[PATCH] clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag

[PATCH] clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag

[Soren Brinkmann]

Dividers which have CLK_DIVIDER_ONE_BASED set have a redundant state,
being a divider value of zero. Some hardware implementations allow a
zero divider which simply doesn't alter the frequency. I.e. it acts like
a divide by one or bypassing the divider.
This flag is used to handle such HW in the clk-divider model.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
---
 drivers/clk/clk-divider.c    | 5 +++--
 include/linux/clk-provider.h | 8 +++++++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 68b4021..6d96741 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -109,8 +109,9 @@ static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
 
 	div = _get_div(divider, val);
 	if (!div) {
-		WARN(1, "%s: Invalid divisor for clock %s\n", __func__,
-						__clk_get_name(hw->clk));
+		WARN(!(divider->flags & CLK_DIVIDER_ALLOW_ZERO),
+			"%s: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set\n",
+			__clk_get_name(hw->clk));
 		return parent_rate;
 	}
 
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 7f197d7..811426d 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -239,9 +239,14 @@ struct clk_div_table {
  * CLK_DIVIDER_ONE_BASED - by default the divisor is the value read from the
  * 	register plus one.  If CLK_DIVIDER_ONE_BASED is set then the divider is
  * 	the raw value read from the register, with the value of zero considered
- * 	invalid
+ *	invalid, unless CLK_DIVIDER_ALLOW_ZERO is set.
  * CLK_DIVIDER_POWER_OF_TWO - clock divisor is 2 raised to the value read from
  * 	the hardware register
+ * CLK_DIVIDER_ALLOW_ZERO - Allow zero divisors.  For dividers which have
+ *	CLK_DIVIDER_ONE_BASED set, it is possible to end up with a zero divisor.
+ *	Some hardware implementations gracefully handle this case and allow a
+ *	zero divisor by not modifying their input clock
+ *	(divide by one / bypass).
  */
 struct clk_divider {
 	struct clk_hw	hw;
@@ -255,6 +260,7 @@ struct clk_divider {
 
 #define CLK_DIVIDER_ONE_BASED		BIT(0)
 #define CLK_DIVIDER_POWER_OF_TWO	BIT(1)
+#define CLK_DIVIDER_ALLOW_ZERO		BIT(2)
 
 extern const struct clk_ops clk_divider_ops;
 struct clk *clk_register_divider(struct device *dev, const char *name,
-- 
1.8.2

[PATCH] clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag

[Mike Turquette]

Quoting Soren Brinkmann (2013-04-02 15:36:56)
> Dividers which have CLK_DIVIDER_ONE_BASED set have a redundant state,
> being a divider value of zero. Some hardware implementations allow a
> zero divider which simply doesn't alter the frequency. I.e. it acts like
> a divide by one or bypassing the divider.
> This flag is used to handle such HW in the clk-divider model.
> 
> Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>

This version looks good.  Taken into clk-next.

Thanks,
Mike

> ---
>  drivers/clk/clk-divider.c    | 5 +++--
>  include/linux/clk-provider.h | 8 +++++++-
>  2 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> index 68b4021..6d96741 100644
> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c
> @@ -109,8 +109,9 @@ static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
>  
>         div = _get_div(divider, val);
>         if (!div) {
> -               WARN(1, "%s: Invalid divisor for clock %s\n", __func__,
> -                                               __clk_get_name(hw->clk));
> +               WARN(!(divider->flags & CLK_DIVIDER_ALLOW_ZERO),
> +                       "%s: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set\n",
> +                       __clk_get_name(hw->clk));
>                 return parent_rate;
>         }
>  
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 7f197d7..811426d 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -239,9 +239,14 @@ struct clk_div_table {
>   * CLK_DIVIDER_ONE_BASED - by default the divisor is the value read from the
>   *     register plus one.  If CLK_DIVIDER_ONE_BASED is set then the divider is
>   *     the raw value read from the register, with the value of zero considered
> - *     invalid
> + *     invalid, unless CLK_DIVIDER_ALLOW_ZERO is set.
>   * CLK_DIVIDER_POWER_OF_TWO - clock divisor is 2 raised to the value read from
>   *     the hardware register
> + * CLK_DIVIDER_ALLOW_ZERO - Allow zero divisors.  For dividers which have
> + *     CLK_DIVIDER_ONE_BASED set, it is possible to end up with a zero divisor.
> + *     Some hardware implementations gracefully handle this case and allow a
> + *     zero divisor by not modifying their input clock
> + *     (divide by one / bypass).
>   */
>  struct clk_divider {
>         struct clk_hw   hw;
> @@ -255,6 +260,7 @@ struct clk_divider {
>  
>  #define CLK_DIVIDER_ONE_BASED          BIT(0)
>  #define CLK_DIVIDER_POWER_OF_TWO       BIT(1)
> +#define CLK_DIVIDER_ALLOW_ZERO         BIT(2)
>  
>  extern const struct clk_ops clk_divider_ops;
>  struct clk *clk_register_divider(struct device *dev, const char *name,
> -- 
> 1.8.2

[PATCH] clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag

[Sören Brinkmann]

On Wed, Apr 03, 2013 at 08:40:27AM -0700, Mike Turquette wrote:
> Quoting Soren Brinkmann (2013-04-02 15:36:56)
> > Dividers which have CLK_DIVIDER_ONE_BASED set have a redundant state,
> > being a divider value of zero. Some hardware implementations allow a
> > zero divider which simply doesn't alter the frequency. I.e. it acts like
> > a divide by one or bypassing the divider.
> > This flag is used to handle such HW in the clk-divider model.
> > 
> > Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
> 
> This version looks good.  Taken into clk-next.
Thanks.

	S?ren