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Date:   Thu, 15 Jul 2021 17:46:02 +0530
From:   Sibi Sankar <sibis@codeaurora.org>
To:     Bjorn Andersson <bjorn.andersson@linaro.org>
Cc:     Andy Gross <agross@kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Rajendra Nayak <rnayak@codeaurora.org>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RESEND PATCH 2/2] soc: qcom: rpmhpd: Make power_on actually
 enable the domain
In-Reply-To: <20210703025449.2687201-1-bjorn.andersson@linaro.org>
References: <20210703025449.2687201-1-bjorn.andersson@linaro.org>
Message-ID: <902f7665ab9045e87fb07f848b994316@codeaurora.org>
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Hey Bjorn,

Thanks for the patch.

On 2021-07-03 08:24, Bjorn Andersson wrote:
> The general expectation is that powering on a power-domain should make
> the power domain deliver some power, and if a specific performace state

s/performace/performance/

> 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 turn 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@linaro.org>
> ---
> 
> Resending because the hunk in rpmhpd_update_level_mapping() was left in 
> the
> index.
> 
>  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 fa209b479ab3..76ea6b053ef0 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;
> @@ -385,13 +387,13 @@ 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;
> 
> @@ -436,6 +438,10 @@ 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;
> @@ -472,6 +478,10 @@ 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 non-zero corner */

Shouldn't we be tracking the corner that
corresponds to the first non-zero level
instead?

> +		if (!rpmhpd->enable_corner)
> +			rpmhpd->enable_corner = i;
> +
>  		/*
>  		 * The AUX data may be zero padded.  These 0 valued entries at
>  		 * the end of the map must be ignored.

-- 
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