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 <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
