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SubjectRe: [PATCH] opp: Fix dev_pm_opp_set_rate() to not return early
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Quoting Rajendra Nayak (2020-08-10 00:06:19)
> dev_pm_opp_set_rate() can now be called with freq = 0 inorder
> to either drop performance or bandwidth votes or to disable
> regulators on platforms which support them.
> In such cases, a subsequent call to dev_pm_opp_set_rate() with
> the same frequency ends up returning early because 'old_freq == freq'
> Instead make it fall through and put back the dropped performance
> and bandwidth votes and/or enable back the regulators.
>
> Fixes: cd7ea582 ("opp: Make dev_pm_opp_set_rate() handle freq = 0 to drop performance votes")
> Reported-by: Sajida Bhanu <sbhanu@codeaurora.org>
> Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
> ---
> drivers/opp/core.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index 0c8c74a..a994f30 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -901,6 +901,9 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
>
> /* Return early if nothing to do */
> if (old_freq == freq) {
> + if (opp_table->required_opp_tables || opp_table->regulators ||
> + opp_table->paths)
> + goto skip_clk_only;

This is a goto maze! Any chance we can clean this up?

if (!opp_table->required_opp_tables && !opp_table->regulators &&
!opp_table->paths)
if (old_freq == freq) {
ret = 0
dev_dbg(..)
} else if (!_get_opp_count(opp_table)) {
ret = _generic_set_opp_clk_only(dev, clk, freq);
}
} else {
temp_freq = old_freq;
old_opp = _find_freq_ceil(opp_table, &temp_freq);
...
dev_pm_opp_put(opp);
put_old_opp:
if (!IS_ERR(old_opp))
dev_pm_opp_put(old_opp);
}
put_opp_table:
dev_pm_opp_put_opp_table(opp_table);

And that stuff in the else should probably go to another function.

> dev_dbg(dev, "%s: old/new frequencies (%lu Hz) are same, nothing to do\n",
> __func__, freq);
> ret = 0;
> @@ -919,6 +922,7 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
> goto put_opp_table;
> }
>
> +skip_clk_only:
> temp_freq = old_freq;
> old_opp = _find_freq_ceil(opp_table, &temp_freq);
> if (IS_ERR(old_opp)) {
> @@ -954,8 +958,10 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
> IS_ERR(old_opp) ? NULL : old_opp->supplies,
> opp->supplies);
> } else {
> + ret = 0;
> /* Only frequency scaling */
> - ret = _generic_set_opp_clk_only(dev, clk, freq);
> + if (freq != old_freq)
> + ret = _generic_set_opp_clk_only(dev, clk, freq);
> }

And write this as

else if (freq != old_freq) {
ret = _generic_set_opp_clk_only(..)
} else {
ret = 0;
}

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