linux-kernel - Re: [PATCH v3] soc: qcom: rpmhpd: Make power

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Date:   Tue, 19 Oct 2021 16:06:27 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Andy Gross <agross@...nel.org>, Stephen Boyd <swboyd@...omium.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] soc: qcom: rpmhpd: Make power_on actually enable the domain

On Tue, 5 Oct 2021 at 05:35, Bjorn Andersson <bjorn.andersson@...aro.org> wrote:
>
> The general expectation is that powering on a power-domain should make
> the power domain deliver some power, and if a specific performance state
> is needed further requests has to be made.
>
> But in contrast with other power-domain implementations (e.g. rpmpd) the
> RPMh does not have an interface to enable the power, so the driver has
> to vote for a particular corner (performance level) in rpmh_power_on().
>
> But the corner is never initialized, so a typical request to simply
> enable the power domain would not actually turn on the hardware. Further
> more, when no more clients vote for a performance state (i.e. the
> aggregated vote is 0) the power domain would be turned off.
>
> Fix both of these issues by always voting for a corner with non-zero
> value, when the power domain is enabled.
>
> The tracking of the lowest non-zero corner is performed to handle the
> corner case if there's ever a domain with a non-zero lowest corner, in
> which case both rpmh_power_on() and rpmh_rpmhpd_set_performance_state()
> would be allowed to use this lowest corner.
>
> Fixes: 279b7e8a62cc ("soc: qcom: rpmhpd: Add RPMh power domain driver")
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>

Looks reasonable to me!

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Kind regards
Uffe

> ---
>
> Changes since v2:
> - Fixed two spelling mistakes in the commit message
> - Changed the last hunk to search for first non-zero level, rather than the
>   first non-zero index (i.e. 1)
>
>  drivers/soc/qcom/rpmhpd.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/soc/qcom/rpmhpd.c b/drivers/soc/qcom/rpmhpd.c
> index e280a8194725..0ca77ed22c6c 100644
> --- a/drivers/soc/qcom/rpmhpd.c
> +++ b/drivers/soc/qcom/rpmhpd.c
> @@ -30,6 +30,7 @@
>   * @active_only:       True if it represents an Active only peer
>   * @corner:            current corner
>   * @active_corner:     current active corner
> + * @enable_corner:     lowest non-zero corner
>   * @level:             An array of level (vlvl) to corner (hlvl) mappings
>   *                     derived from cmd-db
>   * @level_count:       Number of levels supported by the power domain. max
> @@ -47,6 +48,7 @@ struct rpmhpd {
>         const bool      active_only;
>         unsigned int    corner;
>         unsigned int    active_corner;
> +       unsigned int    enable_corner;
>         u32             level[RPMH_ARC_MAX_LEVELS];
>         size_t          level_count;
>         bool            enabled;
> @@ -401,13 +403,13 @@ static int rpmhpd_aggregate_corner(struct rpmhpd *pd, unsigned int corner)
>  static int rpmhpd_power_on(struct generic_pm_domain *domain)
>  {
>         struct rpmhpd *pd = domain_to_rpmhpd(domain);
> -       int ret = 0;
> +       unsigned int corner;
> +       int ret;
>
>         mutex_lock(&rpmhpd_lock);
>
> -       if (pd->corner)
> -               ret = rpmhpd_aggregate_corner(pd, pd->corner);
> -
> +       corner = max(pd->corner, pd->enable_corner);
> +       ret = rpmhpd_aggregate_corner(pd, corner);
>         if (!ret)
>                 pd->enabled = true;
>
> @@ -452,6 +454,10 @@ static int rpmhpd_set_performance_state(struct generic_pm_domain *domain,
>                 i--;
>
>         if (pd->enabled) {
> +               /* Ensure that the domain isn't turn off */
> +               if (i < pd->enable_corner)
> +                       i = pd->enable_corner;
> +
>                 ret = rpmhpd_aggregate_corner(pd, i);
>                 if (ret)
>                         goto out;
> @@ -488,6 +494,10 @@ static int rpmhpd_update_level_mapping(struct rpmhpd *rpmhpd)
>         for (i = 0; i < rpmhpd->level_count; i++) {
>                 rpmhpd->level[i] = buf[i];
>
> +               /* Remember the first corner with non-zero level */
> +               if (!rpmhpd->level[rpmhpd->enable_corner] && rpmhpd->level[i])
> +                       rpmhpd->enable_corner = i;
> +
>                 /*
>                  * The AUX data may be zero padded.  These 0 valued entries at
>                  * the end of the map must be ignored.
> --
> 2.29.2
>