diff mbox series

clk: clk-gpio: Add dt option to propagate rate change to parent

Message ID 20191106113551.5557-1-alexandru.ardelean@analog.com (mailing list archive)
State Changes Requested, archived
Headers show
Series clk: clk-gpio: Add dt option to propagate rate change to parent | expand

Commit Message

Alexandru Ardelean Nov. 6, 2019, 11:35 a.m. UTC 
From: Michael Hennerich <michael.hennerich@analog.com>

For certain setups/boards it's useful to propagate the rate change of the
clock up one level to the parent clock.

This change implements this by defining a `clk-set-rate-parent` device-tree
property which sets the `CLK_SET_RATE_PARENT` flag to the clock (when set).

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 drivers/clk/clk-gpio.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Stephen Boyd Nov. 6, 2019, 10:43 p.m. UTC | #1 
Quoting Alexandru Ardelean (2019-11-06 03:35:51)
> From: Michael Hennerich <michael.hennerich@analog.com>
> 
> For certain setups/boards it's useful to propagate the rate change of the
> clock up one level to the parent clock.
> 
> This change implements this by defining a `clk-set-rate-parent` device-tree
> property which sets the `CLK_SET_RATE_PARENT` flag to the clock (when set).
> 
> Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> ---
>  drivers/clk/clk-gpio.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/clk-gpio.c b/drivers/clk/clk-gpio.c
> index 9d930edd6516..6dfbc4b952fe 100644
> --- a/drivers/clk/clk-gpio.c
> +++ b/drivers/clk/clk-gpio.c
> @@ -241,6 +241,7 @@ static int gpio_clk_driver_probe(struct platform_device *pdev)
>         struct device_node *node = pdev->dev.of_node;
>         const char **parent_names, *gpio_name;
>         unsigned int num_parents;
> +       unsigned long clk_flags;
>         struct gpio_desc *gpiod;
>         struct clk *clk;
>         bool is_mux;
> @@ -274,13 +275,16 @@ static int gpio_clk_driver_probe(struct platform_device *pdev)
>                 return ret;
>         }
>  
> +       clk_flags = of_property_read_bool(node, "clk-set-rate-parent") ?
> +                       CLK_SET_RATE_PARENT : 0;

Is there a DT binding update somewhere? It looks like a linux-ism from
the DT perspective. I wonder if we can somehow figure out that it's OK
to call clk_set_rate() on the parent here? Or is it safe to assume that
we can just always call set rate on the parent? I think for a gate it's
good and we can just do so, but for a mux maybe not. Care to describe
your scenario a little more so we can understand why you want to set
this flag? Is it for a mux or a gate type gpio?
Alexandru Ardelean Nov. 7, 2019, 1:25 p.m. UTC | #2 
On Wed, 2019-11-06 at 14:43 -0800, Stephen Boyd wrote:
> Quoting Alexandru Ardelean (2019-11-06 03:35:51)
> > From: Michael Hennerich <michael.hennerich@analog.com>
> > 
> > For certain setups/boards it's useful to propagate the rate change of
> > the
> > clock up one level to the parent clock.
> > 
> > This change implements this by defining a `clk-set-rate-parent` device-
> > tree
> > property which sets the `CLK_SET_RATE_PARENT` flag to the clock (when
> > set).
> > 
> > Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > ---
> >  drivers/clk/clk-gpio.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/clk/clk-gpio.c b/drivers/clk/clk-gpio.c
> > index 9d930edd6516..6dfbc4b952fe 100644
> > --- a/drivers/clk/clk-gpio.c
> > +++ b/drivers/clk/clk-gpio.c
> > @@ -241,6 +241,7 @@ static int gpio_clk_driver_probe(struct
> > platform_device *pdev)
> >         struct device_node *node = pdev->dev.of_node;
> >         const char **parent_names, *gpio_name;
> >         unsigned int num_parents;
> > +       unsigned long clk_flags;
> >         struct gpio_desc *gpiod;
> >         struct clk *clk;
> >         bool is_mux;
> > @@ -274,13 +275,16 @@ static int gpio_clk_driver_probe(struct
> > platform_device *pdev)
> >                 return ret;
> >         }
> >  
> > +       clk_flags = of_property_read_bool(node, "clk-set-rate-parent")
> > ?
> > +                       CLK_SET_RATE_PARENT : 0;
> 
> Is there a DT binding update somewhere? It looks like a linux-ism from

Good point. I did not think about the DT, and I guess I didn't search it
thoroughly enough. Found DT files now.

