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Date:   Tue, 24 Oct 2023 13:18:50 +0200
From:   Stephan Gerhold <stephan.gerhold@kernkonzept.com>
To:     Viresh Kumar <viresh.kumar@linaro.org>
Cc:     Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
        Stephen Boyd <sboyd@kernel.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>, linux-pm@vger.kernel.org,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] OPP: Call dev_pm_opp_set_opp() for required OPPs
Message-ID: <ZTeoGiMQZ-OoYJBG@kernkonzept.com>
References: <cover.1697710527.git.viresh.kumar@linaro.org>
 <6de4fcb5bb943a131d0cdf0a858bd35af02a2f88.1697710527.git.viresh.kumar@linaro.org>
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On Thu, Oct 19, 2023 at 03:52:01PM +0530, Viresh Kumar wrote:
> Configuring the required OPP was never properly implemented, we just
> took an exception for genpds and configured them directly, while leaving
> out all other required OPP types.
> 
> Now that a standard call to dev_pm_opp_set_opp() takes care of
> configuring the opp->level too, the special handling for genpds can be
> avoided by simply calling dev_pm_opp_set_opp() for the required OPPs,
> which shall eventually configure the corresponding level for genpds.
> 
> This also makes it possible for us to configure other type of required
> OPPs (no concrete users yet though), via the same path. This is how
> other frameworks take care of parent nodes, like clock, regulators, etc,
> where we recursively call the same helper.
> 
> In order to call dev_pm_opp_set_opp() for the virtual genpd devices,
> they must share the OPP table of the genpd. Call _add_opp_dev() for them
> to get that done.
> 
> This commit also extends the struct dev_pm_opp_config to pass required
> devices, for non-genpd cases, which can be used to call
> dev_pm_opp_set_opp() for the non-genpd required devices.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>  drivers/opp/core.c     | 144 ++++++++++++++++++-----------------------
>  drivers/opp/of.c       |  12 ++--
>  drivers/opp/opp.h      |   8 +--
>  include/linux/pm_opp.h |   7 +-
>  4 files changed, 76 insertions(+), 95 deletions(-)
> 
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index aab8c8e79146..056b51abc501 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -1046,42 +1046,19 @@ static int _set_opp_bw(const struct opp_table *opp_table,
>  	return 0;
>  }
>  
> -static int _set_performance_state(struct device *dev, struct device *pd_dev,
> -				  struct dev_pm_opp *opp, int i)
> -{
> -	unsigned int pstate = likely(opp) ? opp->required_opps[i]->level: 0;

Unfortunately this patch breaks scaling the performance state of the
virtual genpd devices completely. As far as I can tell it just keeps
setting level = 0 for every OPP switch (this is on MSM8909 with [1],
a single "perf" power domain attached to the CPU):

[  457.252255] cpu cpu0: _set_opp: switching OPP: Freq 998400000 -> 799999804 Hz, Level 0 -> 0, Bw 3200000 -> 1600000
[  457.253739] genpd genpd:1:cpu0: _set_opp: switching OPP: Freq 998400000 -> 799999804 Hz, Level 0 -> 0, Bw 3200000 -> 1600000
[  457.304581] cpu cpu0: _set_opp: switching OPP: Freq 799999804 -> 533333202 Hz, Level 0 -> 0, Bw 1600000 -> 1600000
[  457.306091] genpd genpd:1:cpu0: _set_opp: switching OPP: Freq 799999804 -> 533333202 Hz, Level 0 -> 0, Bw 1600000 -> 1600000
