From: Gregory CLEMENT <gregory.clement@bootlin.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: "Andrew Lunn" <andrew@lunn.ch>,
"Jason Cooper" <jason@lakedaemon.net>,
linux-pm@vger.kernel.org,
"Antoine Tenart" <antoine.tenart@bootlin.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
"Maxime Chevallier" <maxime.chevallier@bootlin.com>,
"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
"Miquèl Raynal" <miquel.raynal@bootlin.com>,
linux-arm-kernel@lists.infradead.org,
"Sebastian Hesselbarth" <sebastian.hesselbarth@gmail.com>
Subject: Re: [PATCH v3 2/2] cpufreq: ap806: add cpufreq driver for Armada 8K
Date: Tue, 18 Dec 2018 15:32:28 +0100 [thread overview]
Message-ID: <87mup2hpmr.fsf@bootlin.com> (raw)
In-Reply-To: <20181217111026.7b3tds2yz4g7opdt@vireshk-i7> (Viresh Kumar's message of "Mon, 17 Dec 2018 16:40:26 +0530")
Hi Viresh,
On lun., déc. 17 2018, Viresh Kumar <viresh.kumar@linaro.org> wrote:
> On 11-12-18, 17:42, Gregory CLEMENT wrote:
>> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
>> index 4e1131ef85ae..7e32a241760d 100644
>> --- a/drivers/cpufreq/Kconfig.arm
>> +++ b/drivers/cpufreq/Kconfig.arm
>> @@ -25,6 +25,17 @@ config ARM_ARMADA_37XX_CPUFREQ
>> This adds the CPUFreq driver support for Marvell Armada 37xx SoCs.
>> The Armada 37xx PMU supports 4 frequency and VDD levels.
>>
>> +config ARM_ARMADA_8K_CPUFREQ
>> + tristate "Armada 8K CPUFreq driver"
>> + depends on ARCH_MVEBU && CPUFREQ_DT
>> + help
>> + This enables the CPUFreq driver support for Marvell
>> + Armada8k SOCs.
>> + Armada8K device has the AP806 which supports scaling
>> + to any full integer divider.
>> +
>> + If in doubt, say N.
>> +
>> # big LITTLE core layer and glue drivers
>> config ARM_BIG_LITTLE_CPUFREQ
>> tristate "Generic ARM big LITTLE CPUfreq driver"
>> diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
>> index d5ee4562ed06..db1564b610ac 100644
>> --- a/drivers/cpufreq/Makefile
>> +++ b/drivers/cpufreq/Makefile
>> @@ -50,6 +50,7 @@ obj-$(CONFIG_X86_SFI_CPUFREQ) += sfi-cpufreq.o
>> obj-$(CONFIG_ARM_BIG_LITTLE_CPUFREQ) += arm_big_little.o
>>
>> obj-$(CONFIG_ARM_ARMADA_37XX_CPUFREQ) += armada-37xx-cpufreq.o
>> +obj-$(CONFIG_ARM_ARMADA_8K_CPUFREQ) += armada-8k-cpufreq.o
>> obj-$(CONFIG_ARM_BRCMSTB_AVS_CPUFREQ) += brcmstb-avs-cpufreq.o
>> obj-$(CONFIG_ACPI_CPPC_CPUFREQ) += cppc_cpufreq.o
>> obj-$(CONFIG_ARCH_DAVINCI) += davinci-cpufreq.o
>> diff --git a/drivers/cpufreq/armada-8k-cpufreq.c b/drivers/cpufreq/armada-8k-cpufreq.c
>> new file mode 100644
>> index 000000000000..1db1953fb43e
>> --- /dev/null
>> +++ b/drivers/cpufreq/armada-8k-cpufreq.c
>> @@ -0,0 +1,186 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/*
>> + * CPUFreq support for Armada 8K
>> + *
>> + * Copyright (C) 2018 Marvell
>> + *
>> + * Omri Itach <omrii@marvell.com>
>> + * Gregory Clement <gregory.clement@bootlin.com>
>> + */
>> +
>> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>> +
>> +#include <linux/clk.h>
>> +#include <linux/cpu.h>
>> +#include <linux/err.h>
>> +#include <linux/init.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/pm_opp.h>
>> +#include <linux/slab.h>
>> +
>> +/*
>> + * Setup the opps list with the divider for the max frequency, that
>> + * will be filled at runtime.
