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Subject[PATCH v3 34/34] clk: change handling of round_rate() such that only zero is an error
Date
Change the handling of clk_ops->round_rate() return values such that only
zero is treated as an error. All implementations of clk_ops->round_rate()
will have previously been updated to match this change.

Using zero as the determinant for an error means its possible to pass an
unsigned long as req->rate to a clk_ops->round_rate() function and return a
rounded clock which is as high as the original req->rate. This allows us on
32 bit systems to return rounded rates of (2^32)-1 Hz or ULONG_MAX Hz -
whereas without this change and the associated clk_ops->round_rate() change
the maximum value that can be returned via clk_ops->round_rate() is
LONG_MAX Hz - after which a higher-frequency clock looks like a negative
error code - due to sign extension.

Signed-off-by: Bryan O'Donoghue <pure.logic@nexus-software.ie>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: linux-clk@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
drivers/clk/clk.c | 15 +++------------
1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 8a1860a..6af2ece 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -909,7 +909,6 @@ static int clk_core_round_rate_nolock(struct clk_core *core,
struct clk_rate_request *req)
{
struct clk_core *parent;
- long rate;

lockdep_assert_held(&prepare_lock);

@@ -928,12 +927,8 @@ static int clk_core_round_rate_nolock(struct clk_core *core,
if (core->ops->determine_rate) {
return core->ops->determine_rate(core->hw, req);
} else if (core->ops->round_rate) {
- rate = core->ops->round_rate(core->hw, req->rate,
+ req->rate = core->ops->round_rate(core->hw, req->rate,
&req->best_parent_rate);
- if (rate < 0)
- return rate;
-
- req->rate = rate;
} else if (core->flags & CLK_SET_RATE_PARENT) {
return clk_core_round_rate_nolock(parent, req);
} else {
@@ -1454,12 +1449,8 @@ static struct clk_core *clk_calc_new_rates(struct clk_core *core,
new_rate = req.rate;
parent = req.best_parent_hw ? req.best_parent_hw->core : NULL;
} else if (core->ops->round_rate) {
- ret = core->ops->round_rate(core->hw, rate,
- &best_parent_rate);
- if (ret < 0)
- return NULL;
-
- new_rate = ret;
+ new_rate = core->ops->round_rate(core->hw, rate,
+ &best_parent_rate);
if (new_rate < min_rate || new_rate > max_rate)
return NULL;
} else if (!parent || !(core->flags & CLK_SET_RATE_PARENT)) {
--
2.7.4
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