[PATCH v3 0/3] DCMI set minimum cpufreq requirement

[PATCH v3 0/3] DCMI set minimum cpufreq requirement

[Benjamin Gaignard]

This series allow to STM32 camera interface (DCMI) to require a minimum
frequency to the CPUs before start streaming frames from the sensor.
The minimum frequency requirement is provided in the devide-tree node.

Setting a minimum frequency for the CPUs is needed to ensure a quick handling
of the interrupts between two sensor frames and avoid dropping half of them.

version 3:
- add a cpumask field to track boosted CPUs
- add irq_affinity_notify callback
- protect cpumask field with a mutex 

Benjamin Gaignard (3):
  dt-bindings: media: stm32-dcmi: Add DCMI min frequency property
  media: stm32-dcmi: Set minimum cpufreq requirement
  ARM: dts: stm32: Set DCMI frequency requirement for stm32mp15x

 .../devicetree/bindings/media/st,stm32-dcmi.yaml   |   8 +
 arch/arm/boot/dts/stm32mp151.dtsi                  |   1 +
 drivers/media/platform/stm32/stm32-dcmi.c          | 187 ++++++++++++++++++++-
 3 files changed, 188 insertions(+), 8 deletions(-)

-- 
2.15.0

[PATCH v3 1/3] dt-bindings: media: stm32-dcmi: Add DCMI min frequency property

[Benjamin Gaignard]

Document st,stm32-dcmi-min-frequency property which is used to
request CPUs minimum frequency when streaming frames.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
---
 Documentation/devicetree/bindings/media/st,stm32-dcmi.yaml | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/devicetree/bindings/media/st,stm32-dcmi.yaml b/Documentation/devicetree/bindings/media/st,stm32-dcmi.yaml
index 3fe778cb5cc3..05ca85a2411a 100644
--- a/Documentation/devicetree/bindings/media/st,stm32-dcmi.yaml
+++ b/Documentation/devicetree/bindings/media/st,stm32-dcmi.yaml
@@ -44,6 +44,13 @@ properties:
       bindings defined in
       Documentation/devicetree/bindings/media/video-interfaces.txt.
 
+  st,stm32-dcmi-min-frequency:
+    description: DCMI minimum CPUs frequency requirement (in KHz).
+    allOf:
+      - $ref: /schemas/types.yaml#/definitions/uint32
+      - minimum: 0
+      - default: 0
+
 required:
   - compatible
   - reg
@@ -71,6 +78,7 @@ examples:
         clock-names = "mclk";
         dmas = <&dmamux1 75 0x400 0x0d>;
         dma-names = "tx";
+        st,stm32-dcmi-min-frequency = <650000>;
 
         port {
              dcmi_0: endpoint {
-- 
2.15.0

[PATCH v3 2/3] media: stm32-dcmi: Set minimum cpufreq requirement

[Benjamin Gaignard]

Before start streaming set cpufreq minimum frequency requirement.
The cpufreq governor will adapt the frequencies and we will have
no latency for handling interrupts.
The frequency requirement is retrieved from the device-tree node.

While streaming be notified if the IRQ affinity change thanks to 
irq_affinity_notify callback.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
---
version 3:
- add a cpumask field to track boosted CPUs
- add irq_affinity_notify callback
- protect cpumask field with a mutex 

 drivers/media/platform/stm32/stm32-dcmi.c | 187 ++++++++++++++++++++++++++++--
 1 file changed, 179 insertions(+), 8 deletions(-)

diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c
index b8931490b83b..fb6ab09eaff0 100644
--- a/drivers/media/platform/stm32/stm32-dcmi.c
+++ b/drivers/media/platform/stm32/stm32-dcmi.c
@@ -13,10 +13,13 @@
 
 #include <linux/clk.h>
 #include <linux/completion.h>
+#include <linux/cpufreq.h>
+#include <linux/cpumask.h>
 #include <linux/delay.h>
 #include <linux/dmaengine.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
+#include <linux/irq.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -99,6 +102,8 @@ enum state {
 
 #define OVERRUN_ERROR_THRESHOLD	3
 
+static DEFINE_PER_CPU(struct freq_qos_request, qos_req);
+
 struct dcmi_graph_entity {
 	struct v4l2_async_subdev asd;
 
@@ -133,6 +138,7 @@ struct stm32_dcmi {
 	struct resource			*res;
 	struct reset_control		*rstc;
 	int				sequence;
+	int				irq;
 	struct list_head		buffers;
 	struct dcmi_buf			*active;
 