[  457.323489] cpu cpu0: _set_opp: switching OPP: Freq 533333202 -> 399999902 Hz, Level 0 -> 0, Bw 1600000 -> 800000
[  457.352792] genpd genpd:1:cpu0: _set_opp: switching OPP: Freq 533333202 -> 399999902 Hz, Level 0 -> 0, Bw 1600000 -> 800000
[  457.353056] cpu cpu0: _set_opp: switching OPP: Freq 399999902 -> 199999951 Hz, Level 0 -> 0, Bw 800000 -> 800000
[  457.355285] genpd genpd:1:cpu0: _set_opp: switching OPP: Freq 399999902 -> 199999951 Hz, Level 0 -> 0, Bw 800000 -> 800000

Where do you handle setting the pstate specified in the "required-opps"
of the OPP table with this patch? I've looked at your changes for some
time but must admit I haven't really understood how it is supposed to
work. :-)

Thanks,
Stephan

[1]: https://lore.kernel.org/linux-arm-msm/20231018-msm8909-cpufreq-v2-0-0962df95f654@kernkonzept.com/

> -	int ret;
> -
> -	if (!pd_dev)
> -		return 0;
> -
> -	ret = dev_pm_domain_set_performance_state(pd_dev, pstate);
> -	if (ret) {
> -		dev_err(dev, "Failed to set performance state of %s: %d (%d)\n",
> -			dev_name(pd_dev), pstate, ret);
> -	}
> -
> -	return ret;
> -}
> -
> -static int _opp_set_required_opps_generic(struct device *dev,
> -	struct opp_table *opp_table, struct dev_pm_opp *opp, bool scaling_down)
> -{
> -	dev_err(dev, "setting required-opps isn't supported for non-genpd devices\n");
> -	return -ENOENT;
> -}
> -
> -static int _opp_set_required_opps_genpd(struct device *dev,
> -	struct opp_table *opp_table, struct dev_pm_opp *opp, bool scaling_down)
> +/* This is only called for PM domain for now */
> +static int _set_required_opps(struct device *dev, struct opp_table *opp_table,
> +			      struct dev_pm_opp *opp, bool up)
>  {
> -	struct device **genpd_virt_devs = opp_table->genpd_virt_devs;
> +	struct device **devs = opp_table->required_devs;
>  	int index, target, delta, ret;
>  
> -	if (!genpd_virt_devs)
> -		return 0;
> +	/* required-opps not fully initialized yet */
> +	if (lazy_linking_pending(opp_table))
> +		return -EBUSY;
>  
>  	/* Scaling up? Set required OPPs in normal order, else reverse */
> -	if (!scaling_down) {
> +	if (up) {
>  		index = 0;
>  		target = opp_table->required_opp_count;
>  		delta = 1;
> @@ -1092,9 +1069,11 @@ static int _opp_set_required_opps_genpd(struct device *dev,
>  	}
>  
>  	while (index != target) {
> -		ret = _set_performance_state(dev, genpd_virt_devs[index], opp, index);
> -		if (ret)
> -			return ret;
> +		if (devs[index]) {
> +			ret = dev_pm_opp_set_opp(devs[index], opp);
> +			if (ret)
> +				return ret;
> +		}
>  
>  		index += delta;
>  	}
> @@ -1102,34 +1081,6 @@ static int _opp_set_required_opps_genpd(struct device *dev,
>  	return 0;
>  }
>  
> -/* This is only called for PM domain for now */
> -static int _set_required_opps(struct device *dev, struct opp_table *opp_table,
> -			      struct dev_pm_opp *opp, bool up)
> -{
> -	/* required-opps not fully initialized yet */
> -	if (lazy_linking_pending(opp_table))
> -		return -EBUSY;
> -
> -	if (opp_table->set_required_opps)
> -		return opp_table->set_required_opps(dev, opp_table, opp, up);
> -
> -	return 0;
> -}
> -
> -/* Update set_required_opps handler */
> -void _update_set_required_opps(struct opp_table *opp_table)
> -{
> -	/* Already set */
> -	if (opp_table->set_required_opps)
> -		return;
> -
> -	/* All required OPPs will belong to genpd or none */
> -	if (opp_table->required_opp_tables[0]->is_genpd)
