diff mbox series

[TEGRA194_CPUFREQ,v2,2/3] cpufreq: Add Tegra194 cpufreq driver

Message ID 1586028547-14993-3-git-send-email-sumitg@nvidia.com
State New
Headers show
Series Add cpufreq driver for Tegra194 | expand

Commit Message

Sumit Gupta April 4, 2020, 7:29 p.m. UTC
Add support for CPU frequency scaling on Tegra194. The frequency
of each core can be adjusted by writing a clock divisor value to
an MSR on the core. The range of valid divisors is queried from
the BPMP.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
---
 drivers/cpufreq/Kconfig.arm        |   6 +
 drivers/cpufreq/Makefile           |   1 +
 drivers/cpufreq/tegra194-cpufreq.c | 412 +++++++++++++++++++++++++++++++++++++
 3 files changed, 419 insertions(+)
 create mode 100644 drivers/cpufreq/tegra194-cpufreq.c

Comments

Dmitry Osipenko April 5, 2020, 2:05 p.m. UTC | #1
04.04.2020 22:29, Sumit Gupta пишет:
...
> +static void tegra_read_counters(struct work_struct *work)
> +{
> +	struct read_counters_work *read_counters_work;
> +	struct tegra_cpu_ctr *c;
> +	u64 val;
> +
> +	/*
> +	 * ref_clk_counter(32 bit counter) runs on constant clk,
> +	 * pll_p(408MHz).
> +	 * It will take = 2 ^ 32 / 408 MHz to overflow ref clk counter
> +	 *              = 10526880 usec = 10.527 sec to overflow
> +	 *
> +	 * Like wise core_clk_counter(32 bit counter) runs on core clock.
> +	 * It's synchronized to crab_clk (cpu_crab_clk) which runs at
> +	 * freq of cluster. Assuming max cluster clock ~2000MHz,
> +	 * It will take = 2 ^ 32 / 2000 MHz to overflow core clk counter
> +	 *              = ~2.147 sec to overflow
> +	 */
> +	read_counters_work = container_of(work, struct read_counters_work,
> +					  work);
> +	c = &read_counters_work->c;
> +
> +	val = read_freq_feedback();
> +	c->last_refclk_cnt = lower_32_bits(val);
> +	c->last_coreclk_cnt = upper_32_bits(val);
> +	udelay(c->delay);
> +	val = read_freq_feedback();
> +	c->refclk_cnt = lower_32_bits(val);
> +	c->coreclk_cnt = upper_32_bits(val);
> +}
> +
> +/*
> + * Return instantaneous cpu speed
> + * Instantaneous freq is calculated as -
> + * -Takes sample on every query of getting the freq.
> + *	- Read core and ref clock counters;
> + *	- Delay for X us
> + *	- Read above cycle counters again
> + *	- Calculates freq by subtracting current and previous counters
> + *	  divided by the delay time or eqv. of ref_clk_counter in delta time
> + *	- Return Kcycles/second, freq in KHz
> + *
> + *	delta time period = x sec
> + *			  = delta ref_clk_counter / (408 * 10^6) sec
> + *	freq in Hz = cycles/sec
> + *		   = (delta cycles / x sec
> + *		   = (delta cycles * 408 * 10^6) / delta ref_clk_counter
> + *	in KHz	   = (delta cycles * 408 * 10^3) / delta ref_clk_counter
> + *
> + * @cpu - logical cpu whose freq to be updated


> + * Returns freq in KHz on success, 0 if cpu is offline

I don't see any checks in the code about whether CPU is offline.

Googling for "queue_work_on offline cpu" suggests that this function
should hang.