@@ -173,6 +179,11 @@ struct stm32_dcmi {
 	struct media_device		mdev;
 	struct media_pad		vid_cap_pad;
 	struct media_pipeline		pipeline;
+
+	u32				min_frequency;
+	cpumask_var_t			boosted;
+	struct irq_affinity_notify	notify;
+	struct mutex			freq_lock;
 };
 
 static inline struct stm32_dcmi *notifier_to_dcmi(struct v4l2_async_notifier *n)
@@ -722,6 +733,156 @@ static void dcmi_pipeline_stop(struct stm32_dcmi *dcmi)
 	dcmi_pipeline_s_stream(dcmi, 0);
 }
 
+static void dcmi_get_min_frequency(struct stm32_dcmi *dcmi)
+{
+	struct device_node *np = dcmi->mdev.dev->of_node;
+
+	dcmi->min_frequency = FREQ_QOS_MIN_DEFAULT_VALUE;
+
+	of_property_read_u32(np, "st,stm32-dcmi-min-frequency",
+			     &dcmi->min_frequency);
+}
+
+static void dcmi_irq_notifier_notify(struct irq_affinity_notify *notify,
+				     const cpumask_t *mask)
+{
+	struct stm32_dcmi *dcmi = container_of(notify,
+					       struct stm32_dcmi,
+					       notify);
+	struct cpufreq_policy *p;
+	int cpu;
+
+	mutex_lock(&dcmi->freq_lock);
+	/*
+	 * For all boosted CPUs check if it is still the case
+	 * if not remove the request
+	 */
+	for_each_cpu(cpu, dcmi->boosted) {
+		if (cpumask_test_cpu(cpu, mask))
+			continue;
+
+		p = cpufreq_cpu_get(cpu);
+		if (!p)
+			continue;
+
+		freq_qos_remove_request(&per_cpu(qos_req, cpu));
+		cpumask_andnot(dcmi->boosted, dcmi->boosted, p->cpus);
+
+		cpufreq_cpu_put(p);
+	}
+
+	/*
+	 * For CPUs in the mask check if they are boosted if not add
+	 * a request
+	 */
+	for_each_cpu(cpu, mask) {
+		if (cpumask_test_cpu(cpu, dcmi->boosted))
+			continue;
+
+		p = cpufreq_cpu_get(cpu);
+		if (!p)
+			continue;
+
+		freq_qos_add_request(&p->constraints, &per_cpu(qos_req, cpu),
+				     FREQ_QOS_MIN, dcmi->min_frequency);
+		cpumask_or(dcmi->boosted, dcmi->boosted, p->cpus);
+		cpufreq_cpu_put(p);
+	}
+
+	mutex_unlock(&dcmi->freq_lock);
+}
+
+static void dcmi_irq_notifier_release(struct kref *ref)
+{
+	/*
+	 * This is required by affinity notifier. We don't have anything to
+	 * free here.
+	 */
+}
+
+static void dcmi_get_cpu_policy(struct stm32_dcmi *dcmi)
+{
+	struct cpufreq_policy *p;
+	int cpu;
+
+	if (!alloc_cpumask_var(&dcmi->boosted, GFP_KERNEL))
+		return;
+
+	mutex_lock(&dcmi->freq_lock);
+
+	for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) {
+		if (cpumask_test_cpu(cpu, dcmi->boosted))
+			continue;
+
+		p = cpufreq_cpu_get(cpu);
+		if (!p)
+			continue;
+
+		freq_qos_add_request(&p->constraints, &per_cpu(qos_req, cpu),
+				     FREQ_QOS_MIN, FREQ_QOS_MIN_DEFAULT_VALUE);
+
+		cpumask_or(dcmi->boosted, dcmi->boosted, p->cpus);
+
+		cpufreq_cpu_put(p);
+	}
+
+	mutex_unlock(&dcmi->freq_lock);
+}
+
+static void dcmi_put_cpu_policy(struct stm32_dcmi *dcmi)
+{
+	struct cpufreq_policy *p;
+	int cpu;
+
+	mutex_lock(&dcmi->freq_lock);
+
+	for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) {
+		if (!cpumask_test_cpu(cpu, dcmi->boosted))
+			continue;
+
+		p = cpufreq_cpu_get(cpu);
+		if (!p)
+			continue;
+
+		freq_qos_remove_request(&per_cpu(qos_req, cpu));
+		cpumask_andnot(dcmi->boosted, dcmi->boosted, p->cpus);
+
+		cpufreq_cpu_put(p);
+	}
+
+	free_cpumask_var(dcmi->boosted);
+
+	mutex_unlock(&dcmi->freq_lock);
+}
+
+static void dcmi_set_min_frequency(struct stm32_dcmi *dcmi, s32 freq)
+{
+	struct irq_affinity_notify *notify = &dcmi->notify;
+	int cpu;
+
+	mutex_lock(&dcmi->freq_lock);
+
+	for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) {
+		if (!cpumask_test_cpu(cpu, dcmi->boosted))
+			continue;
+
+		if (!freq_qos_request_active(&per_cpu(qos_req, cpu)))
+			continue;
+
+		freq_qos_update_request(&per_cpu(qos_req, cpu), freq);
+	}
+
+	mutex_unlock(&dcmi->freq_lock);
+
+	if (freq != FREQ_QOS_MIN_DEFAULT_VALUE) {
+		notify->notify = dcmi_irq_notifier_notify;
+		notify->release = dcmi_irq_notifier_release;
+		irq_set_affinity_notifier(dcmi->irq, notify);
+	} else {
+		irq_set_affinity_notifier(dcmi->irq, NULL);
+	}
+}
+
 static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
 {
 	struct stm32_dcmi *dcmi = vb2_get_drv_priv(vq);
@@ -736,11 +897,13 @@ static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
 		goto err_release_buffers;
 	}
 
