacks already enable and disable the device.
> > Use them in probe() and remove() instead of duplicating the
> > code. This allows us to concentrate more code for enabling/disabling
> > the UART in a single place.
> >
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  drivers/tty/serial/8250/8250_mtk.c | 69 ++++++++++++++++++++------------------
> >  1 file changed, 36 insertions(+), 33 deletions(-)
> >
> > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
> > index bcfaa8dc..2f28bd0 100644
> > --- a/drivers/tty/serial/8250/8250_mtk.c
> > +++ b/drivers/tty/serial/8250/8250_mtk.c
> > @@ -115,6 +115,29 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
> >                 tty_termios_encode_baud_rate(termios, baud, baud);
> >  }
> >
> > +static int mtk8250_runtime_suspend(struct device *dev)
> > +{
> > +       struct mtk8250_data *data = dev_get_drvdata(dev);
> > +
> > +       clk_disable_unprepare(data->uart_clk);
> > +
> > +       return 0;
> > +}
> > +
> > +static int mtk8250_runtime_resume(struct device *dev)
> > +{
> > +       struct mtk8250_data *data = dev_get_drvdata(dev);
> > +       int err;
> > +
> > +       err = clk_prepare_enable(data->uart_clk);
> > +       if (err) {
> > +               dev_warn(dev, "Can't enable clock\n");
> > +               return err;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> >  static void
> >  mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
> >  {
> > @@ -130,19 +153,12 @@ mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
> >  static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
> >                            struct mtk8250_data *data)
> >  {
> > -       int err;
> > -
> >         data->uart_clk = devm_clk_get(&pdev->dev, NULL);
> >         if (IS_ERR(data->uart_clk)) {
> >                 dev_warn(&pdev->dev, "Can't get uart clock\n");
> >                 return PTR_ERR(data->uart_clk);
> >         }
> >
> > -       err = clk_prepare_enable(data->uart_clk);
> > -       if (err) {
> > -               dev_warn(&pdev->dev, "Can't prepare clock\n");
> > -               return err;
> > -       }
> >         p->uartclk = clk_get_rate(data->uart_clk);
> >
> >         return 0;
> > @@ -193,14 +209,18 @@ static int mtk8250_probe(struct platform_device *pdev)
> >         writel(0x0, uart.port.membase +
> >                         (MTK_UART_RATE_FIX << uart.port.regshift));
> >
> > -       data->line = serial8250_register_8250_port(&uart);
> > -       if (data->line < 0)
> > -               return data->line;
> > -
> >         platform_set_drvdata(pdev, data);
> >
> > -       pm_runtime_set_active(&pdev->dev);
> >         pm_runtime_enable(&pdev->dev);
> > +       if (!pm_runtime_enabled(&pdev->dev)) {
> > +               err = mtk8250_runtime_resume(&pdev->dev);
> > +               if (err)
> > +                       return err;
> > +       }
> > +
> > +       data->line = serial8250_register_8250_port(&uart);
> > +       if (data->line < 0)
> > +               return data->line;
> 
> Why do you delete pm_runtime_set_active here?

pm_runtime_set_active() communicates the initial state of the device to
the pm core. Previously the driver activated the device manually by
directly calling clk_prepare_enable(). Since this manual enabling of
the clock is removed in this patch, the device is no longer active,
hence pm_runtime_set_active() has to be removed.