> the DT perspective. I wonder if we can somehow figure out that it's OK
> to call clk_set_rate() on the parent here? Or is it safe to assume that
> we can just always call set rate on the parent? I think for a gate it's
> good and we can just do so, but for a mux maybe not. Care to describe
> your scenario a little more so we can understand why you want to set
> this flag? Is it for a mux or a gate type gpio?
> 

For our case we are using it here [with a slight name variation in the prop
name]:
https://github.com/analogdevicesinc/linux/blob/master/arch/arm/boot/dts/zynq-adrv9361-z7035.dtsi#L43

And on this board:
https://wiki.analog.com/resources/eval/user-guides/adrv936x_rfsom/user-guide/introduction

It's for a gate-type GPIO.
The clock defined in that DT (ad9361_clkin) is attached to a clock that has
a fixed rate (xo_40mhz_fixed_clk), that can become a variable rate [from an
external source, when it is provided].

Our understanding, is that a GPIO gate clock should propagate the rate
change to the parent clock. The same goes for the GPIO MUX clock.
So, the default mode would be to always set CLK_SET_RATE_PARENT.

But, given that there are users of this driver, such a behavior change
could break other users, so we are using this DT prop.

There seems to be only one user of gpio-mux-clock in
arch/arm64/boot/dts/renesas/ulcb-kf.dtsi

Whereas for gpio-gate-clock, there are multiple users. I can't say whether
this change would break anything for them, or it would be fine.
Alexandru Ardelean Nov. 8, 2019, 6:50 a.m. UTC | #3 
On Thu, 2019-11-07 at 14:53 -0800, Stephen Boyd wrote:
> Quoting Ardelean, Alexandru (2019-11-07 05:25:38)
> > On Wed, 2019-11-06 at 14:43 -0800, Stephen Boyd wrote:
> > > Quoting Alexandru Ardelean (2019-11-06 03:35:51)
> > > > From: Michael Hennerich <michael.hennerich@analog.com>
> > > > 
> > > > For certain setups/boards it's useful to propagate the rate change
> > > > of
> > > > the
> > > > clock up one level to the parent clock.
> > > > 
> > > > This change implements this by defining a `clk-set-rate-parent`
> > > > device-
> > > > tree
> > > > property which sets the `CLK_SET_RATE_PARENT` flag to the clock
> > > > (when
> > > > set).
> > > > 
> > > > Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
> > > > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > > > ---
> > > >  drivers/clk/clk-gpio.c | 8 ++++++--
> > > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/clk/clk-gpio.c b/drivers/clk/clk-gpio.c
> > > > index 9d930edd6516..6dfbc4b952fe 100644
> > > > --- a/drivers/clk/clk-gpio.c
> > > > +++ b/drivers/clk/clk-gpio.c
> > > > @@ -241,6 +241,7 @@ static int gpio_clk_driver_probe(struct
> > > > platform_device *pdev)
> > > >         struct device_node *node = pdev->dev.of_node;
> > > >         const char **parent_names, *gpio_name;
> > > >         unsigned int num_parents;
> > > > +       unsigned long clk_flags;
> > > >         struct gpio_desc *gpiod;
> > > >         struct clk *clk;
> > > >         bool is_mux;
> > > > @@ -274,13 +275,16 @@ static int gpio_clk_driver_probe(struct
> > > > platform_device *pdev)
> > > >                 return ret;
> > > >         }
> > > >  
> > > > +       clk_flags = of_property_read_bool(node, "clk-set-rate-
> > > > parent")
> > > > ?
> > > > +                       CLK_SET_RATE_PARENT : 0;
> > > 
> > > Is there a DT binding update somewhere? It looks like a linux-ism
> > > from
> > 
> > Good point. I did not think about the DT, and I guess I didn't search
> > it
> > thoroughly enough. Found DT files now.
> > 
> > > the DT perspective. I wonder if we can somehow figure out that it's
> > > OK
> > > to call clk_set_rate() on the parent here? Or is it safe to assume
> > > that
> > > we can just always call set rate on the parent? I think for a gate
> > > it's
> > > good and we can just do so, but for a mux maybe not. Care to describe
> > > your scenario a little more so we can understand why you want to set
> > > this flag? Is it for a mux or a gate type gpio?
> > > 
> > 
> > For our case we are using it here [with a slight name variation in the
> > prop
> > name]:
> > https://github.com/analogdevicesinc/linux/blob/master/arch/arm/boot/dts/zynq-adrv9361-z7035.dtsi#L43
> > 
> > And on this board:
> > https://wiki.analog.com/resources/eval/user-guides/adrv936x_rfsom/user-guide/introduction
> > 
> > It's for a gate-type GPIO.
> > The clock defined in that DT (ad9361_clkin) is attached to a clock that
> > has
> > a fixed rate (xo_40mhz_fixed_clk), that can become a variable rate
> > [from an
> > external source, when it is provided].
> > 
> > Our understanding, is that a GPIO gate clock should propagate the rate
> > change to the parent clock. The same goes for the GPIO MUX clock.
> > So, the default mode would be to always set CLK_SET_RATE_PARENT.
> > 
> > But, given that there are users of this driver, such a behavior change
> > could break other users, so we are using this DT prop.
> > 
> > There seems to be only one user of gpio-mux-clock in
> > arch/arm64/boot/dts/renesas/ulcb-kf.dtsi
> > 
> > Whereas for gpio-gate-clock, there are multiple users. I can't say
> > whether
> > this change would break anything for them, or it would be fine.
> 
> I think we can just add CLK_SET_RATE_PARENT for all gpio gate clks then
> and you'll be happy? Care to send that patch and Cc Geert and other
> Renesas maintainers? That avoids any DT property and should be fine for
> anyone as far as I can tell. Maybe the inverse will be desired, but not
> wanting rate to propagate is an edge case that we may want to call out
> explicitly in DT at some point in the future, but shouldn't worry about
> until then.
> 

