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Date: Wed, 1 May 2013 09:41:20 -0500
From: Nishanth Menon <nm@...com>
To: <Sudeep.KarkadaNagesha@....com>
CC: <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
Grant Likely <grant.likely@...aro.org>,
Rob Herring <rob.herring@...xeda.com>,
Rob Landley <rob@...dley.net>,
"Rafael J. Wysocki" <rjw@...k.pl>,
Shawn Guo <shawn.guo@...aro.org>,
<devicetree-discuss@...ts.ozlabs.org>, <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 1/2] PM / OPP: add support to specify phandle of another
node for OPP
On 12:11-20130501, Sudeep.KarkadaNagesha@....com wrote:
> From: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
>
> If more than one similar devices share the same OPPs, currently we
> need to replicate the OPP entries in all the nodes.
Nice, thanks.
>
> Few drivers like cpufreq depend on physical cpu0 node to specify the
cpufreq-cpu0?
> OPPs and only that node is referred irrespective of the logical cpu
> accessing it. Alternatively to support cpuhotplug path, few drivers
> parse all the cpu nodes for OPPs. Instead we can specify the phandle
> of the node with which the current node shares the operating points.
>
> This patch adds support to specify the phandle in the operating points
> of any device node, where the node specified by the phandle holds the
> actual OPPs.
>
> Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
> ---
> Documentation/devicetree/bindings/power/opp.txt | 41 +++++++++++++++++++++++
> drivers/base/power/opp.c | 30 ++++++++++++-----
> 2 files changed, 63 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/power/opp.txt b/Documentation/devicetree/bindings/power/opp.txt
> index 74499e5..a659da4 100644
> --- a/Documentation/devicetree/bindings/power/opp.txt
> +++ b/Documentation/devicetree/bindings/power/opp.txt
> @@ -23,3 +23,44 @@ cpu@0 {
> 198000 850000
> >;
> };
> +
Definition of operating-points is now a little different in the
original description - it still indicates tuple {freq,voltage}, where
as, this patch allows phandle to a different device's operating-points
to be used. - we might want to rephrase the description.
btw, to device-tree folks, I am not sure if it is OK to have different formats
for the same property like operating-points. At least I don't seem to
quickly be able to find any precedence.
> +If more than one device of same type share the same OPPs, e.g. all the CPUs on
s/e.g/example?
> +a SoC or in a single cluster on a SoC, then we need to avoid replicating the
> +OPPs in all the nodes. We can specify the phandle of the node with which the
> +current node shares the operating points instead.
> +
> +Examples:
> +Consider an SMP with 4 CPUs all sharing the same OPPs.
We might want to descr
> +
> +cpu0: cpu@0 {
> + compatible = "arm,cortex-a9";
> + reg = <0>;
> + next-level-cache = <&L2>;
> + operating-points = <
> + /* kHz uV */
> + 792000 1100000
> + 396000 950000
> + 198000 850000
> + >;
> +};
> +
> +cpu1: cpu@1 {
> + compatible = "arm,cortex-a9";
> + reg = <1>;
> + next-level-cache = <&L2>;
> + operating-points = <&cpu0>;
> +};
> +
> +cpu2: cpu@2 {
> + compatible = "arm,cortex-a9";
> + reg = <2>;
> + next-level-cache = <&L2>;
> + operating-points = <&cpu0>;
> +};
> +
> +cpu3: cpu@3 {
> + compatible = "arm,cortex-a9";
> + reg = <3>;
> + next-level-cache = <&L2>;
> + operating-points = <&cpu0>;
> +};
> diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
> index f0077cb..4dfdc01 100644
> --- a/drivers/base/power/opp.c
> +++ b/drivers/base/power/opp.c
> @@ -698,19 +698,15 @@ struct srcu_notifier_head *opp_get_notifier(struct device *dev)
> }
>
> #ifdef CONFIG_OF
> -/**
> - * of_init_opp_table() - Initialize opp table from device tree
> - * @dev: device pointer used to lookup device OPPs.
> - *
> - * Register the initial OPP table with the OPP library for given device.
> - */
> -int of_init_opp_table(struct device *dev)
> +static int of_init_opp_table_from_ofnode(struct device *dev,
> + struct device_node *of_node)
please provide kernel-doc documentation for static function as well -
this is inline with the rest of the file.
> {
> + struct device_opp *dev_opp = NULL;
dev_opp is not used until patch #2 - please introduce it in that patch.
> const struct property *prop;
> const __be32 *val;
> int nr;
>
> - prop = of_find_property(dev->of_node, "operating-points", NULL);
> + prop = of_find_property(of_node, "operating-points", NULL);
> if (!prop)
> return -ENODEV;
> if (!prop->value)
> @@ -722,6 +718,14 @@ int of_init_opp_table(struct device *dev)
> */
> nr = prop->length / sizeof(u32);
> if (nr % 2) {
> + if (nr == 1) {
> + struct device_node *opp_node;
> + opp_node = of_parse_phandle(dev->of_node,
> + "operating-points", 0);
> + if (opp_node)
> + return of_init_opp_table_from_ofnode(dev,
> + opp_node);
> + }
if operating-points=<100000>, then we return Invalid OPP list
if operating-points=<&uart3>; (some phandle that does not have
operating-points), there is no helpful warning in log except -ENODEV is
returned - we might want to add some info here?
> dev_err(dev, "%s: Invalid OPP list\n", __func__);
> return -EINVAL;
> }
> @@ -741,5 +745,15 @@ int of_init_opp_table(struct device *dev)
>
> return 0;
> }
missing EOL?
> +/**
> + * of_init_opp_table() - Initialize opp table from device tree
> + * @dev: device pointer used to lookup device OPPs.
> + *
> + * Register the initial OPP table with the OPP library for given device.
> + */
> +int of_init_opp_table(struct device *dev)
> +{
> + return of_init_opp_table_from_ofnode(dev, dev->of_node);
> +}
> EXPORT_SYMBOL_GPL(of_init_opp_table);
> #endif
> --
> 1.7.10.4
>
>
> --
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--
Regards,
Nishanth Menon
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