Sascha
Matthias Brugger May 5, 2015, 3:29 p.m. UTC | #5
2015-05-04 14:06 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> On Mon, May 04, 2015 at 01:05:27PM +0200, Matthias Brugger wrote:
>> 2015-04-27 8:49 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
>> > The pm_runtime callbacks already enable and disable the device.
>> > Use them in probe() and remove() instead of duplicating the
>> > code. This allows us to concentrate more code for enabling/disabling
>> > the UART in a single place.
>> >
>> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
>> > ---
>> >  drivers/tty/serial/8250/8250_mtk.c | 69 ++++++++++++++++++++------------------
>> >  1 file changed, 36 insertions(+), 33 deletions(-)
>> >
>> > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
>> > index bcfaa8dc..2f28bd0 100644
>> > --- a/drivers/tty/serial/8250/8250_mtk.c
>> > +++ b/drivers/tty/serial/8250/8250_mtk.c
>> > @@ -115,6 +115,29 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
>> >                 tty_termios_encode_baud_rate(termios, baud, baud);
>> >  }
>> >
>> > +static int mtk8250_runtime_suspend(struct device *dev)
>> > +{
>> > +       struct mtk8250_data *data = dev_get_drvdata(dev);
>> > +
>> > +       clk_disable_unprepare(data->uart_clk);
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +static int mtk8250_runtime_resume(struct device *dev)
>> > +{
>> > +       struct mtk8250_data *data = dev_get_drvdata(dev);
>> > +       int err;
>> > +
>> > +       err = clk_prepare_enable(data->uart_clk);
>> > +       if (err) {
>> > +               dev_warn(dev, "Can't enable clock\n");
>> > +               return err;
>> > +       }
>> > +
>> > +       return 0;
>> > +}
>> > +
>> >  static void
>> >  mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
>> >  {
>> > @@ -130,19 +153,12 @@ mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
>> >  static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
>> >                            struct mtk8250_data *data)
>> >  {
>> > -       int err;
>> > -
>> >         data->uart_clk = devm_clk_get(&pdev->dev, NULL);
>> >         if (IS_ERR(data->uart_clk)) {
>> >                 dev_warn(&pdev->dev, "Can't get uart clock\n");
>> >                 return PTR_ERR(data->uart_clk);
>> >         }
>> >
>> > -       err = clk_prepare_enable(data->uart_clk);
>> > -       if (err) {
>> > -               dev_warn(&pdev->dev, "Can't prepare clock\n");
>> > -               return err;
>> > -       }
>> >         p->uartclk = clk_get_rate(data->uart_clk);
>> >
>> >         return 0;
>> > @@ -193,14 +209,18 @@ static int mtk8250_probe(struct platform_device *pdev)
>> >         writel(0x0, uart.port.membase +
>> >                         (MTK_UART_RATE_FIX << uart.port.regshift));
>> >
>> > -       data->line = serial8250_register_8250_port(&uart);
>> > -       if (data->line < 0)
>> > -               return data->line;
>> > -
>> >         platform_set_drvdata(pdev, data);
>> >
>> > -       pm_runtime_set_active(&pdev->dev);
>> >         pm_runtime_enable(&pdev->dev);
>> > +       if (!pm_runtime_enabled(&pdev->dev)) {
>> > +               err = mtk8250_runtime_resume(&pdev->dev);
>> > +               if (err)
>> > +                       return err;
>> > +       }
>> > +
>> > +       data->line = serial8250_register_8250_port(&uart);
>> > +       if (data->line < 0)
>> > +               return data->line;
>>
>> Why do you delete pm_runtime_set_active here?
>
> pm_runtime_set_active() communicates the initial state of the device to
> the pm core. Previously the driver activated the device manually by
> directly calling clk_prepare_enable(). Since this manual enabling of
> the clock is removed in this patch, the device is no longer active,
> hence pm_runtime_set_active() has to be removed.