Will resend, thanks.
Geert is CC-ed here as well [unless there is another Geert].

I'll send a V2 in-reply-to this thread.

Thanks
Alex
Alexandru Ardelean Nov. 8, 2019, 7:10 a.m. UTC | #4 
On Fri, 2019-11-08 at 06:50 +0000, Ardelean, Alexandru wrote:
> [External]
> 
> On Thu, 2019-11-07 at 14:53 -0800, Stephen Boyd wrote:
> > Quoting Ardelean, Alexandru (2019-11-07 05:25:38)
> > > On Wed, 2019-11-06 at 14:43 -0800, Stephen Boyd wrote:
> > > > Quoting Alexandru Ardelean (2019-11-06 03:35:51)
> > > > > From: Michael Hennerich <michael.hennerich@analog.com>
> > > > > 
> > > > > For certain setups/boards it's useful to propagate the rate
> > > > > change
> > > > > of
> > > > > the
> > > > > clock up one level to the parent clock.
> > > > > 
> > > > > This change implements this by defining a `clk-set-rate-parent`
> > > > > device-
> > > > > tree
> > > > > property which sets the `CLK_SET_RATE_PARENT` flag to the clock
> > > > > (when
> > > > > set).
> > > > > 
> > > > > Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
> > > > > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > > > > ---
> > > > >  drivers/clk/clk-gpio.c | 8 ++++++--
> > > > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/clk/clk-gpio.c b/drivers/clk/clk-gpio.c
> > > > > index 9d930edd6516..6dfbc4b952fe 100644
> > > > > --- a/drivers/clk/clk-gpio.c
> > > > > +++ b/drivers/clk/clk-gpio.c
> > > > > @@ -241,6 +241,7 @@ static int gpio_clk_driver_probe(struct
> > > > > platform_device *pdev)
> > > > >         struct device_node *node = pdev->dev.of_node;
> > > > >         const char **parent_names, *gpio_name;
> > > > >         unsigned int num_parents;
> > > > > +       unsigned long clk_flags;
> > > > >         struct gpio_desc *gpiod;
> > > > >         struct clk *clk;
> > > > >         bool is_mux;
> > > > > @@ -274,13 +275,16 @@ static int gpio_clk_driver_probe(struct
> > > > > platform_device *pdev)
> > > > >                 return ret;
> > > > >         }
> > > > >  
> > > > > +       clk_flags = of_property_read_bool(node, "clk-set-rate-
> > > > > parent")
> > > > > ?
> > > > > +                       CLK_SET_RATE_PARENT : 0;
> > > > 
> > > > Is there a DT binding update somewhere? It looks like a linux-ism
> > > > from
> > > 
> > > Good point. I did not think about the DT, and I guess I didn't search
> > > it
> > > thoroughly enough. Found DT files now.
> > > 
> > > > the DT perspective. I wonder if we can somehow figure out that it's
> > > > OK
> > > > to call clk_set_rate() on the parent here? Or is it safe to assume
> > > > that
> > > > we can just always call set rate on the parent? I think for a gate
> > > > it's
> > > > good and we can just do so, but for a mux maybe not. Care to
> > > > describe
> > > > your scenario a little more so we can understand why you want to
> > > > set
> > > > this flag? Is it for a mux or a gate type gpio?
> > > > 
> > > 
> > > For our case we are using it here [with a slight name variation in
> > > the
> > > prop
> > > name]:
