From: Viresh Kumar <viresh.kumar@linaro.org>
To: Nicola Mazzucato <nicola.mazzucato@arm.com>
Cc: devicetree@vger.kernel.org, linux-pm@vger.kernel.org,
vireshk@kernel.org, daniel.lezcano@linaro.org, rjw@rjwysocki.net,
linux-kernel@vger.kernel.org, robh+dt@kernel.org,
linux-arm-kernel@lists.infradead.org,
Sudeep Holla <sudeep.holla@arm.com>,
chris.redpath@arm.com, Ionela Voinescu <ionela.voinescu@arm.com>,
morten.rasmussen@arm.com, Lukasz Luba <lukasz.luba@arm.com>
Subject: Re: [PATCH v2 2/2] [RFC] CPUFreq: Add support for cpu-perf-dependencies
Date: Tue, 20 Oct 2020 16:18:49 +0530 [thread overview]
Message-ID: <20201020104849.xh4prj4az5islmpt@vireshk-i7> (raw)
In-Reply-To: <e3b3a583-5e0f-f512-85e6-81c55a0e6db5@arm.com>
On 19-10-20, 14:36, Nicola Mazzucato wrote:
> Hi Viresh,
>
>
> On 10/19/20 10:46 AM, Viresh Kumar wrote:
> > On 19-10-20, 09:50, Nicola Mazzucato wrote:
> >> Hi Viresh,
> >>
> >> thank you for your suggestion on using 'opp-shared'.
> >> I think it could work for most of the cases we explained earlier.
> >>
> >> Summarising, there are two parts of this entire proposal:
> >> 1) where/how to get the information: now we are focusing on taking advantage of
> >> 'opp-shared' within an empty opp table
> >> 2) and how/where this information will be consumed
> >>
> >> Further details below:
> >>
> >> 1) a CPUFreq driver that takes the OPPs from firmware, can call
> >> dev_pm_opp_of_get_sharing_cpus like you suggested. When doing so, a provided
> >> cpumaksk will be populated with the corresponding cpus that share the same
> >> (empty) table opp in DT.
> >> All good so far.
> >
> > Great.
> >
> >> The current opp core is not expecting an empty table and therefore some errors
> >> are thrown when this happens.
> >> Since we are now allowing this corner-case, I am presenting below where I think
> >> some minor corrections may be needed:
> >>
> >> --- a/drivers/opp/of.c
> >> +++ b/drivers/opp/of.c
> >> @@ static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
> >> struct device_node *required_np, *np;
> >> int count, i;
> >>
> >> /* Traversing the first OPP node is all we need */
> >> np = of_get_next_available_child(opp_np, NULL);
> >> if (!np) {
> >> - dev_err(dev, "Empty OPP table\n");
> >> + dev_warn(dev, "Empty OPP table\n");
> >> +
> >> + /*
> >> + * With empty table we remove shared_opp. This is to leave the
> >> + * responsibility to decide which opp are shared to the opp users
> >> + */
> >> + opp_table->shared_opp = OPP_TABLE_ACCESS_EXCLUSIVE;
> >> +
> >> return;
> >> }
> >>
> >> @@ int dev_pm_opp_of_find_icc_paths(struct device *dev,
> >> int ret, i, count, num_paths;
> >> struct icc_path **paths;
> >>
> >> ret = _bandwidth_supported(dev, opp_table);
> >> - if (ret <= 0)
> >> + if (ret == -EINVAL)
> >> + return 0; /* Empty OPP table is a valid corner-case, let's not
> >> fail */
> >> + else if (ret <= 0)
> >> return ret;
> >>
> >> The above are not 'strictly' necessary to achieve the intended goal, but they
> >> make clearer that an empty table is now allowed and not an error anymore.
> >> What it is your point of view on this?
> >
> > Why is this stuff getting called in your case ? We shouldn't be trying
> > to create an OPP table here and it should still be an error in the
> > code if we are asked to parse an empty OPP table.
>
> A driver that gets a set of opp-points from f/w needs to add them to each
> device. To do so, it will call dev_pm_opp_add(). If an opp_table struct for this
> device is not found, one will be created and the opp-point will be added to it.
> When allocation a new opp_table the opp will try to initialise it by parsing the
> values in DT. It will also try to find_icc_paths.
>
> Everything happens silently if we don't have a table in DT.
Right, you need something like your patch here.
--
viresh
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next prev parent reply other threads:[~2020-10-20 10:50 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-24 9:53 [PATCH v2 0/2] CPUFreq: Add support for cpu performance dependencies Nicola Mazzucato
2020-09-24 9:53 ` [PATCH v2 1/2] dt-bindings: arm: Add devicetree binding for cpu-performance-dependencies Nicola Mazzucato
2020-10-08 13:42 ` Ionela Voinescu
2020-09-24 9:53 ` [PATCH v2 2/2] [RFC] CPUFreq: Add support for cpu-perf-dependencies Nicola Mazzucato
2020-10-06 7:19 ` Viresh Kumar
2020-10-07 12:58 ` Nicola Mazzucato
2020-10-08 11:02 ` Viresh Kumar
2020-10-08 15:03 ` Ionela Voinescu
2020-10-08 15:57 ` Rafael J. Wysocki
2020-10-08 17:08 ` Ionela Voinescu
2020-10-12 16:06 ` Sudeep Holla
2020-10-08 16:00 ` Nicola Mazzucato
2020-10-09 5:39 ` Viresh Kumar
2020-10-09 11:10 ` Nicola Mazzucato
2020-10-09 11:17 ` Viresh Kumar
2020-10-09 14:01 ` Rob Herring
2020-10-09 15:28 ` Nicola Mazzucato
2020-10-12 4:19 ` Viresh Kumar
2020-10-12 10:22 ` Lukasz Luba
2020-10-12 10:50 ` Rafael J. Wysocki
2020-10-12 11:05 ` Lukasz Luba
2020-10-12 10:59 ` Ionela Voinescu
2020-10-12 13:48 ` Lukasz Luba
2020-10-12 16:30 ` Ionela Voinescu
2020-10-12 18:19 ` Lukasz Luba
2020-10-12 22:01 ` Ionela Voinescu
2020-10-13 11:53 ` Rafael J. Wysocki
2020-10-13 12:39 ` Ionela Voinescu
2020-10-15 15:56 ` Rafael J. Wysocki
2020-10-15 18:38 ` Ionela Voinescu
2020-10-12 13:59 ` Rob Herring
2020-10-12 16:02 ` Sudeep Holla
2020-10-12 15:54 ` Sudeep Holla
2020-10-12 15:49 ` Sudeep Holla
2020-10-12 16:52 ` Ionela Voinescu
2020-10-12 17:18 ` Lukasz Luba
2020-10-14 4:25 ` Viresh Kumar
2020-10-14 9:11 ` Lukasz Luba
2020-10-19 8:50 ` Nicola Mazzucato
2020-10-19 9:46 ` Viresh Kumar
2020-10-19 13:36 ` Nicola Mazzucato
2020-10-20 10:48 ` Viresh Kumar [this message]
2020-10-13 13:53 ` Lukasz Luba
2020-10-14 4:20 ` Viresh Kumar
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