Re: [PATCH v5 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq HW driver
From: Taniya Das
Date: Tue Jul 17 2018 - 01:57:42 EST
Hello Matthias,
Thanks for your review comments.
On 7/13/2018 5:49 AM, Matthias Kaehlcke wrote:
Hi,
On Thu, Jul 12, 2018 at 11:35:45PM +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@xxxxxxxxxxxxxx>
Signed-off-by: Taniya Das <tdas@xxxxxxxxxxxxxx>
---
drivers/cpufreq/Kconfig.arm | 10 ++
drivers/cpufreq/Makefile | 1 +
drivers/cpufreq/qcom-cpufreq-hw.c | 344 ++++++++++++++++++++++++++++++++++++++
3 files changed, 355 insertions(+)
create mode 100644 drivers/cpufreq/qcom-cpufreq-hw.c
diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 52f5f1a..141ec3e 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -312,3 +312,13 @@ config ARM_PXA2xx_CPUFREQ
This add the CPUFreq driver support for Intel PXA2xx SOCs.
If in doubt, say N.
+
+config ARM_QCOM_CPUFREQ_HW
+ bool "QCOM CPUFreq HW driver"
+ 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 interafce to the High-level OS.
+ The driver implements the cpufreq driver interface for this HW engine.
+ Say Y if you want to support CPUFreq HW.
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index fb4a2ec..1226a3e 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -86,6 +86,7 @@ obj-$(CONFIG_ARM_TEGRA124_CPUFREQ) += tegra124-cpufreq.o
obj-$(CONFIG_ARM_TEGRA186_CPUFREQ) += tegra186-cpufreq.o
obj-$(CONFIG_ARM_TI_CPUFREQ) += ti-cpufreq.o
obj-$(CONFIG_ARM_VEXPRESS_SPC_CPUFREQ) += vexpress-spc-cpufreq.o
+obj-$(CONFIG_ARM_QCOM_CPUFREQ_HW) += qcom-cpufreq-hw.o
##################################################################################
diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
new file mode 100644
index 0000000..fa25a95
--- /dev/null
+++ b/drivers/cpufreq/qcom-cpufreq-hw.c
@@ -0,0 +1,344 @@
+// 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 INIT_RATE 300000000UL
+#define XO_RATE 19200000UL
+#define LUT_MAX_ENTRIES 40U
+#define CORE_COUNT_VAL(val) (((val) & (GENMASK(18, 16))) >> 16)
+#define LUT_ROW_SIZE 32
+
+enum {
+ REG_ENABLE,
+ REG_LUT_TABLE,
+ REG_PERF_STATE,
+
+ REG_ARRAY_SIZE,
+};
+
+struct cpufreq_qcom {
+ struct cpufreq_frequency_table *table;
+ struct device *dev;
+ const u16 *reg_offset;
+ void __iomem *base;
+ cpumask_t related_cpus;
+ unsigned int max_cores;
Same comment as on v4:
Why *max*_cores? This seems to be the number of CPUs in a cluster and
qcom_read_lut() expects the core count read from the LUT to match
exactly. Maybe it's the name from the datasheet? Should it still be
'num_cores' or similer?
Your understanding is correct. I would prefer to leave the naming as
'max_cores'.
+static struct cpufreq_qcom *qcom_freq_domain_map[NR_CPUS];
It would be an option to limit this to the number of CPU clusters and
allocate it dynamically when the driver is initialized (key = first
core in the cluster). Probably not worth the hassle with the limited
number of cores though.
+static int qcom_read_lut(struct platform_device *pdev,
+ struct cpufreq_qcom *c)
+{
+ struct device *dev = &pdev->dev;
+ unsigned int offset;
+ u32 data, src, lval, i, core_count, prev_cc, prev_freq, cur_freq;
+
+ c->table = devm_kcalloc(dev, LUT_MAX_ENTRIES + 1,
+ sizeof(*c->table), GFP_KERNEL);
+ if (!c->table)
+ return -ENOMEM;
+
+ offset = c->reg_offset[REG_LUT_TABLE];
+
+ for (i = 0; i < LUT_MAX_ENTRIES; i++) {
+ data = readl_relaxed(c->base + offset + i * LUT_ROW_SIZE);
+ src = ((data & GENMASK(31, 30)) >> 30);
+ lval = (data & GENMASK(7, 0));
+ core_count = CORE_COUNT_VAL(data);
+
+ if (src == 0)
+ c->table[i].frequency = INIT_RATE / 1000;
+ else
+ c->table[i].frequency = XO_RATE * lval / 1000;
You changed the condition from '!src' to 'src == 0'. My suggestion on
v4 was in part about a negative condition, but also about the
order. If it doesn't obstruct the code otherwise I think for an if-else
branch it is good practice to handle the more common case first and
then the 'exception'. I would expect most entries to have an actual
rate. Just a nit in any case, feel free to ignore if you prefer as is.
