Re: [PATCH v1] opp: Release current OPP properly

Viresh Kumar
2021-08-13T04:12:32Z

On 12-08-21, 13:13, Dmitry Osipenko wrote:
> The current_opp is released only when whole OPP table is released,
> otherwise it's only marked as removed by dev_pm_opp_remove_table().
> Functions like dev_pm_opp_put_clkname() and dev_pm_opp_put_supported_hw()
> are checking whether OPP table is empty and it's not if current_opp is
> set since it holds the refcount of OPP, this produces a noisy warning
> from these functions about busy OPP table. Release current_opp when
> OPP table is removed to fix it.
>
> Cc: stable@vger.kernel.org
> Fixes: 81c4d8a3c414 ("opp: Keep track of currently programmed OPP")
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> drivers/opp/core.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index b335c077f215..73da968b5c86 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -1378,9 +1378,6 @@ static void _opp_table_kref_release(struct kref *kref)
> list_del(&opp_table->node);
> mutex_unlock(&opp_table_lock);
>
> - if (opp_table->current_opp)
> - dev_pm_opp_put(opp_table->current_opp);
> -
> _of_clear_opp_table(opp_table);
>
> /* Release clk */
> @@ -2901,6 +2898,12 @@ void dev_pm_opp_remove_table(struct device *dev)
> if (_opp_remove_all_static(opp_table))
> dev_pm_opp_put_opp_table(opp_table);
>
> + /* Drop reference taken by _find_current_opp() */
> + if (opp_table->current_opp) {
> + dev_pm_opp_put(opp_table->current_opp);
> + opp_table->current_opp = NULL;
> + }
> +

It is better to drop the reference when the OPP table is really
getting removed.

I think the WARN_ON() in the put_* functions can be dropped. It is
important to check this when the stuff is getting set, like in
dev_pm_opp_set_supported_hw(), but removal is just fine.

--
viresh