> + */
> +static unsigned int tegra194_get_speed_common(u32 cpu, u32 delay)
> +{
> +	struct read_counters_work read_counters_work;
> +	struct tegra_cpu_ctr c;
> +	u32 delta_refcnt;
> +	u32 delta_ccnt;
> +	u32 rate_mhz;
> +
> +	read_counters_work.c.cpu = cpu;
> +	read_counters_work.c.delay = delay;
> +	INIT_WORK_ONSTACK(&read_counters_work.work, tegra_read_counters);
> +	queue_work_on(cpu, read_counters_wq, &read_counters_work.work);
> +	flush_work(&read_counters_work.work);
> +	c = read_counters_work.c;
> +
> +	if (c.coreclk_cnt < c.last_coreclk_cnt)
> +		delta_ccnt = c.coreclk_cnt + (MAX_CNT - c.last_coreclk_cnt);
> +	else
> +		delta_ccnt = c.coreclk_cnt - c.last_coreclk_cnt;
> +	if (!delta_ccnt)
> +		return 0;
> +
> +	/* ref clock is 32 bits */
> +	if (c.refclk_cnt < c.last_refclk_cnt)
> +		delta_refcnt = c.refclk_cnt + (MAX_CNT - c.last_refclk_cnt);
> +	else
> +		delta_refcnt = c.refclk_cnt - c.last_refclk_cnt;
> +	if (!delta_refcnt) {
> +		pr_debug("cpufreq: %d is idle, delta_refcnt: 0\n", cpu);
> +		return 0;
> +	}
> +	rate_mhz = ((unsigned long)(delta_ccnt * REF_CLK_MHZ)) / delta_refcnt;
> +
> +	return (rate_mhz * KHZ); /* in KHz */
> +}
Dmitry Osipenko April 5, 2020, 2:11 p.m. UTC | #2
04.04.2020 22:29, Sumit Gupta пишет:
...
> +static void tegra_read_counters(struct work_struct *work)
> +{
> +	struct read_counters_work *read_counters_work;
> +	struct tegra_cpu_ctr *c;
> +	u64 val;
> +
> +	/*
> +	 * ref_clk_counter(32 bit counter) runs on constant clk,
> +	 * pll_p(408MHz).

Is changing PLLP rate really impossible on T194? What makes you say that
it runs on a fixed 408MHz?
Sumit Gupta April 7, 2020, 6:55 p.m. UTC | #3
On 05/04/20 7:35 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
> 
> 
> 04.04.2020 22:29, Sumit Gupta пишет:
> ...
>> +static void tegra_read_counters(struct work_struct *work)
>> +{
>> +     struct read_counters_work *read_counters_work;
>> +     struct tegra_cpu_ctr *c;
>> +     u64 val;
>> +
>> +     /*
>> +      * ref_clk_counter(32 bit counter) runs on constant clk,
>> +      * pll_p(408MHz).
>> +      * It will take = 2 ^ 32 / 408 MHz to overflow ref clk counter
>> +      *              = 10526880 usec = 10.527 sec to overflow
>> +      *
>> +      * Like wise core_clk_counter(32 bit counter) runs on core clock.
>> +      * It's synchronized to crab_clk (cpu_crab_clk) which runs at
>> +      * freq of cluster. Assuming max cluster clock ~2000MHz,
>> +      * It will take = 2 ^ 32 / 2000 MHz to overflow core clk counter
>> +      *              = ~2.147 sec to overflow
>> +      */
>> +     read_counters_work = container_of(work, struct read_counters_work,
>> +                                       work);
>> +     c = &read_counters_work->c;
>> +
>> +     val = read_freq_feedback();
>> +     c->last_refclk_cnt = lower_32_bits(val);
>> +     c->last_coreclk_cnt = upper_32_bits(val);
>> +     udelay(c->delay);
>> +     val = read_freq_feedback();
>> +     c->refclk_cnt = lower_32_bits(val);
>> +     c->coreclk_cnt = upper_32_bits(val);
>> +}
>> +
>> +/*
>> + * Return instantaneous cpu speed
>> + * Instantaneous freq is calculated as -
>> + * -Takes sample on every query of getting the freq.
>> + *   - Read core and ref clock counters;
>> + *   - Delay for X us
>> + *   - Read above cycle counters again
>> + *   - Calculates freq by subtracting current and previous counters
>> + *     divided by the delay time or eqv. of ref_clk_counter in delta time
>> + *   - Return Kcycles/second, freq in KHz
>> + *
>> + *   delta time period = x sec
>> + *                     = delta ref_clk_counter / (408 * 10^6) sec
>> + *   freq in Hz = cycles/sec
>> + *              = (delta cycles / x sec
>> + *              = (delta cycles * 408 * 10^6) / delta ref_clk_counter
>> + *   in KHz     = (delta cycles * 408 * 10^3) / delta ref_clk_counter
>> + *
>> + * @cpu - logical cpu whose freq to be updated
> 
> 
>> + * Returns freq in KHz on success, 0 if cpu is offline
> 
> I don't see any checks in the code about whether CPU is offline.
> 
> Googling for "queue_work_on offline cpu" suggests that this function
> should hang.
> 
Tried this and didn't get crash or hang.
show_cpuinfo_cur_freq() returns "<unknown>" value on reading frequency 
from a cluster having both it's cores offline.
If only one cpu is offline, then frequency of other online cpu which is 
managing the policy of that cluster is returned.
Have still added below check as guard in get|set() freq calls.
	if (!cpu_online(cpu))
		return -EINVAL;
Thankyou for the input.