> -		opp_table->set_required_opps = _opp_set_required_opps_genpd;
> -	else
> -		opp_table->set_required_opps = _opp_set_required_opps_generic;
> -}
> -
>  static int _set_opp_level(struct device *dev, struct opp_table *opp_table,
>  			  struct dev_pm_opp *opp)
>  {
> @@ -2390,19 +2341,13 @@ static void _opp_detach_genpd(struct opp_table *opp_table)
>  {
>  	int index;
>  
> -	if (!opp_table->genpd_virt_devs)
> -		return;
> -
>  	for (index = 0; index < opp_table->required_opp_count; index++) {
> -		if (!opp_table->genpd_virt_devs[index])
> +		if (!opp_table->required_devs[index])
>  			continue;
>  
> -		dev_pm_domain_detach(opp_table->genpd_virt_devs[index], false);
> -		opp_table->genpd_virt_devs[index] = NULL;
> +		dev_pm_domain_detach(opp_table->required_devs[index], false);
> +		opp_table->required_devs[index] = NULL;
>  	}
> -
> -	kfree(opp_table->genpd_virt_devs);
> -	opp_table->genpd_virt_devs = NULL;
>  }
>  
>  /*
> @@ -2429,15 +2374,10 @@ static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev,
>  	int index = 0, ret = -EINVAL;
>  	const char * const *name = names;
>  
> -	if (opp_table->genpd_virt_devs)
> +	/* Checking only the first one is enough ? */
> +	if (opp_table->required_devs[0])
>  		return 0;
>  
> -	opp_table->genpd_virt_devs = kcalloc(opp_table->required_opp_count,
> -					     sizeof(*opp_table->genpd_virt_devs),
> -					     GFP_KERNEL);
> -	if (!opp_table->genpd_virt_devs)
> -		return -ENOMEM;
> -
>  	while (*name) {
>  		if (index >= opp_table->required_opp_count) {
>  			dev_err(dev, "Index can't be greater than required-opp-count - 1, %s (%d : %d)\n",
> @@ -2452,13 +2392,25 @@ static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev,
>  			goto err;
>  		}
>  
> -		opp_table->genpd_virt_devs[index] = virt_dev;
> +		/*
> +		 * Add the virtual genpd device as a user of the OPP table, so
> +		 * we can call dev_pm_opp_set_opp() on it directly.
> +		 *
> +		 * This will be automatically removed when the OPP table is
> +		 * removed, don't need to handle that here.
> +		 */
> +		if (!_add_opp_dev(virt_dev, opp_table->required_opp_tables[index])) {
> +			ret = -ENOMEM;
> +			goto err;
> +		}
> +
> +		opp_table->required_devs[index] = virt_dev;
>  		index++;
>  		name++;
>  	}
>  
>  	if (virt_devs)
> -		*virt_devs = opp_table->genpd_virt_devs;
> +		*virt_devs = opp_table->required_devs;
>  
>  	return 0;
>  
> @@ -2468,10 +2420,34 @@ static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev,
>  
>  }
>  
> +static void _opp_set_required_devs(struct opp_table *opp_table,
> +				   struct device **required_devs)
> +{
> +	int i;
> +
> +	/* Another CPU that shares the OPP table has set the required devs ? */
> +	if (opp_table->required_devs[0])
> +		return;
> +
> +	for (i = 0; i < opp_table->required_opp_count; i++)
> +		opp_table->required_devs[i] = required_devs[i];
> +}
> +
> +static void _opp_put_required_devs(struct opp_table *opp_table)
> +{
> +	int i;
> +
> +	for (i = 0; i < opp_table->required_opp_count; i++)
> +		opp_table->required_devs[i] = NULL;
> +}
> +
>  static void _opp_clear_config(struct opp_config_data *data)
>  {
> -	if (data->flags & OPP_CONFIG_GENPD)
> +	if (data->flags & OPP_CONFIG_REQUIRED_DEVS)
> +		_opp_put_required_devs(data->opp_table);
> +	else if (data->flags & OPP_CONFIG_GENPD)
>  		_opp_detach_genpd(data->opp_table);
> +
>  	if (data->flags & OPP_CONFIG_REGULATOR)