Sounds resonable.
Acked-by: Matthias Brugger <matthias.bgg@gmail.com>
Matthias Brugger May 5, 2015, 3:41 p.m. UTC | #6
2015-04-27 8:49 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> The mtk 8250 needs two clocks, one for providing the baudrate and
> one that needs to be enabled for register accesses. The latter has
> not been supported, this patch adds support for it. It is optional
> for now since not all SoCs provide a bus clock.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  .../devicetree/bindings/serial/mtk-uart.txt        | 12 ++++++++--
>  drivers/tty/serial/8250/8250_mtk.c                 | 28 ++++++++++++++++++----
>  2 files changed, 34 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/serial/mtk-uart.txt b/Documentation/devicetree/bindings/serial/mtk-uart.txt
> index 4415226..8d63f1d 100644
> --- a/Documentation/devicetree/bindings/serial/mtk-uart.txt
> +++ b/Documentation/devicetree/bindings/serial/mtk-uart.txt
> @@ -14,7 +14,14 @@ Required properties:
>
>  - interrupts: A single interrupt specifier.
>
> -- clocks: Clock driving the hardware.
> +- clocks : Must contain an entry for each entry in clock-names.
> +  See ../clocks/clock-bindings.txt for details.
> +- clock-names:
> +  - "baud": The clock the baudrate is derived from
> +  - "bus": The bus clock for register accesses (optional)
> +
> +For compatibility with older device trees an unnamed clock is used for the
> +baud clock if the baudclk does not exist. Do not use this for new designs.
>
>  Example:
>
> @@ -22,5 +29,6 @@ Example:
>                 compatible = "mediatek,mt6589-uart", "mediatek,mt6577-uart";
>                 reg = <0x11006000 0x400>;
>                 interrupts = <GIC_SPI 51 IRQ_TYPE_LEVEL_LOW>;
> -               clocks = <&uart_clk>;
> +               clocks = <&uart_clk>, <&bus_clk>;
> +               clock-names = "baud", "bus";
>         };
> diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
> index 2f28bd0..8eb3876 100644
> --- a/drivers/tty/serial/8250/8250_mtk.c
> +++ b/drivers/tty/serial/8250/8250_mtk.c
> @@ -34,6 +34,7 @@
>  struct mtk8250_data {
>         int                     line;
>         struct clk              *uart_clk;
> +       struct clk              *bus_clk;
>  };

Not sure if it would be better to rename the uart_clk to baud_clk
which reflects the new naming scheme.

>
>  static void
> @@ -120,6 +121,7 @@ static int mtk8250_runtime_suspend(struct device *dev)
>         struct mtk8250_data *data = dev_get_drvdata(dev);
>
>         clk_disable_unprepare(data->uart_clk);
> +       clk_disable_unprepare(data->bus_clk);

bus_clk can be NULL.

>
>         return 0;
>  }
> @@ -135,6 +137,12 @@ static int mtk8250_runtime_resume(struct device *dev)
>                 return err;
>         }
>
> +       err = clk_prepare_enable(data->bus_clk);
> +       if (err) {
> +               dev_warn(dev, "Can't enable bus clock\n");
> +               return err;
> +       }
> +

Same here.
Sascha Hauer May 5, 2015, 3:50 p.m. UTC | #7
On Tue, May 05, 2015 at 05:41:16PM +0200, Matthias Brugger wrote:
> 2015-04-27 8:49 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> > The mtk 8250 needs two clocks, one for providing the baudrate and
> > one that needs to be enabled for register accesses. The latter has
> > not been supported, this patch adds support for it. It is optional
> > for now since not all SoCs provide a bus clock.
> >
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  .../devicetree/bindings/serial/mtk-uart.txt        | 12 ++++++++--
> >  drivers/tty/serial/8250/8250_mtk.c                 | 28 ++++++++++++++++++----
> >  2 files changed, 34 insertions(+), 6 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/serial/mtk-uart.txt b/Documentation/devicetree/bindings/serial/mtk-uart.txt
> > index 4415226..8d63f1d 100644
> > --- a/Documentation/devicetree/bindings/serial/mtk-uart.txt
> > +++ b/Documentation/devicetree/bindings/serial/mtk-uart.txt
> > @@ -14,7 +14,14 @@ Required properties:
> >
> >  - interrupts: A single interrupt specifier.
> >
> > -- clocks: Clock driving the hardware.
> > +- clocks : Must contain an entry for each entry in clock-names.
> > +  See ../clocks/clock-bindings.txt for details.
> > +- clock-names:
> > +  - "baud": The clock the baudrate is derived from
> > +  - "bus": The bus clock for register accesses (optional)
> > +
> > +For compatibility with older device trees an unnamed clock is used for the
> > +baud clock if the baudclk does not exist. Do not use this for new designs.
> >
> >  Example:
> >
> > @@ -22,5 +29,6 @@ Example:
> >                 compatible = "mediatek,mt6589-uart", "mediatek,mt6577-uart";
> >                 reg = <0x11006000 0x400>;
> >                 interrupts = <GIC_SPI 51 IRQ_TYPE_LEVEL_LOW>;
> > -               clocks = <&uart_clk>;
> > +               clocks = <&uart_clk>, <&bus_clk>;
> > +               clock-names = "baud", "bus";
> >         };
> > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
> > index 2f28bd0..8eb3876 100644
> > --- a/drivers/tty/serial/8250/8250_mtk.c
> > +++ b/drivers/tty/serial/8250/8250_mtk.c
> > @@ -34,6 +34,7 @@
> >  struct mtk8250_data {
> >         int                     line;
> >         struct clk              *uart_clk;
> > +       struct clk              *bus_clk;
> >  };
> 
> Not sure if it would be better to rename the uart_clk to baud_clk
> which reflects the new naming scheme.