+	dcmi_set_min_frequency(dcmi, dcmi->min_frequency);
+
 	ret = media_pipeline_start(&dcmi->vdev->entity, &dcmi->pipeline);
 	if (ret < 0) {
 		dev_err(dcmi->dev, "%s: Failed to start streaming, media pipeline start error (%d)\n",
 			__func__, ret);
-		goto err_pm_put;
+		goto err_drop_qos;
 	}
 
 	ret = dcmi_pipeline_start(dcmi);
@@ -835,7 +998,8 @@ static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
 err_media_pipeline_stop:
 	media_pipeline_stop(&dcmi->vdev->entity);
 
-err_pm_put:
+err_drop_qos:
+	dcmi_set_min_frequency(dcmi, FREQ_QOS_MIN_DEFAULT_VALUE);
 	pm_runtime_put(dcmi->dev);
 
 err_release_buffers:
@@ -863,6 +1027,8 @@ static void dcmi_stop_streaming(struct vb2_queue *vq)
 
 	media_pipeline_stop(&dcmi->vdev->entity);
 
+	dcmi_set_min_frequency(dcmi, FREQ_QOS_MIN_DEFAULT_VALUE);
+
 	spin_lock_irq(&dcmi->irqlock);
 
 	/* Disable interruptions */
@@ -1838,7 +2004,6 @@ static int dcmi_probe(struct platform_device *pdev)
 	struct vb2_queue *q;
 	struct dma_chan *chan;
 	struct clk *mclk;
-	int irq;
 	int ret = 0;
 
 	match = of_match_device(of_match_ptr(stm32_dcmi_of_match), &pdev->dev);
@@ -1879,9 +2044,9 @@ static int dcmi_probe(struct platform_device *pdev)
 	dcmi->bus.bus_width = ep.bus.parallel.bus_width;
 	dcmi->bus.data_shift = ep.bus.parallel.data_shift;
 
-	irq = platform_get_irq(pdev, 0);
-	if (irq <= 0)
-		return irq ? irq : -ENXIO;
+	dcmi->irq = platform_get_irq(pdev, 0);
+	if (dcmi->irq <= 0)
+		return dcmi->irq ? dcmi->irq : -ENXIO;
 
 	dcmi->res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!dcmi->res) {
@@ -1895,11 +2060,12 @@ static int dcmi_probe(struct platform_device *pdev)
 		return PTR_ERR(dcmi->regs);
 	}
 
-	ret = devm_request_threaded_irq(&pdev->dev, irq, dcmi_irq_callback,
+	ret = devm_request_threaded_irq(&pdev->dev, dcmi->irq,
+					dcmi_irq_callback,
 					dcmi_irq_thread, IRQF_ONESHOT,
 					dev_name(&pdev->dev), dcmi);
 	if (ret) {
-		dev_err(&pdev->dev, "Unable to request irq %d\n", irq);
+		dev_err(&pdev->dev, "Unable to request irq %d\n", dcmi->irq);
 		return ret;
 	}
 