>> + */
>> +static unsigned int tegra194_get_speed_common(u32 cpu, u32 delay)
>> +{
>> +     struct read_counters_work read_counters_work;
>> +     struct tegra_cpu_ctr c;
>> +     u32 delta_refcnt;
>> +     u32 delta_ccnt;
>> +     u32 rate_mhz;
>> +
>> +     read_counters_work.c.cpu = cpu;
>> +     read_counters_work.c.delay = delay;
>> +     INIT_WORK_ONSTACK(&read_counters_work.work, tegra_read_counters);
>> +     queue_work_on(cpu, read_counters_wq, &read_counters_work.work);
>> +     flush_work(&read_counters_work.work);
>> +     c = read_counters_work.c;
>> +
>> +     if (c.coreclk_cnt < c.last_coreclk_cnt)
>> +             delta_ccnt = c.coreclk_cnt + (MAX_CNT - c.last_coreclk_cnt);
>> +     else
>> +             delta_ccnt = c.coreclk_cnt - c.last_coreclk_cnt;
>> +     if (!delta_ccnt)
>> +             return 0;
>> +
>> +     /* ref clock is 32 bits */
>> +     if (c.refclk_cnt < c.last_refclk_cnt)
>> +             delta_refcnt = c.refclk_cnt + (MAX_CNT - c.last_refclk_cnt);
>> +     else
>> +             delta_refcnt = c.refclk_cnt - c.last_refclk_cnt;
>> +     if (!delta_refcnt) {
>> +             pr_debug("cpufreq: %d is idle, delta_refcnt: 0\n", cpu);
>> +             return 0;
>> +     }
>> +     rate_mhz = ((unsigned long)(delta_ccnt * REF_CLK_MHZ)) / delta_refcnt;
>> +
>> +     return (rate_mhz * KHZ); /* in KHz */
>> +}
>
Sumit Gupta April 7, 2020, 6:56 p.m. UTC | #4
On 05/04/20 7:41 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
> 
> 
> 04.04.2020 22:29, Sumit Gupta пишет:
> ...
>> +static void tegra_read_counters(struct work_struct *work)
>> +{
>> +     struct read_counters_work *read_counters_work;
>> +     struct tegra_cpu_ctr *c;
>> +     u64 val;
>> +
>> +     /*
>> +      * ref_clk_counter(32 bit counter) runs on constant clk,
>> +      * pll_p(408MHz).
> 
> Is changing PLLP rate really impossible on T194? What makes you say that
> it runs on a fixed 408MHz?
> 
Pasting below from TRM.
Register "NVFREQ_FEEDBACK_EL1":
....
[31:0] PLLP counter: This counter counts at a fixed frequency (408 MHz).
Dmitry Osipenko April 7, 2020, 7:12 p.m. UTC | #5
07.04.2020 21:55, sumitg пишет:
...
>>> + * Returns freq in KHz on success, 0 if cpu is offline
>>
>> I don't see any checks in the code about whether CPU is offline.
>>
>> Googling for "queue_work_on offline cpu" suggests that this function
>> should hang.
>>
> Tried this and didn't get crash or hang.
> show_cpuinfo_cur_freq() returns "<unknown>" value on reading frequency
> from a cluster having both it's cores offline.
> If only one cpu is offline, then frequency of other online cpu which is
> managing the policy of that cluster is returned.
> Have still added below check as guard in get|set() freq calls.
>     if (!cpu_online(cpu))
>         return -EINVAL;
> Thankyou for the input.