Can do.

> 
> >
> >  static void
> > @@ -120,6 +121,7 @@ static int mtk8250_runtime_suspend(struct device *dev)
> >         struct mtk8250_data *data = dev_get_drvdata(dev);
> >
> >         clk_disable_unprepare(data->uart_clk);
> > +       clk_disable_unprepare(data->bus_clk);
> 
> bus_clk can be NULL.

The clk core handles NULL clks just fine. They are considered dummy
clks. You can prepare/enable them, clk_get_rate of course returns
nothing useful.

Sascha
Matthias Brugger May 8, 2015, 8:59 a.m. UTC | #8
2015-05-05 17:50 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> On Tue, May 05, 2015 at 05:41:16PM +0200, Matthias Brugger wrote:
>> 2015-04-27 8:49 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
>> > The mtk 8250 needs two clocks, one for providing the baudrate and
>> > one that needs to be enabled for register accesses. The latter has
>> > not been supported, this patch adds support for it. It is optional
>> > for now since not all SoCs provide a bus clock.
>> >
>> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
>> > ---
>> >  .../devicetree/bindings/serial/mtk-uart.txt        | 12 ++++++++--
>> >  drivers/tty/serial/8250/8250_mtk.c                 | 28 ++++++++++++++++++----
>> >  2 files changed, 34 insertions(+), 6 deletions(-)
>> >
>> > diff --git a/Documentation/devicetree/bindings/serial/mtk-uart.txt b/Documentation/devicetree/bindings/serial/mtk-uart.txt
>> > index 4415226..8d63f1d 100644
>> > --- a/Documentation/devicetree/bindings/serial/mtk-uart.txt
>> > +++ b/Documentation/devicetree/bindings/serial/mtk-uart.txt
>> > @@ -14,7 +14,14 @@ Required properties:
>> >
>> >  - interrupts: A single interrupt specifier.
>> >
>> > -- clocks: Clock driving the hardware.
>> > +- clocks : Must contain an entry for each entry in clock-names.
>> > +  See ../clocks/clock-bindings.txt for details.
>> > +- clock-names:
>> > +  - "baud": The clock the baudrate is derived from
>> > +  - "bus": The bus clock for register accesses (optional)
>> > +
>> > +For compatibility with older device trees an unnamed clock is used for the
>> > +baud clock if the baudclk does not exist. Do not use this for new designs.
>> >
>> >  Example:
>> >
>> > @@ -22,5 +29,6 @@ Example:
>> >                 compatible = "mediatek,mt6589-uart", "mediatek,mt6577-uart";
>> >                 reg = <0x11006000 0x400>;
>> >                 interrupts = <GIC_SPI 51 IRQ_TYPE_LEVEL_LOW>;
>> > -               clocks = <&uart_clk>;
>> > +               clocks = <&uart_clk>, <&bus_clk>;
>> > +               clock-names = "baud", "bus";
>> >         };
>> > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
>> > index 2f28bd0..8eb3876 100644
>> > --- a/drivers/tty/serial/8250/8250_mtk.c
>> > +++ b/drivers/tty/serial/8250/8250_mtk.c
>> > @@ -34,6 +34,7 @@
>> >  struct mtk8250_data {
>> >         int                     line;
>> >         struct clk              *uart_clk;
>> > +       struct clk              *bus_clk;
>> >  };
>>
>> Not sure if it would be better to rename the uart_clk to baud_clk
>> which reflects the new naming scheme.
>
> Can do.

If you do so you can add:
Acked-by: Matthias Brugger <matthias.bgg@gmail.com>

Thanks,
Matthias