* [PATCH] clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag
@ 2013-04-02 22:36 ` Soren Brinkmann
0 siblings, 0 replies; 5+ messages in thread
From: Soren Brinkmann @ 2013-04-02 22:36 UTC (permalink / raw)
To: Mike Turquette
Cc: Shawn Guo, Rajendra Nayak, Andrew Lunn, James Hogan,
linux-arm-kernel, linux-kernel, 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
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH] clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag
@ 2013-04-02 22:36 ` Soren Brinkmann
0 siblings, 0 replies; 5+ messages in thread
From: Soren Brinkmann @ 2013-04-02 22:36 UTC (permalink / raw)
To: linux-arm-kernel
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
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH] clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag
2013-04-02 22:36 ` Soren Brinkmann
(?)
@ 2013-04-03 15:40 ` Mike Turquette
2013-04-03 16:31 ` Sören Brinkmann
-1 siblings, 1 reply; 5+ messages in thread
From: Mike Turquette @ 2013-04-03 15:40 UTC (permalink / raw)
To: linux-arm-kernel
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
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag
2013-04-03 15:40 ` Mike Turquette
@ 2013-04-03 16:31 ` Sören Brinkmann
0 siblings, 0 replies; 5+ messages in thread
From: Sören Brinkmann @ 2013-04-03 16:31 UTC (permalink / raw)
To: Mike Turquette
Cc: Shawn Guo, Rajendra Nayak, Andrew Lunn, James Hogan,
linux-arm-kernel, linux-kernel
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.
Sören
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag
@ 2013-04-03 16:31 ` Sören Brinkmann
0 siblings, 0 replies; 5+ messages in thread
From: Sören Brinkmann @ 2013-04-03 16:31 UTC (permalink / raw)
To: linux-arm-kernel
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
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2013-04-03 16:31 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2013-04-02 22:36 [PATCH] clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag Soren Brinkmann
2013-04-02 22:36 ` Soren Brinkmann
2013-04-03 15:40 ` Mike Turquette
2013-04-03 16:31 ` Sören Brinkmann
2013-04-03 16:31 ` Sören Brinkmann
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