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Message-ID: <20181121220614.GU22824@google.com>
Date: Wed, 21 Nov 2018 14:06:14 -0800
From: Matthias Kaehlcke <mka@...omium.org>
To: Taniya Das <tdas@...eaurora.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Viresh Kumar <viresh.kumar@...aro.org>,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
Stephen Boyd <sboyd@...nel.org>,
Rajendra Nayak <rnayak@...eaurora.org>,
devicetree@...r.kernel.org, robh@...nel.org,
skannan@...eaurora.org, linux-arm-msm@...r.kernel.org,
amit.kucheria@...aro.org, evgreen@...gle.com
Subject: Re: [PATCH v10 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq
HW driver
On Wed, Nov 21, 2018 at 04:12:47PM +0530, Taniya Das wrote:
> The CPUfreq HW present in some QCOM chipsets offloads the steps necessary
> for changing the frequency of CPUs. The driver implements the cpufreq
> driver interface for this hardware engine.
>
> Signed-off-by: Saravana Kannan <skannan@...eaurora.org>
> Signed-off-by: Taniya Das <tdas@...eaurora.org>
> ---
> drivers/cpufreq/Kconfig.arm | 11 ++
> drivers/cpufreq/Makefile | 1 +
> drivers/cpufreq/qcom-cpufreq-hw.c | 346 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 358 insertions(+)
> create mode 100644 drivers/cpufreq/qcom-cpufreq-hw.c
>
> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> index 4e1131e..688f102 100644
> --- a/drivers/cpufreq/Kconfig.arm
> +++ b/drivers/cpufreq/Kconfig.arm
> @@ -114,6 +114,17 @@ config ARM_QCOM_CPUFREQ_KRYO
>
> If in doubt, say N.
>
> +config ARM_QCOM_CPUFREQ_HW
> + tristate "QCOM CPUFreq HW driver"
> + depends on ARCH_QCOM || COMPILE_TEST
> + help
> + Support for the CPUFreq HW driver.
> + Some QCOM chipsets have a HW engine to offload the steps
> + necessary for changing the frequency of the CPUs. Firmware loaded
> + in this engine exposes a programming interface to the OS.
> + The driver implements the cpufreq interface for this HW engine.
> + Say Y if you want to support CPUFreq HW.
> +
> config ARM_S3C_CPUFREQ
> bool
> help
> diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
> index d5ee456..789b2e0 100644
> --- a/drivers/cpufreq/Makefile
> +++ b/drivers/cpufreq/Makefile
> @@ -62,6 +62,7 @@ obj-$(CONFIG_ARM_OMAP2PLUS_CPUFREQ) += omap-cpufreq.o
> obj-$(CONFIG_ARM_PXA2xx_CPUFREQ) += pxa2xx-cpufreq.o
> obj-$(CONFIG_PXA3xx) += pxa3xx-cpufreq.o
> obj-$(CONFIG_ARM_QCOM_CPUFREQ_KRYO) += qcom-cpufreq-kryo.o
> +obj-$(CONFIG_ARM_QCOM_CPUFREQ_HW) += qcom-cpufreq-hw.o
> obj-$(CONFIG_ARM_S3C2410_CPUFREQ) += s3c2410-cpufreq.o
> obj-$(CONFIG_ARM_S3C2412_CPUFREQ) += s3c2412-cpufreq.o
> obj-$(CONFIG_ARM_S3C2416_CPUFREQ) += s3c2416-cpufreq.o
> diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
> new file mode 100644
> index 0000000..6390e85
> --- /dev/null
> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
> @@ -0,0 +1,346 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2018, The Linux Foundation. All rights reserved.