>  		_opp_put_regulators(data->opp_table);
>  	if (data->flags & OPP_CONFIG_SUPPORTED_HW)
> @@ -2585,12 +2561,18 @@ int dev_pm_opp_set_config(struct device *dev, struct dev_pm_opp_config *config)
>  
>  	/* Attach genpds */
>  	if (config->genpd_names) {
> +		if (config->required_devs)
> +			goto err;
> +
>  		ret = _opp_attach_genpd(opp_table, dev, config->genpd_names,
>  					config->virt_devs);
>  		if (ret)
>  			goto err;
>  
>  		data->flags |= OPP_CONFIG_GENPD;
> +	} else if (config->required_devs) {
> +		_opp_set_required_devs(opp_table, config->required_devs);
> +		data->flags |= OPP_CONFIG_REQUIRED_DEVS;
>  	}
>  
>  	ret = xa_alloc(&opp_configs, &id, data, XA_LIMIT(1, INT_MAX),
> diff --git a/drivers/opp/of.c b/drivers/opp/of.c
> index e056f31a48b5..27659d23d54d 100644
> --- a/drivers/opp/of.c
> +++ b/drivers/opp/of.c
> @@ -165,7 +165,7 @@ static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
>  	struct opp_table **required_opp_tables;
>  	struct device_node *required_np, *np;
>  	bool lazy = false;
> -	int count, i;
> +	int count, i, size;
>  
>  	/* Traversing the first OPP node is all we need */
>  	np = of_get_next_available_child(opp_np, NULL);
> @@ -179,12 +179,13 @@ static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
>  	if (count <= 0)
>  		goto put_np;
>  
> -	required_opp_tables = kcalloc(count, sizeof(*required_opp_tables),
> -				      GFP_KERNEL);
> +	size = sizeof(*required_opp_tables) + sizeof(*opp_table->required_devs);
> +	required_opp_tables = kcalloc(count, size, GFP_KERNEL);
>  	if (!required_opp_tables)
>  		goto put_np;
>  
>  	opp_table->required_opp_tables = required_opp_tables;
> +	opp_table->required_devs = (void *)(required_opp_tables + count);
>  	opp_table->required_opp_count = count;
>  
>  	for (i = 0; i < count; i++) {
> @@ -208,8 +209,6 @@ static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
>  		mutex_lock(&opp_table_lock);
>  		list_add(&opp_table->lazy, &lazy_opp_tables);
>  		mutex_unlock(&opp_table_lock);
> -	} else {
> -		_update_set_required_opps(opp_table);
>  	}
>  
>  	goto put_np;
> @@ -328,7 +327,7 @@ static int _link_required_opps(struct dev_pm_opp *opp, struct opp_table *opp_tab
>  	 * dev_pm_opp_set_opp() will take care of in the normal path itself.
>  	 */
>  	if (required_table->is_genpd && opp_table->required_opp_count == 1 &&
> -	    !opp_table->genpd_virt_devs) {
> +	    !opp_table->required_devs[0]) {
>  		if (!WARN_ON(opp->level))
>  			opp->level = opp->required_opps[0]->level;
>  	}
> @@ -441,7 +440,6 @@ static void lazy_link_required_opp_table(struct opp_table *new_table)
>  
>  		/* All required opp-tables found, remove from lazy list */
>  		if (!lazy) {
> -			_update_set_required_opps(opp_table);
>  			list_del_init(&opp_table->lazy);
>  
>  			list_for_each_entry(opp, &opp_table->opp_list, node)
> diff --git a/drivers/opp/opp.h b/drivers/opp/opp.h
> index 08366f90f16b..23dcb2fbf8c3 100644
> --- a/drivers/opp/opp.h
> +++ b/drivers/opp/opp.h
> @@ -35,6 +35,7 @@ extern struct list_head opp_tables;
>  #define OPP_CONFIG_PROP_NAME		BIT(3)
>  #define OPP_CONFIG_SUPPORTED_HW		BIT(4)
>  #define OPP_CONFIG_GENPD		BIT(5)
> +#define OPP_CONFIG_REQUIRED_DEVS	BIT(6)
>  
>  /**
>   * struct opp_config_data - data for set config operations
> @@ -160,9 +161,9 @@ enum opp_table_access {
>   * @rate_clk_single: Currently configured frequency for single clk.