If CPUFreq core takes care of taking into account the offline CPU, then
the check isn't needed. It also wouldn't be enough if there was a
problem here.
diff mbox series

Patch

diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index a905796..4bcd47c 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -320,6 +320,12 @@  config ARM_TEGRA186_CPUFREQ
 	help
 	  This adds the CPUFreq driver support for Tegra186 SOCs.
 
+config ARM_TEGRA194_CPUFREQ
+	tristate "Tegra194 CPUFreq support"
+	depends on ARCH_TEGRA && TEGRA_BPMP
+	help
+	  This adds CPU frequency driver support for Tegra194 SOCs.
+
 config ARM_TI_CPUFREQ
 	bool "Texas Instruments CPUFreq support"
 	depends on ARCH_OMAP2PLUS
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 9a9f5cc..433d492 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -85,6 +85,7 @@  obj-$(CONFIG_ARM_TANGO_CPUFREQ)		+= tango-cpufreq.o
 obj-$(CONFIG_ARM_TEGRA20_CPUFREQ)	+= tegra20-cpufreq.o
 obj-$(CONFIG_ARM_TEGRA124_CPUFREQ)	+= tegra124-cpufreq.o
 obj-$(CONFIG_ARM_TEGRA186_CPUFREQ)	+= tegra186-cpufreq.o
+obj-$(CONFIG_ARM_TEGRA194_CPUFREQ)	+= tegra194-cpufreq.o
 obj-$(CONFIG_ARM_TI_CPUFREQ)		+= ti-cpufreq.o
 obj-$(CONFIG_ARM_VEXPRESS_SPC_CPUFREQ)	+= vexpress-spc-cpufreq.o
 