> + */
> +
> +#include <linux/cpufreq.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/of_platform.h>
> +
> +#define LUT_MAX_ENTRIES 40U
> +#define CORE_COUNT_VAL(val) (((val) & (GENMASK(18, 16))) >> 16)
> +#define LUT_ROW_SIZE 32
> +#define CLK_HW_DIV 2
> +
> +/* Register offsets */
> +#define REG_ENABLE 0x0
> +#define REG_LUT_TABLE 0x110
> +#define REG_PERF_STATE 0x920
> +
> +struct cpufreq_qcom {
> + struct cpufreq_frequency_table *table;
> + void __iomem *perf_base;
> + cpumask_t related_cpus;
> + unsigned int max_cores;
> + unsigned long xo_rate;
> + unsigned long cpu_hw_rate;
> +};
> +
> +static struct cpufreq_qcom *qcom_freq_domain_map[NR_CPUS];
> +
> +static int
> +qcom_cpufreq_hw_target_index(struct cpufreq_policy *policy,
> + unsigned int index)
> +{
> + struct cpufreq_qcom *c = policy->driver_data;
> +
> + writel_relaxed(index, c->perf_base);
> +
> + return 0;
> +}
> +
> +static unsigned int qcom_cpufreq_hw_get(unsigned int cpu)
> +{
> + struct cpufreq_qcom *c;
> + struct cpufreq_policy *policy;
> + unsigned int index;
> +
> + policy = cpufreq_cpu_get_raw(cpu);
> + if (!policy)
> + return 0;
> +
> + c = policy->driver_data;
> +
> + index = readl_relaxed(c->perf_base);
> + index = min(index, LUT_MAX_ENTRIES - 1);
> +
> + return policy->freq_table[index].frequency;
> +}
> +
> +static unsigned int
> +qcom_cpufreq_hw_fast_switch(struct cpufreq_policy *policy,
> + unsigned int target_freq)
> +{
> + struct cpufreq_qcom *c = policy->driver_data;
> + int index;
> +
> + index = policy->cached_resolved_idx;
> + if (index < 0)
> + return 0;
> +
> + writel_relaxed(index, c->perf_base);
> +
> + return policy->freq_table[index].frequency;
> +}
> +
> +static int qcom_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
> +{
> + struct cpufreq_qcom *c;
> +
> + c = qcom_freq_domain_map[policy->cpu];
> + if (!c) {
> + pr_err("No scaling support for CPU%d\n", policy->cpu);
> + return -ENODEV;
> + }
> +
> + cpumask_copy(policy->cpus, &c->related_cpus);
> +
> + policy->fast_switch_possible = true;
> + policy->freq_table = c->table;
> + policy->driver_data = c;
> +
> + return 0;
> +}
> +
> +static struct freq_attr *qcom_cpufreq_hw_attr[] = {
> + &cpufreq_freq_attr_scaling_available_freqs,
> + &cpufreq_freq_attr_scaling_boost_freqs,
> + NULL
> +};
> +
> +static struct cpufreq_driver cpufreq_qcom_hw_driver = {
> + .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK |
> + CPUFREQ_HAVE_GOVERNOR_PER_POLICY,
> + .verify = cpufreq_generic_frequency_table_verify,
> + .target_index = qcom_cpufreq_hw_target_index,
> + .get = qcom_cpufreq_hw_get,
> + .init = qcom_cpufreq_hw_cpu_init,
> + .fast_switch = qcom_cpufreq_hw_fast_switch,
> + .name = "qcom-cpufreq-hw",
> + .attr = qcom_cpufreq_hw_attr,
> + .boost_enabled = true,
I have no real expertise with cpufreq boost, but after reading a bit
through cpufreq code this seems wrong. Boost is enabled statically,
however the driver has neither a ->set_boost function nor does it call
cpufreq_enable_boost_support() which would use a default
implementation for ->set_boost. As a result boost support is
effectively disabled:
static bool cpufreq_boost_supported(void)
{
return likely(cpufreq_driver) && cpufreq_driver->set_boost;
}
The driver should probably do the same as cpufreq-dt.c and call
cpufreq_enable_boost_support() if boost frequencies are available,
instead of 'enabling' boost statically.
Thanks
Matthias
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