@@ -2022,6 +2188,9 @@ static int dcmi_probe(struct platform_device *pdev)
 
 	dev_info(&pdev->dev, "Probe done\n");
 
+	dcmi_get_min_frequency(dcmi);
+	dcmi_get_cpu_policy(dcmi);
+
 	platform_set_drvdata(pdev, dcmi);
 
 	pm_runtime_enable(&pdev->dev);
@@ -2049,6 +2218,8 @@ static int dcmi_remove(struct platform_device *pdev)
 
 	pm_runtime_disable(&pdev->dev);
 
+	dcmi_put_cpu_policy(dcmi);
+
 	v4l2_async_notifier_unregister(&dcmi->notifier);
 	v4l2_async_notifier_cleanup(&dcmi->notifier);
 	media_entity_cleanup(&dcmi->vdev->entity);
-- 
2.15.0

[PATCH v3 3/3] ARM: dts: stm32: Set DCMI frequency requirement for stm32mp15x

[Benjamin Gaignard]

Make sure that CPUs will at least run at 650Mhz when streaming
sensor frames.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
---
 arch/arm/boot/dts/stm32mp151.dtsi | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/boot/dts/stm32mp151.dtsi b/arch/arm/boot/dts/stm32mp151.dtsi
index 3ea05ba48215..f6d7bf4f8231 100644
--- a/arch/arm/boot/dts/stm32mp151.dtsi
+++ b/arch/arm/boot/dts/stm32mp151.dtsi
@@ -1091,6 +1091,7 @@
 			clock-names = "mclk";
 			dmas = <&dmamux1 75 0x400 0x0d>;
 			dma-names = "tx";
+			st,stm32-dcmi-min-frequency = <650000>;
 			status = "disabled";
 		};
 
-- 
2.15.0

Re: [PATCH v3 2/3] media: stm32-dcmi: Set minimum cpufreq requirement

[Valentin Schneider]

On 04/06/20 13:39, Benjamin Gaignard wrote:
> Before start streaming set cpufreq minimum frequency requirement.
> The cpufreq governor will adapt the frequencies and we will have
> no latency for handling interrupts.
> The frequency requirement is retrieved from the device-tree node.
>
> While streaming be notified if the IRQ affinity change thanks to
> irq_affinity_notify callback.
>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
> ---
> version 3:
> - add a cpumask field to track boosted CPUs
> - add irq_affinity_notify callback
> - protect cpumask field with a mutex
>
>  drivers/media/platform/stm32/stm32-dcmi.c | 187 ++++++++++++++++++++++++++++--
>  1 file changed, 179 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c
> index b8931490b83b..fb6ab09eaff0 100644
> --- a/drivers/media/platform/stm32/stm32-dcmi.c
> +++ b/drivers/media/platform/stm32/stm32-dcmi.c
> +static void dcmi_irq_notifier_notify(struct irq_affinity_notify *notify,
> +				     const cpumask_t *mask)
> +{
> +	struct stm32_dcmi *dcmi = container_of(notify,
> +					       struct stm32_dcmi,
> +					       notify);
> +	struct cpufreq_policy *p;
> +	int cpu;
> +
> +	mutex_lock(&dcmi->freq_lock);
> +	/*
> +	 * For all boosted CPUs check if it is still the case
> +	 * if not remove the request
> +	 */
> +	for_each_cpu(cpu, dcmi->boosted) {
> +		if (cpumask_test_cpu(cpu, mask))
> +			continue;
> +
> +		p = cpufreq_cpu_get(cpu);
> +		if (!p)
> +			continue;
> +
> +		freq_qos_remove_request(&per_cpu(qos_req, cpu));
> +		cpumask_andnot(dcmi->boosted, dcmi->boosted, p->cpus);
> +
> +		cpufreq_cpu_put(p);
> +	}
> +
> +	/*
> +	 * For CPUs in the mask check if they are boosted if not add
> +	 * a request
> +	 */
> +	for_each_cpu(cpu, mask) {
> +		if (cpumask_test_cpu(cpu, dcmi->boosted))
> +			continue;
> +
> +		p = cpufreq_cpu_get(cpu);
> +		if (!p)
> +			continue;
> +
> +		freq_qos_add_request(&p->constraints, &per_cpu(qos_req, cpu),
> +				     FREQ_QOS_MIN, dcmi->min_frequency);
> +		cpumask_or(dcmi->boosted, dcmi->boosted, p->cpus);
> +		cpufreq_cpu_put(p);
> +	}
> +
> +	mutex_unlock(&dcmi->freq_lock);

That looks about right.