diff --git a/drivers/cpufreq/tegra194-cpufreq.c b/drivers/cpufreq/tegra194-cpufreq.c
new file mode 100644
index 0000000..76f8d0a
--- /dev/null
+++ b/drivers/cpufreq/tegra194-cpufreq.c
@@ -0,0 +1,412 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2019, NVIDIA CORPORATION. All rights reserved
+ */
+
+#include <linux/cpu.h>
+#include <linux/cpufreq.h>
+#include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include <asm/smp_plat.h>
+
+#include <soc/tegra/bpmp.h>
+#include <soc/tegra/bpmp-abi.h>
+
+#define KHZ                     1000
+#define REF_CLK_MHZ             408 /* 408 MHz */
+#define US_DELAY                2000
+#define US_DELAY_MIN            2
+#define CPUFREQ_TBL_STEP_HZ     (50 * KHZ * KHZ)
+#define MAX_CNT                 ~0U
+
+/* cpufreq transisition latency */
+#define TEGRA_CPUFREQ_TRANSITION_LATENCY (300 * 1000) /* unit in nanoseconds */
+
+enum cluster {
+	CLUSTER0,
+	CLUSTER1,
+	CLUSTER2,
+	CLUSTER3,
+	MAX_CLUSTERS,
+};
+
+struct tegra194_cpufreq_data {
+	void __iomem *regs;
+	size_t num_clusters;
+	struct cpufreq_frequency_table **tables;
+};
+
+struct tegra_cpu_ctr {
+	u32 cpu;
+	u32 delay;
+	u32 coreclk_cnt, last_coreclk_cnt;
+	u32 refclk_cnt, last_refclk_cnt;
+};
+
+static struct workqueue_struct *read_counters_wq;
+struct read_counters_work {
+	struct work_struct work;
+	struct tegra_cpu_ctr c;
+};
+
+static enum cluster get_cpu_cluster(u8 cpu)
+{
+	return MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
+}
+
+/*
+ * Read per-core Read-only system register NVFREQ_FEEDBACK_EL1.
+ * The register provides frequency feedback information to
+ * determine the average actual frequency a core has run at over
+ * a period of time.
+ *	[31:0] PLLP counter: Counts at fixed frequency (408 MHz)
+ *	[63:32] Core clock counter: counts on every core clock cycle
+ *			where the core is architecturally clocking
+ */
+static u64 read_freq_feedback(void)
+{
+	u64 val = 0;
+
+	asm volatile("mrs %0, s3_0_c15_c0_5" : "=r" (val) : );
+
+	return val;
+}
+
+u16 map_freq_to_ndiv(struct mrq_cpu_ndiv_limits_response *nltbl, u32 freq)
+{
+	return DIV_ROUND_UP(freq * nltbl->pdiv * nltbl->mdiv,
+			    nltbl->ref_clk_hz / KHZ);
+}
+
+static inline u32 map_ndiv_to_freq(struct mrq_cpu_ndiv_limits_response
+				   *nltbl, u16 ndiv)
+{
+	return nltbl->ref_clk_hz / KHZ * ndiv / (nltbl->pdiv * nltbl->mdiv);
+}
+
+static void tegra_read_counters(struct work_struct *work)
+{
+	struct read_counters_work *read_counters_work;
+	struct tegra_cpu_ctr *c;
+	u64 val;
+
+	/*
+	 * ref_clk_counter(32 bit counter) runs on constant clk,
+	 * pll_p(408MHz).
+	 * It will take = 2 ^ 32 / 408 MHz to overflow ref clk counter
+	 *              = 10526880 usec = 10.527 sec to overflow
+	 *
+	 * Like wise core_clk_counter(32 bit counter) runs on core clock.
+	 * It's synchronized to crab_clk (cpu_crab_clk) which runs at
+	 * freq of cluster. Assuming max cluster clock ~2000MHz,
+	 * It will take = 2 ^ 32 / 2000 MHz to overflow core clk counter
+	 *              = ~2.147 sec to overflow
+	 */
+	read_counters_work = container_of(work, struct read_counters_work,
+					  work);
+	c = &read_counters_work->c;
+
+	val = read_freq_feedback();
+	c->last_refclk_cnt = lower_32_bits(val);
+	c->last_coreclk_cnt = upper_32_bits(val);
+	udelay(c->delay);
+	val = read_freq_feedback();
+	c->refclk_cnt = lower_32_bits(val);
+	c->coreclk_cnt = upper_32_bits(val);
+}
+
+/*
+ * Return instantaneous cpu speed
+ * Instantaneous freq is calculated as -
+ * -Takes sample on every query of getting the freq.
+ *	- Read core and ref clock counters;
+ *	- Delay for X us
+ *	- Read above cycle counters again
+ *	- Calculates freq by subtracting current and previous counters
+ *	  divided by the delay time or eqv. of ref_clk_counter in delta time
