Re: [PATCH v2] clk: meson: Fix the determine rate error in clk_regmap_divider_ro_ops
From: Chuan Liu
Date: Wed Nov 13 2024 - 01:56:50 EST
On 11/12/2024 9:24 PM, Neil Armstrong wrote:
[ EXTERNAL EMAIL ]
On 12/11/2024 13:57, Chuan Liu via B4 Relay wrote:
From: Chuan Liu <chuan.liu@xxxxxxxxxxx>
The rate determined by calling clk_regmap_divider_ro_ops with
clk_regmap_div_determine_rate is not RO, which will result in the
unexpected modification of the frequency of its children when setting
the rate of a clock that references clk_regmap_divider_ro_ops.
Fiexs: ea11dda9e091 ("clk: meson: add regmap clocks")
Signed-off-by: Chuan Liu <chuan.liu@xxxxxxxxxxx>
---
Background: During the execution of clk_set_rate(), the function
clk_core_round_rate_nolock() is called to calculate the matching rate
and save it to 'core->new_rate'. At the same time, it recalculates and
updates its 'child->newrate'. Finally, clk_change_rate() is called to
set all 'new_rates'.
---
Changes in v2:
- Remove the CLK_DIVIDER_READ_ONLY judgment logic in
clk_regmap_div_determine_rate().
- Add clk_regmap_div_ro_determine_rate().
- Link to v1:
https://lore.kernel.org/r/20241111-fix_childclk_of_roclk_has_been_tampered_with-v1-1-f8c1b6ffdcb0@xxxxxxxxxxx
---
drivers/clk/meson/clk-regmap.c | 36
++++++++++++++++++++----------------
1 file changed, 20 insertions(+), 16 deletions(-)
diff --git a/drivers/clk/meson/clk-regmap.c
b/drivers/clk/meson/clk-regmap.c
index 07f7e441b916..edf65ca92c7a 100644
--- a/drivers/clk/meson/clk-regmap.c
+++ b/drivers/clk/meson/clk-regmap.c
@@ -80,21 +80,6 @@ static int clk_regmap_div_determine_rate(struct
clk_hw *hw,
{
struct clk_regmap *clk = to_clk_regmap(hw);
struct clk_regmap_div_data *div = clk_get_regmap_div_data(clk);
- unsigned int val;
- int ret;
-
- /* if read only, just return current value */
- if (div->flags & CLK_DIVIDER_READ_ONLY) {
You're breaking current code by no more checking this flag,
the new clk_regmap_div_ro_determine_rate() is fine, but you should call
it from here if CLK_DIVIDER_READ_ONLY is set.
My idea is that the newly added clk_regmap_div_ro_determine_rate()
implements the functionality of handling CLK_DIVIDER_READ_ONLY in
clk_regmap_div_determine_rate(). If we still keep the logic for
handling CLK_DIVIDER_READ_ONLY here, it will make
clk_regmap_div_determine_rate() ambiguous and easily confused.
Neil
- ret = regmap_read(clk->map, div->offset, &val);
- if (ret)
- return ret;
-
- val >>= div->shift;
- val &= clk_div_mask(div->width);
-
- return divider_ro_determine_rate(hw, req, div->table,
- div->width,
div->flags, val);
- }
return divider_determine_rate(hw, req, div->table, div->width,
div->flags);
@@ -127,9 +112,28 @@ const struct clk_ops clk_regmap_divider_ops = {
};
EXPORT_SYMBOL_NS_GPL(clk_regmap_divider_ops, CLK_MESON);
+static int clk_regmap_div_ro_determine_rate(struct clk_hw *hw,
+ struct clk_rate_request *req)
+{
+ struct clk_regmap *clk = to_clk_regmap(hw);
+ struct clk_regmap_div_data *div = clk_get_regmap_div_data(clk);
+ unsigned int val;
+ int ret;
+
+ ret = regmap_read(clk->map, div->offset, &val);
+ if (ret)
+ return ret;
+
+ val >>= div->shift;
+ val &= clk_div_mask(div->width);
+
+ return divider_ro_determine_rate(hw, req, div->table, div->width,
+ div->flags, val);
+}
+
const struct clk_ops clk_regmap_divider_ro_ops = {
.recalc_rate = clk_regmap_div_recalc_rate,
- .determine_rate = clk_regmap_div_determine_rate,
+ .determine_rate = clk_regmap_div_ro_determine_rate,
};
EXPORT_SYMBOL_NS_GPL(clk_regmap_divider_ro_ops, CLK_MESON);
---
base-commit: 664988eb47dd2d6ae1d9e4188ec91832562f8f26
change-id:
20241111-fix_childclk_of_roclk_has_been_tampered_with-61dbcc623746
Best regards,