> +}
> +
> +static void dcmi_irq_notifier_release(struct kref *ref)
> +{
> +	/*
> +	 * This is required by affinity notifier. We don't have anything to
> +	 * free here.
> +	 */
> +}
> +
> +static void dcmi_get_cpu_policy(struct stm32_dcmi *dcmi)
> +{
> +	struct cpufreq_policy *p;
> +	int cpu;
> +
> +	if (!alloc_cpumask_var(&dcmi->boosted, GFP_KERNEL))
> +		return;

I think you want to actually return i.e. -ENOMEM and do cleanups in the
probe; otherwise you'll silently continue.

> +
> +	mutex_lock(&dcmi->freq_lock);
> +
> +	for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) {

When I suggested serialization, I was thinking we may want to use the irq's
desc lock to prevent the affinity from moving under our feet. Something
like:

  CPU A                                          CPU B

  for_each_cpu(cpu, mask)
    cpu = cpumask_next(cpu, mask)

    // ...                                       cpumask_copy(desc->irq_common_data.affinity, mask)

    cpu = cpumask_next(cpu, mask)

Now, should that happen, we would still queue the notifier and run it
shortly after - and since you track which CPUs are boosted, I don't think
we have any loss of information here.

We may have yet another affinity change while the notifier is still queued;
but the notifier boilerplate does grab the desc lock, so I think it's all
good - it wasn't all super obvious so I figured I'd still point it out.

> +		if (cpumask_test_cpu(cpu, dcmi->boosted))
> +			continue;
> +
> +		p = cpufreq_cpu_get(cpu);
> +		if (!p)
> +			continue;
> +
> +		freq_qos_add_request(&p->constraints, &per_cpu(qos_req, cpu),
> +				     FREQ_QOS_MIN, FREQ_QOS_MIN_DEFAULT_VALUE);
> +
> +		cpumask_or(dcmi->boosted, dcmi->boosted, p->cpus);
> +
> +		cpufreq_cpu_put(p);
> +	}
> +
> +	mutex_unlock(&dcmi->freq_lock);
> +}
> +
> +static void dcmi_put_cpu_policy(struct stm32_dcmi *dcmi)
> +{
> +	struct cpufreq_policy *p;
> +	int cpu;
> +
> +	mutex_lock(&dcmi->freq_lock);
> +
> +	for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) {
> +		if (!cpumask_test_cpu(cpu, dcmi->boosted))
> +			continue;
> +
> +		p = cpufreq_cpu_get(cpu);
> +		if (!p)
> +			continue;
> +
> +		freq_qos_remove_request(&per_cpu(qos_req, cpu));
> +		cpumask_andnot(dcmi->boosted, dcmi->boosted, p->cpus);
> +
> +		cpufreq_cpu_put(p);
> +	}
> +
> +	free_cpumask_var(dcmi->boosted);
> +
> +	mutex_unlock(&dcmi->freq_lock);
> +}
> +
> +static void dcmi_set_min_frequency(struct stm32_dcmi *dcmi, s32 freq)
> +{
> +	struct irq_affinity_notify *notify = &dcmi->notify;
> +	int cpu;
> +
> +	mutex_lock(&dcmi->freq_lock);
> +
> +	for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) {
> +		if (!cpumask_test_cpu(cpu, dcmi->boosted))
> +			continue;
> +

If the affinity changed between say .probe() and .start_streaming(), IIUC
you may skip CPUs here - and even if you initialize the notifier earlier in
the function (see below), that won't help you.

I think dcmi_irq_notifier_notify() does almost all you want, if it also did
the QoS update for CPUs that weren't affected by the affinity change, you
may be able to just do:

   dcmi_irq_notifier_notify(irq_get_affinity_mask(dcmi->irq));

Or something along those lines.

> +		if (!freq_qos_request_active(&per_cpu(qos_req, cpu)))
> +			continue;
> +
> +		freq_qos_update_request(&per_cpu(qos_req, cpu), freq);
> +	}
> +
> +	mutex_unlock(&dcmi->freq_lock);
> +
> +	if (freq != FREQ_QOS_MIN_DEFAULT_VALUE) {