> > > https://github.com/analogdevicesinc/linux/blob/master/arch/arm/boot/dts/zynq-adrv9361-z7035.dtsi#L43
> > > 
> > > And on this board:
> > > https://wiki.analog.com/resources/eval/user-guides/adrv936x_rfsom/user-guide/introduction
> > > 
> > > It's for a gate-type GPIO.
> > > The clock defined in that DT (ad9361_clkin) is attached to a clock
> > > that
> > > has
> > > a fixed rate (xo_40mhz_fixed_clk), that can become a variable rate
> > > [from an
> > > external source, when it is provided].
> > > 
> > > Our understanding, is that a GPIO gate clock should propagate the
> > > rate
> > > change to the parent clock. The same goes for the GPIO MUX clock.
> > > So, the default mode would be to always set CLK_SET_RATE_PARENT.
> > > 
> > > But, given that there are users of this driver, such a behavior
> > > change
> > > could break other users, so we are using this DT prop.
> > > 
> > > There seems to be only one user of gpio-mux-clock in
> > > arch/arm64/boot/dts/renesas/ulcb-kf.dtsi
> > > 
> > > Whereas for gpio-gate-clock, there are multiple users. I can't say
> > > whether
> > > this change would break anything for them, or it would be fine.
> > 
> > I think we can just add CLK_SET_RATE_PARENT for all gpio gate clks then
> > and you'll be happy? Care to send that patch and Cc Geert and other
> > Renesas maintainers? That avoids any DT property and should be fine for
> > anyone as far as I can tell. Maybe the inverse will be desired, but not
> > wanting rate to propagate is an edge case that we may want to call out
> > explicitly in DT at some point in the future, but shouldn't worry about
> > until then.
> > 
> 
> Will resend, thanks.
> Geert is CC-ed here as well [unless there is another Geert].

Oh right.
You CC-ed Geert this time. I assumed that I did, from the get_maintainers
script. It's still seems like black-art trying to see how tag people when
sending patches. Especially if you're new.

> 
> I'll send a V2 in-reply-to this thread.
> 
> Thanks
> Alex
diff mbox series

Patch

diff --git a/drivers/clk/clk-gpio.c b/drivers/clk/clk-gpio.c
index 9d930edd6516..6dfbc4b952fe 100644
--- a/drivers/clk/clk-gpio.c
+++ b/drivers/clk/clk-gpio.c
@@ -241,6 +241,7 @@  static int gpio_clk_driver_probe(struct platform_device *pdev)
 	struct device_node *node = pdev->dev.of_node;
 	const char **parent_names, *gpio_name;
 	unsigned int num_parents;
+	unsigned long clk_flags;
 	struct gpio_desc *gpiod;
 	struct clk *clk;
 	bool is_mux;
@@ -274,13 +275,16 @@  static int gpio_clk_driver_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	clk_flags = of_property_read_bool(node, "clk-set-rate-parent") ?
+			CLK_SET_RATE_PARENT : 0;
+
 	if (is_mux)
 		clk = clk_register_gpio_mux(&pdev->dev, node->name,
-				parent_names, num_parents, gpiod, 0);
+				parent_names, num_parents, gpiod, clk_flags);
 	else
 		clk = clk_register_gpio_gate(&pdev->dev, node->name,
 				parent_names ?  parent_names[0] : NULL, gpiod,
-				0);
+				clk_flags);
 	if (IS_ERR(clk))
 		return PTR_ERR(clk);