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clk: divider: Introduce CLK_DIVIDER_ALLOW_ZERO flag 

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>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
This commit is contained in:
Soren Brinkmann 2013-04-02 15:36:56 -07:00 committed by Mike Turquette
parent f640c0fad6
commit 056b205316
2 changed files with 10 additions and 3 deletions
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5
drivers/clk/clk-divider.c
View File

@ -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;
}

8
include/linux/clk-provider.h
View File

@ -249,9 +249,14 @@ 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;
@ -265,6 +270,7 @@ 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,