>> + */
>> +static const int opps_div[] __initconst = {1, 2, 3, 4};
>> +
>> +static struct platform_device *armada_8k_pdev;
>> +static struct freq_table *freq_tables;
>> +static int opps_index;
>> +
>> +struct freq_table {
>> + struct device *cpu_dev;
>> + struct clk *clk;
>> + unsigned int freq[ARRAY_SIZE(opps_div)];
>> +};
>> +
>> +/* If the CPUs share the same clock, then they are in the same cluster. */
>> +static void __init armada_8k_get_sharing_cpus(struct clk *cur_clk,
>> + struct cpumask *cpumask)
>> +{
>> + int cpu;
>> +
>> + for_each_possible_cpu(cpu) {
>> + struct device *cpu_dev = get_cpu_device(cpu);
>
> What if this fails ?
cpu_dev will be NULL so the clk_get() will fail to find the clock which
is handled just after.
But if needed we can add this extra test and differed the clk_get.
>
>> + struct clk *clk = clk_get(cpu_dev, 0);
>> +
>> + if (IS_ERR(clk))
>> + dev_warn(cpu_dev, "Cannot get clock for CPU %d\n", cpu);
>> + else if (clk_is_match(clk, cur_clk))
>> + cpumask_set_cpu(cpu, cpumask);
>> +
>> + clk_put(clk);
>
> So you will do clk_put() even if clk_get() failed, that will trigger a WARN() if
> I am not wrong.
Yes there is a WARN_ONCE in this case, I can move the clk_put in the
else part.
>
>> + }
>> +}
>> +
>> +static int armada_8k_add_opp(struct clk *clk, struct device *cpu_dev,
>> + struct freq_table *freq_tables, int opps_index)
>> +{
>> + unsigned int cur_frequency;
>> + unsigned int freq;
>> + int i, ret;
>> +
>> + /* Get nominal (current) CPU frequency. */
>> + cur_frequency = clk_get_rate(clk);
>> +
>> + if (!cur_frequency) {
>> + dev_err(cpu_dev,
>> + "Failed to get clock rate for this CPU\n");
>> + return -EINVAL;
>> + }
>> +
>> + freq_tables[opps_index].cpu_dev = cpu_dev;
>> + for (i = 0; i < ARRAY_SIZE(opps_div); i++) {
>> + freq = cur_frequency / opps_div[i];
>> +
>> + ret = dev_pm_opp_add(cpu_dev, freq, 0);
>> + if (ret)
>> + return ret;
>> +
>> + freq_tables[opps_index].freq[i] = freq;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static void armada_8k_cpufreq_free_table(void)
>> +{
>> + opps_index--;
>> + for (; opps_index >= 0; opps_index--) {
>> + int i;
>> +
>> + for (i = 0; i < ARRAY_SIZE(opps_div); i++)
>> + dev_pm_opp_remove(freq_tables[opps_index].cpu_dev,
>> + freq_tables[opps_index].freq[i]);
>> + }
>> +
>> + kfree(freq_tables);
>> +}
>> +
>> +static int __init armada_8k_cpufreq_init(void)
>> +{
>> + int ret = 0, cpu, nb_cpus;
>> + struct device_node *node;
>> +
>> + node = of_find_compatible_node(NULL, NULL, "marvell,ap806-cpu-clock");
>> + if (!node || !of_device_is_available(node))
>> + return -ENODEV;
>> +
>> + nb_cpus = num_possible_cpus();
>> + freq_tables = kcalloc(nb_cpus, sizeof(*freq_tables), GFP_KERNEL);
>
> Add a blank line here.
OK
>
>> + /*
>> + * For each CPU, this loop registers the operating points
>> + * supported (which are the nominal CPU frequency and full integer
>> + * divisions of it).
>> + */
>> + for_each_possible_cpu(cpu) {
>> + struct device *cpu_dev;
>> + struct cpumask cpus;
>> + struct clk *clk;
>> + int i, skip;
>> +
>> + skip = 0;
>> + cpu_dev = get_cpu_device(cpu);
>> +
>> + if (!cpu_dev) {
>> + dev_err(cpu_dev, "Cannot get CPU %d\n", cpu);
>> + continue;
>> + }
>> +
>> + clk = devm_clk_get(cpu_dev, 0);
>
> I don't think you should call devm_*() helpers on the cpu_dev pointer, this is
> not like the platform device structure. The problem is that no driver gets
> attached/detached from cpu_dev and so the resources may never get
> free.
