[PATCH v6 18/28] clk: Move clk_core_init_rate_req() from clk_core_round_rate_nolock() to its caller

Maxime Ripard
2022-07-11T15:25:05Z

The clk_rate_request structure is used internally as an argument for
the clk_core_determine_round_nolock() and clk_core_round_rate_nolock().

In both cases, the clk_core_init_rate_req() function is used to
initialize the clk_rate_request structure.

However, the expectation on who gets to call that function is
inconsistent between those two functions. Indeed,
clk_core_determine_round_nolock() will assume the structure is properly
initialized and will just use it.

On the other hand, clk_core_round_rate_nolock() will call
clk_core_init_rate_req() itself, expecting the caller to have filled
only a minimal set of parameters (rate, min_rate and max_rate).

If we ignore the calling convention inconsistency, this leads to a
second inconsistency for drivers:

* If they get called by the framework through
clk_core_round_rate_nolock(), the rate, min_rate and max_rate
fields will be filled by the caller, and the best_parent_rate and
best_parent_hw fields will get filled by clk_core_init_rate_req().

* If they get called by a driver through __clk_determine_rate (and
thus clk_core_round_rate_nolock), only best_parent_rate and
best_parent_hw are being explicitly set by the framework. Even
though we can reasonably expect rate to be set, only one of the 6
in-tree users explicitly set min_rate and max_rate.

* If they get called by the framework through
clk_core_determine_round_nolock(), then we have two callpaths.
Either it will be called by clk_core_round_rate_nolock() itself, or
it will be called by clk_calc_new_rates(), which will properly
initialize rate, min_rate, max_rate itself, and best_parent_rate
and best_parent_hw through clk_core_init_rate_req().

Even though the first and third case seems equivalent, they aren't when
the clock has CLK_SET_RATE_PARENT. Indeed, in such a case
clk_core_round_rate_nolock() will call itself on the current parent
clock with the same clk_rate_request structure.

The clk_core_init_rate_req() function will then be called on the parent
clock, with the child clk_rate_request pointer and will fill the
best_parent_rate and best_parent_hw fields with the parent context.

When the whole recursion stops and the call returns, the initial caller
will end up with a clk_rate_request structure with some informations of
the child clock (rate, min_rate, max_rate) and some others of the last
clock up the tree whose child had CLK_SET_RATE_PARENT (best_parent_hw,
best_parent_rate).

In the most common case, best_parent_rate is going to be equal on all
the parent clocks so it's not a big deal. However, best_parent_hw is
going to point to a clock that never has been a valid parent for that
clock which is definitely confusing.

In order to fix the calling inconsistency, let's move the
clk_core_init_rate_req() calls to the callers, which will also help a
bit with the clk_core_round_rate_nolock() recursion.

Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com> # imx8mp
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> # exynos4210, meson g12b
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
drivers/clk/clk.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 6670e61edb31..7a071c567800 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1415,8 +1415,6 @@ static int clk_core_round_rate_nolock(struct clk_core *core,
return 0;
}

- clk_core_init_rate_req(core, req, req->rate);
-
if (clk_core_can_round(core))
return clk_core_determine_round_nolock(core, req);
else if (core->flags & CLK_SET_RATE_PARENT)
@@ -1464,8 +1462,8 @@ unsigned long clk_hw_round_rate(struct clk_hw *hw, unsigned long rate)
int ret;
struct clk_rate_request req;

+ clk_core_init_rate_req(hw->core, &req, rate);
clk_core_get_boundaries(hw->core, &req.min_rate, &req.max_rate);
- req.rate = rate;

ret = clk_core_round_rate_nolock(hw->core, &req);
if (ret)
@@ -1497,8 +1495,8 @@ long clk_round_rate(struct clk *clk, unsigned long rate)
if (clk->exclusive_count)
clk_core_rate_unprotect(clk->core);

+ clk_core_init_rate_req(clk->core, &req, rate);
clk_core_get_boundaries(clk->core, &req.min_rate, &req.max_rate);
- req.rate = rate;

ret = clk_core_round_rate_nolock(clk->core, &req);

@@ -2206,8 +2204,8 @@ static unsigned long clk_core_req_round_rate_nolock(struct clk_core *core,
if (cnt < 0)
return cnt;

+ clk_core_init_rate_req(core, &req, req_rate);
clk_core_get_boundaries(core, &req.min_rate, &req.max_rate);
- req.rate = req_rate;

ret = clk_core_round_rate_nolock(core, &req);

--
2.36.1