+ *	- Return Kcycles/second, freq in KHz
+ *
+ *	delta time period = x sec
+ *			  = delta ref_clk_counter / (408 * 10^6) sec
+ *	freq in Hz = cycles/sec
+ *		   = (delta cycles / x sec
+ *		   = (delta cycles * 408 * 10^6) / delta ref_clk_counter
+ *	in KHz	   = (delta cycles * 408 * 10^3) / delta ref_clk_counter
+ *
+ * @cpu - logical cpu whose freq to be updated
+ * Returns freq in KHz on success, 0 if cpu is offline
+ */
+static unsigned int tegra194_get_speed_common(u32 cpu, u32 delay)
+{
+	struct read_counters_work read_counters_work;
+	struct tegra_cpu_ctr c;
+	u32 delta_refcnt;
+	u32 delta_ccnt;
+	u32 rate_mhz;
+
+	read_counters_work.c.cpu = cpu;
+	read_counters_work.c.delay = delay;
+	INIT_WORK_ONSTACK(&read_counters_work.work, tegra_read_counters);
+	queue_work_on(cpu, read_counters_wq, &read_counters_work.work);
+	flush_work(&read_counters_work.work);
+	c = read_counters_work.c;
+
+	if (c.coreclk_cnt < c.last_coreclk_cnt)
+		delta_ccnt = c.coreclk_cnt + (MAX_CNT - c.last_coreclk_cnt);
+	else
+		delta_ccnt = c.coreclk_cnt - c.last_coreclk_cnt;
+	if (!delta_ccnt)
+		return 0;
+
+	/* ref clock is 32 bits */
+	if (c.refclk_cnt < c.last_refclk_cnt)
+		delta_refcnt = c.refclk_cnt + (MAX_CNT - c.last_refclk_cnt);
+	else
+		delta_refcnt = c.refclk_cnt - c.last_refclk_cnt;
+	if (!delta_refcnt) {
+		pr_debug("cpufreq: %d is idle, delta_refcnt: 0\n", cpu);
+		return 0;
+	}
+	rate_mhz = ((unsigned long)(delta_ccnt * REF_CLK_MHZ)) / delta_refcnt;
+
+	return (rate_mhz * KHZ); /* in KHz */
+}
+
+static unsigned int tegra194_get_speed(u32 cpu)
+{
+	return tegra194_get_speed_common(cpu, US_DELAY);
+}
+
+static unsigned int tegra194_fast_get_speed(u32 cpu)
+{
+	return tegra194_get_speed_common(cpu, US_DELAY_MIN);
+}
+
+static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
+{
+	struct tegra194_cpufreq_data *data = cpufreq_get_driver_data();
+	int cluster = get_cpu_cluster(policy->cpu);
+
+	if (cluster >= data->num_clusters)
+		return -EINVAL;
+
+	policy->cur = tegra194_fast_get_speed(policy->cpu); /* boot freq */
+
+	/* set same policy for all cpus */
+	cpumask_copy(policy->cpus, cpu_possible_mask);
+
+	policy->freq_table = data->tables[cluster];
+	policy->cpuinfo.transition_latency = TEGRA_CPUFREQ_TRANSITION_LATENCY;
+
+	return 0;
+}
+
+static void set_cpu_ndiv(void *data)
+{
+	struct cpufreq_frequency_table *tbl = data;
+	u64 ndiv_val = (u64)tbl->driver_data;
+
+	asm volatile("msr s3_0_c15_c0_4, %0" : : "r" (ndiv_val));
+}
+
+static int tegra194_cpufreq_set_target(struct cpufreq_policy *policy,
+				       unsigned int index)
+{
+	struct cpufreq_frequency_table *tbl = policy->freq_table + index;
+
+	on_each_cpu_mask(policy->cpus, set_cpu_ndiv, tbl, true);
+
+	return 0;
+}
+
+static struct cpufreq_driver tegra194_cpufreq_driver = {
+	.name = "tegra194",
+	.flags = CPUFREQ_STICKY | CPUFREQ_CONST_LOOPS |
+		CPUFREQ_NEED_INITIAL_FREQ_CHECK,
+	.verify = cpufreq_generic_frequency_table_verify,
+	.target_index = tegra194_cpufreq_set_target,
+	.get = tegra194_get_speed,
+	.init = tegra194_cpufreq_init,
+	.attr = cpufreq_generic_attr,
+};
+
+static void tegra194_cpufreq_free_resources(void)
+{
+	flush_workqueue(read_counters_wq);
+	destroy_workqueue(read_counters_wq);
+}
+
+static struct cpufreq_frequency_table *
+init_freq_table(struct platform_device *pdev, struct tegra_bpmp *bpmp,
+		unsigned int cluster_id)
+{
+	struct cpufreq_frequency_table *freq_table;
+	struct mrq_cpu_ndiv_limits_response resp;
+	unsigned int num_freqs, ndiv, delta_ndiv;
+	struct mrq_cpu_ndiv_limits_request req;
+	struct tegra_bpmp_message msg;
+	u16 freq_table_step_size;
+	int err, index;
+
+	memset(&req, 0, sizeof(req));
+	req.cluster_id = cluster_id;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.mrq = MRQ_CPU_NDIV_LIMITS;
