Hi Samuel,
On 9/29/21 1:42 PM, Samuel Holland wrote:
> Since commit ea572f816032 ("PM / devfreq: Change return type of
> devfreq_set_freq_table()"), all devfreq devices are required to have a
> valid freq_table. If freq_table is not provided by the driver, it will
> be filled in by set_freq_table() from the OPPs; if that fails,
> devfreq_add_device() will return an error.
>
> However, since commit ab8f58ad72c4 ("PM / devfreq: Set min/max_freq when
> adding the devfreq device"), devfreq devices are _also_ required to have
> an OPP table, even if they provide freq_table. devfreq_add_device()
> requires dev_pm_opp_find_freq_ceil() and dev_pm_opp_find_freq_floor() to
> return successfully, specifically to initialize scaling_min/max_freq.
>
> Not all drivers need an OPP table. For example, a driver where all
> frequencies are determined dynamically could work by filling out only
> freq_table. But with the current code it must call dev_pm_opp_add() on
> every freq_table entry to probe successfully.
As you commented, if device has no opp table, it should call dev_pm_opp_add().
The devfreq have to use OPP for controlling the frequency/regulator.
Actually, I want that all devfreq driver uses the OPP as default way.
Are there any reason why don't use the OPP table?
>
> The offending properties, scaling_min/max_freq, are only necessary if a
> device has OPPs; if no OPPs exist at all, OPPs cannot be dynamically
> enabled or disabled, so those values have no effect. Thus it is trivial
> to restore support for devices with freq_table only and not OPPs -- move
> those initializations behind the check for a valid OPP table.
>
> Since get_freq_range() uses scaling_max_freq in a min() expression, it
> must be initialized to the maximum possible value. scaling_min_freq is
> initialized as well for consistency.
>
> Fixes: ab8f58ad72c4 ("PM / devfreq: Set min/max_freq when adding the devfreq device")
> Signed-off-by: Samuel Holland <samuel@xxxxxxxxxxxx>
> ---
> drivers/devfreq/devfreq.c | 36 ++++++++++++++++++++----------------
> 1 file changed, 20 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 7a8b022ba456..426e31e6c448 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -835,24 +835,28 @@ struct devfreq *devfreq_add_device(struct device *dev,
> mutex_lock(&devfreq->lock);
> }
>
> - devfreq->scaling_min_freq = find_available_min_freq(devfreq);
> - if (!devfreq->scaling_min_freq) {
> - mutex_unlock(&devfreq->lock);
> - err = -EINVAL;
> - goto err_dev;
> - }
> -
> - devfreq->scaling_max_freq = find_available_max_freq(devfreq);
> - if (!devfreq->scaling_max_freq) {
> - mutex_unlock(&devfreq->lock);
> - err = -EINVAL;
> - goto err_dev;
> - }
> -
> - devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
> devfreq->opp_table = dev_pm_opp_get_opp_table(dev);
> - if (IS_ERR(devfreq->opp_table))
> + if (IS_ERR(devfreq->opp_table)) {
> devfreq->opp_table = NULL;
> + devfreq->scaling_min_freq = 0;
> + devfreq->scaling_max_freq = ULONG_MAX;
> + } else {
> + devfreq->scaling_min_freq = find_available_min_freq(devfreq);
> + if (!devfreq->scaling_min_freq) {
> + mutex_unlock(&devfreq->lock);
> + err = -EINVAL;
> + goto err_dev;
> + }
> +
> + devfreq->scaling_max_freq = find_available_max_freq(devfreq);
> + if (!devfreq->scaling_max_freq) {
> + mutex_unlock(&devfreq->lock);
> + err = -EINVAL;
> + goto err_dev;
> + }
> +
> + devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
> + }
>
> atomic_set(&devfreq->suspend_count, 0);
>
>
--
Best Regards,
Chanwoo Choi
Samsung Electronics