OK
>
>> +
>> + if (IS_ERR(clk)) {
>> + dev_err(cpu_dev, "Cannot get clock for CPU %d\n", cpu);
>> + ret = PTR_ERR(clk);
>> + goto remove_opp;
>> + }
>> +
>> + for (i = 0; i < nb_cpus; i++) {
>> + if (clk_is_match(clk, freq_tables[i].clk)) {
>> + skip = 1;
>
> Why not do devm_clk_put() from right here and "continue" after that. That way
> you can avoid "skip" variable as well.
We need to keep a reference to the clk when it used later in the loop.
> Also why are you doing this clk-match at all ? This looks similar to what
> armada_8k_get_sharing_cpus() is doing. You can optimize this stuff better I
> believe.
>
> I will do this:
>
> Create a cpumask variable and assign possible_cpus mask to it. And then after
> each iteration of this loop, I clear "cpus" (returned from
> armada_8k_get_sharing_cpus()) from the CPUs from that cpumask. That way the loop
> will never try the second CPU from the same cpumask again.
I will try it
>
>> + break;
>> + }
>> + }
>> + if (skip) {
>> + devm_clk_put(cpu_dev, clk);
>> + continue;
>> + }
>> +
>> + freq_tables[opps_index].clk = clk;
>> +
>> + ret = armada_8k_add_opp(clk, cpu_dev, freq_tables, opps_index);
>
> And this opps_index thing is not very clean. Having a global variable this way
> makes things very messy, which is being updated from several routines.
I think you missed the fact that no variable are passed to the exit
function but we still need to have a reference on the OPP to free, so we
cant do without this global variable. However I could reduce the amount
by hiding them in a platform data associated to the platform_device.
>
> So if armada_8k_add_opp() fails after adding few OPPs, we will now call
> armada_8k_cpufreq_free_table() which will first do opps_index-- and so you may
> miss freeing the OPPs added during the last call to armada_8k_add_opp().
>
Actually opps_index is only modify after adding succefully an opp, so
an OPP can't be missed.
> This is very messy and requires serious cleanup to be honest. Also it will be
> more preferred if armada_8k_add_opp() cleans up all the allocations it has done
> on a call if it fails in the middle of it, rather than a bigger routine freeing
> both successful and failed ones.
OK we can duplicate code for this if you prefer.
Thanks,
Gregory
>
>> + if (ret)
>> + goto remove_opp;
>> +
>> + opps_index++;
>> + cpumask_clear(&cpus);
>> + armada_8k_get_sharing_cpus(clk, &cpus);
>> + dev_pm_opp_set_sharing_cpus(cpu_dev, &cpus);
>> + }
>> +
>> + armada_8k_pdev = platform_device_register_simple("cpufreq-dt", -1,
>> + NULL, 0);
>> + ret = PTR_ERR_OR_ZERO(armada_8k_pdev);
>> + if (ret)
>> + goto remove_opp;
>> + return 0;
>> +
>> +remove_opp:
>> + armada_8k_cpufreq_free_table();
>> + return ret;
>> +}
>> +module_init(armada_8k_cpufreq_init);
>> +
>> +static void __exit armada_8k_cpufreq_exit(void)
>> +{
>> + armada_8k_cpufreq_free_table();
>> + platform_device_unregister(armada_8k_pdev);
>> +}
>> +module_exit(armada_8k_cpufreq_exit);
>> +
>> +MODULE_AUTHOR("Gregory Clement <gregory.clement@bootlin.com>");
>> +MODULE_DESCRIPTION("Armada 8K cpufreq driver");
>> +MODULE_LICENSE("GPL");
>> --
>> 2.19.2
>
> --
> viresh
--
Gregory Clement, Bootlin
Embedded Linux and Kernel engineering
http://bootlin.com
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next prev parent reply other threads:[~2018-12-18 14:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-11 16:42 [PATCH v3 0/2] Add cpufreq support for Armada 8K Gregory CLEMENT
2018-12-11 16:42 ` [PATCH v3 1/2] MAINTAINERS: add new entries for Armada 8K cpufreq driver Gregory CLEMENT
2018-12-11 16:42 ` [PATCH v3 2/2] cpufreq: ap806: add cpufreq driver for Armada 8K Gregory CLEMENT
2018-12-17 11:10 ` Viresh Kumar
2018-12-18 14:32 ` Gregory CLEMENT [this message]
2018-12-19 4:40 ` Viresh Kumar
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