Thanks, Sure, I would take care of it in the next series.
+static int qcom_cpu_resources_init(struct platform_device *pdev,
+ struct device_node *np, unsigned int cpu)
+{
+ struct cpufreq_qcom *c;
+ struct resource res;
+ struct device *dev = &pdev->dev;
+ unsigned int offset, cpu_r;
+ int ret;
+
+ c = devm_kzalloc(dev, sizeof(*c), GFP_KERNEL);
+ if (!c)
+ return -ENOMEM;
+
+ c->reg_offset = of_device_get_match_data(&pdev->dev);
+ if (!c->reg_offset)
+ return -EINVAL;
+
+ if (of_address_to_resource(np, 0, &res))
+ return -ENOMEM;
+
+ c->base = devm_ioremap(dev, res.start, resource_size(&res));
+ if (!c->base) {
+ dev_err(dev, "Unable to map %s base\n", np->name);
+ return -ENOMEM;
+ }
+
+ offset = c->reg_offset[REG_ENABLE];
+
+ /* HW should be in enabled state to proceed */
+ if (!(readl_relaxed(c->base + offset) & 0x1)) {
+ dev_err(dev, "%s cpufreq hardware not enabled\n", np->name);
+ return -ENODEV;
+ }
+
+ ret = qcom_get_related_cpus(np, &c->related_cpus);
+ if (ret) {
+ dev_err(dev, "%s failed to get related CPUs\n", np->name);
+ return ret;
+ }
+
+ c->max_cores = cpumask_weight(&c->related_cpus);
+ if (!c->max_cores)
+ return -ENOENT;
+
+ ret = qcom_read_lut(pdev, c);
+ if (ret) {
+ dev_err(dev, "%s failed to read LUT\n", np->name);
+ return ret;
+ }
+
+ qcom_freq_domain_map[cpu] = c;
If the general code structure remains as is (see my comment below)
the assignment could be done in a 'if (cpu == cpu_r)' branch instead
of first assigning and then overwriting it for 'cpu != cpu_r'.
+
+ /* Related CPUs to keep a single copy */
+ cpu_r = cpumask_first(&c->related_cpus);
+ if (cpu != cpu_r) {
+ qcom_freq_domain_map[cpu] = qcom_freq_domain_map[cpu_r];
+ devm_kfree(dev, c);
+ }
Couldn't we do this at the beginning of the function instead of going
through allocation, ioremap, read_lut for every core only to throw the
information away later for the 'related' CPUs?
qcom_cpu_resources_init() is called with increasing 'cpu' values, hence the
'first' CPU of the cluster is already initialized when the 'related'
ones are processed.
I would be moving the code to the beginning of the function.
+ return 0;
+}
+
+static int qcom_resources_init(struct platform_device *pdev)
+{
+ struct device_node *np, *cpu_np;
+ unsigned int cpu;
+ int ret;
+
+ for_each_possible_cpu(cpu) {
+ cpu_np = of_cpu_device_node_get(cpu);
+ if (!cpu_np) {
+ dev_err(&pdev->dev, "Failed to get cpu %d device\n",
+ cpu);
+ continue;
+ }
+
+ np = of_parse_phandle(cpu_np, "qcom,freq-domain", 0);
+ if (!np) {
+ dev_err(&pdev->dev, "Failed to get freq-domain device\n");
of_node_put(cpu_np);
+ return -EINVAL;
+ }
+
+ of_node_put(cpu_np);
+
+ ret = qcom_cpu_resources_init(pdev, np, cpu);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
Thanks
Matthias
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