+	msg.tx.data = &req;
+	msg.tx.size = sizeof(req);
+	msg.rx.data = &resp;
+	msg.rx.size = sizeof(resp);
+
+	err = tegra_bpmp_transfer(bpmp, &msg);
+	if (err)
+		return ERR_PTR(err);
+
+	/*
+	 * Make sure frequency table step is a multiple of mdiv to match
+	 * vhint table granularity.
+	 */
+	freq_table_step_size = resp.mdiv *
+			DIV_ROUND_UP(CPUFREQ_TBL_STEP_HZ, resp.ref_clk_hz);
+
+	dev_dbg(&pdev->dev, "cluster %d: frequency table step size: %d\n",
+		cluster_id, freq_table_step_size);
+
+	delta_ndiv = resp.ndiv_max - resp.ndiv_min;
+
+	if (unlikely(delta_ndiv == 0))
+		num_freqs = 1;
+	else
+		/* We store both ndiv_min and ndiv_max hence the +1 */
+		num_freqs = delta_ndiv / freq_table_step_size + 1;
+
+	num_freqs += (delta_ndiv % freq_table_step_size) ? 1 : 0;
+
+	freq_table = devm_kcalloc(&pdev->dev, num_freqs + 1,
+				  sizeof(*freq_table), GFP_KERNEL);
+	if (!freq_table)
+		return ERR_PTR(-ENOMEM);
+
+	for (index = 0, ndiv = resp.ndiv_min;
+			ndiv < resp.ndiv_max;
+			index++, ndiv += freq_table_step_size) {
+		freq_table[index].driver_data = ndiv;
+		freq_table[index].frequency = map_ndiv_to_freq(&resp, ndiv);
+	}
+
+	freq_table[index].driver_data = resp.ndiv_max;
+	freq_table[index++].frequency = map_ndiv_to_freq(&resp, resp.ndiv_max);
+	freq_table[index].frequency = CPUFREQ_TABLE_END;
+
+	return freq_table;
+}
+
+static int tegra194_cpufreq_probe(struct platform_device *pdev)
+{
+	struct tegra194_cpufreq_data *data;
+	struct tegra_bpmp *bpmp;
+	int err, i;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->num_clusters = MAX_CLUSTERS;
+	data->tables = devm_kcalloc(&pdev->dev, data->num_clusters,
+				    sizeof(*data->tables), GFP_KERNEL);
+	if (!data->tables)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, data);
+
+	read_counters_wq = alloc_workqueue("read_counters_wq", __WQ_LEGACY, 1);
+	if (!read_counters_wq) {
+		dev_err(&pdev->dev, "fail to create_workqueue\n");
+		return -EINVAL;
+	}
+
+	bpmp = of_tegra_bpmp_get();
+	if (IS_ERR(bpmp)) {
+		err = PTR_ERR(bpmp);
+		goto err_free_res;
+	}
+
+	for (i = 0; i < data->num_clusters; i++) {
+		data->tables[i] = init_freq_table(pdev, bpmp, i);
+		if (IS_ERR(data->tables[i])) {
+			err = PTR_ERR(data->tables[i]);
+			goto put_bpmp;
+		}
+	}
+
+	tegra_bpmp_put(bpmp);
+
+	tegra194_cpufreq_driver.driver_data = data;
+
+	err = cpufreq_register_driver(&tegra194_cpufreq_driver);
+	if (err)
+		goto err_free_res;
+
+	return err;
+
+put_bpmp:
+	tegra_bpmp_put(bpmp);
+err_free_res:
+	tegra194_cpufreq_free_resources();
+	return err;
+}
+
+static int tegra194_cpufreq_remove(struct platform_device *pdev)
+{
+	cpufreq_unregister_driver(&tegra194_cpufreq_driver);
+	tegra194_cpufreq_free_resources();
+
+	return 0;
+}
+
+static struct platform_driver tegra194_cpufreq_platform_driver = {
+	.driver = {
+		.name = "tegra194-cpufreq",
+	},
+	.probe = tegra194_cpufreq_probe,
+	.remove = tegra194_cpufreq_remove,
+};
+
+static int __init tegra_cpufreq_init(void)
+{
+	struct platform_device *pdev;
+	int ret;
+
+	if (!of_machine_is_compatible("nvidia,tegra194"))
+		return -ENODEV;
+
+	ret = platform_driver_register(&tegra194_cpufreq_platform_driver);
+	if (ret)
+		return ret;
+
+	pdev = platform_device_register_simple("tegra194-cpufreq", -1, NULL, 0);
+	if (IS_ERR(pdev)) {
+		platform_driver_unregister(&tegra194_cpufreq_platform_driver);
+		return PTR_ERR(pdev);
+	}
+
+	return 0;
+}
+module_init(tegra_cpufreq_init);
+
+static void __exit tegra_cpufreq_exit(void)
+{
+	platform_driver_unregister(&tegra194_cpufreq_platform_driver);
+}
+module_exit(tegra_cpufreq_exit);
+
+MODULE_AUTHOR("Mikko Perttunen <mperttunen@nvidia.com>");
+MODULE_AUTHOR("Sumit Gupta <sumitg@nvidia.com>");
+MODULE_DESCRIPTION("NVIDIA Tegra194 cpufreq driver");
+MODULE_LICENSE("GPL v2");