>   * @current_opp: Currently configured OPP for the table.
>   * @suspend_opp: Pointer to OPP to be used during device suspend.
> - * @genpd_virt_devs: List of virtual devices for multiple genpd support.
>   * @required_opp_tables: List of device OPP tables that are required by OPPs in
>   *		this table.
> + * @required_devs: List of devices for required OPP tables.
>   * @required_opp_count: Number of required devices.
>   * @supported_hw: Array of version number to support.
>   * @supported_hw_count: Number of elements in supported_hw array.
> @@ -180,7 +181,6 @@ enum opp_table_access {
>   * @path_count: Number of interconnect paths
>   * @enabled: Set to true if the device's resources are enabled/configured.
>   * @is_genpd: Marks if the OPP table belongs to a genpd.
> - * @set_required_opps: Helper responsible to set required OPPs.
>   * @dentry:	debugfs dentry pointer of the real device directory (not links).
>   * @dentry_name: Name of the real dentry.
>   *
> @@ -211,8 +211,8 @@ struct opp_table {
>  	struct dev_pm_opp *current_opp;
>  	struct dev_pm_opp *suspend_opp;
>  
> -	struct device **genpd_virt_devs;
>  	struct opp_table **required_opp_tables;
> +	struct device **required_devs;
>  	unsigned int required_opp_count;
>  
>  	unsigned int *supported_hw;
> @@ -229,8 +229,6 @@ struct opp_table {
>  	unsigned int path_count;
>  	bool enabled;
>  	bool is_genpd;
> -	int (*set_required_opps)(struct device *dev,
> -		struct opp_table *opp_table, struct dev_pm_opp *opp, bool scaling_down);
>  
>  #ifdef CONFIG_DEBUG_FS
>  	struct dentry *dentry;
> diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
> index ccd97bcef269..25f7bcbea7ab 100644
> --- a/include/linux/pm_opp.h
> +++ b/include/linux/pm_opp.h
> @@ -74,8 +74,10 @@ typedef int (*config_clks_t)(struct device *dev, struct opp_table *opp_table,
>   * @supported_hw_count: Number of elements in the array.
>   * @regulator_names: Array of pointers to the names of the regulator, NULL terminated.
>   * @genpd_names: Null terminated array of pointers containing names of genpd to
> - *		 attach.
> - * @virt_devs: Pointer to return the array of virtual devices.
> + *		attach. Mutually exclusive with required_devs.
> + * @virt_devs: Pointer to return the array of genpd virtual devices. Mutually
> + *		exclusive with required_devs.
> + * @required_devs: Required OPP devices. Mutually exclusive with genpd_names/virt_devs.
>   *
>   * This structure contains platform specific OPP configurations for the device.
>   */
> @@ -90,6 +92,7 @@ struct dev_pm_opp_config {
>  	const char * const *regulator_names;
>  	const char * const *genpd_names;
>  	struct device ***virt_devs;
> +	struct device **required_devs;
>  };
>  
>  /**
> -- 
> 2.31.1.272.g89b43f80a514
> 

-- 
Stephan Gerhold <stephan.gerhold@kernkonzept.com>
Kernkonzept GmbH at Dresden, Germany, HRB 31129, CEO Dr.-Ing. Michael Hohmuth