Commit 50359819 authored by Heiko Stuebner's avatar Heiko Stuebner Committed by Stephen Boyd

clk-divider: make sure read-only dividers do not write to their register

Commit e6d5e7d9 ("clk-divider: Fix READ_ONLY when divider > 1") removed
the special ops struct for read-only clocks and instead opted to handle
them inside the regular ops.

On the rk3368 this results in breakage as aclkm now gets set a value.
While it is the same divider value, the A53 core still doesn't like it,
which can result in the cpu ending up in a hang.
The reason being that "ACLKENMasserts one clock cycle before the rising
edge of ACLKM" and the clock should only be touched when STANDBYWFIL2
is asserted.

To fix this, reintroduce the read-only ops but do include the round_rate
callback. That way no writes that may be unsafe are done to the divider
register in any case.

The Rockchip use of the clk_divider_ops is adapted to this split again,
as is the nxp, lpc18xx-ccu driver that was included since the original
commit. On lpc18xx-ccu the divider seems to always be read-only
so only uses the new ops now.

Fixes: e6d5e7d9 ("clk-divider: Fix READ_ONLY when divider > 1")
Reported-by: default avatarZhang Qing <>
Signed-off-by: default avatarHeiko Stuebner <>
Signed-off-by: default avatarStephen Boyd <>
parent eac2d86d
......@@ -423,6 +423,12 @@ const struct clk_ops clk_divider_ops = {
const struct clk_ops clk_divider_ro_ops = {
.recalc_rate = clk_divider_recalc_rate,
.round_rate = clk_divider_round_rate,
static struct clk *_register_divider(struct device *dev, const char *name,
const char *parent_name, unsigned long flags,
void __iomem *reg, u8 shift, u8 width,
......@@ -446,7 +452,10 @@ static struct clk *_register_divider(struct device *dev, const char *name,
return ERR_PTR(-ENOMEM); = name;
init.ops = &clk_divider_ops;
if (clk_divider_flags & CLK_DIVIDER_READ_ONLY)
init.ops = &clk_divider_ro_ops;
init.ops = &clk_divider_ops;
init.flags = flags | CLK_IS_BASIC;
init.parent_names = (parent_name ? &parent_name: NULL);
init.num_parents = (parent_name ? 1 : 0);
......@@ -222,7 +222,7 @@ static void lpc18xx_ccu_register_branch_gate_div(struct lpc18xx_clk_branch *bran
div->width = 1;
div_hw = &div->hw;
div_ops = &clk_divider_ops;
div_ops = &clk_divider_ro_ops;
branch->gate.reg = branch->offset + reg_base;
......@@ -90,7 +90,9 @@ static struct clk *rockchip_clk_register_branch(const char *name,
div->width = div_width;
div->lock = lock;
div->table = div_table;
div_ops = &clk_divider_ops;
div_ops = (div_flags & CLK_DIVIDER_READ_ONLY)
? &clk_divider_ro_ops
: &clk_divider_ops;
clk = clk_register_composite(NULL, name, parent_names, num_parents,
......@@ -385,6 +385,7 @@ struct clk_divider {
extern const struct clk_ops clk_divider_ops;
extern const struct clk_ops clk_divider_ro_ops;
unsigned long divider_recalc_rate(struct clk_hw *hw, unsigned long parent_rate,
unsigned int val, const struct clk_div_table *table,
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment