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Subject[PATCH] media: stm32-dcmi: Set minimum cpufreq requirement
Date
Before start streaming set cpufreq minimum frequency requirement.
The cpufreq governor will adapt the frequencies and we will have
no latency for handling interrupts.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
---
drivers/media/platform/stm32/stm32-dcmi.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c
index b8931490b83b..97c342351569 100644
--- a/drivers/media/platform/stm32/stm32-dcmi.c
+++ b/drivers/media/platform/stm32/stm32-dcmi.c
@@ -13,6 +13,7 @@

#include <linux/clk.h>
#include <linux/completion.h>
+#include <linux/cpufreq.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/init.h>
@@ -99,6 +100,8 @@ enum state {

#define OVERRUN_ERROR_THRESHOLD 3

+#define DCMI_MIN_FREQ 650000 /* in KHz */
+
struct dcmi_graph_entity {
struct v4l2_async_subdev asd;

@@ -173,6 +176,10 @@ struct stm32_dcmi {
struct media_device mdev;
struct media_pad vid_cap_pad;
struct media_pipeline pipeline;
+
+ /* CPU freq contraint */
+ struct cpufreq_policy *policy;
+ struct freq_qos_request qos_req;
};

static inline struct stm32_dcmi *notifier_to_dcmi(struct v4l2_async_notifier *n)
@@ -736,11 +743,20 @@ static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
goto err_release_buffers;
}

+ if (dcmi->policy) {
+ ret = freq_qos_add_request(&dcmi->policy->constraints,
+ &dcmi->qos_req, FREQ_QOS_MIN,
+ DCMI_MIN_FREQ);
+
+ if (ret < 0)
+ goto err_pm_put;
+ }
+
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);
@@ -835,6 +851,9 @@ static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
err_media_pipeline_stop:
media_pipeline_stop(&dcmi->vdev->entity);

+err_drop_qos:
+ if (dcmi->policy)
+ freq_qos_remove_request(&dcmi->qos_req);
err_pm_put:
pm_runtime_put(dcmi->dev);

@@ -863,6 +882,9 @@ static void dcmi_stop_streaming(struct vb2_queue *vq)

media_pipeline_stop(&dcmi->vdev->entity);

+ if (dcmi->policy)
+ freq_qos_remove_request(&dcmi->qos_req);
+
spin_lock_irq(&dcmi->irqlock);

/* Disable interruptions */
@@ -2020,6 +2042,8 @@ static int dcmi_probe(struct platform_device *pdev)
goto err_cleanup;
}

+ dcmi->policy = cpufreq_cpu_get(0);
+
dev_info(&pdev->dev, "Probe done\n");

platform_set_drvdata(pdev, dcmi);
@@ -2049,6 +2073,9 @@ static int dcmi_remove(struct platform_device *pdev)

pm_runtime_disable(&pdev->dev);

+ if (dcmi->policy)
+ cpufreq_cpu_put(dcmi->policy);
+
v4l2_async_notifier_unregister(&dcmi->notifier);
v4l2_async_notifier_cleanup(&dcmi->notifier);
media_entity_cleanup(&dcmi->vdev->entity);
--
2.15.0
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