media: allegro: add pm_runtime support

The allegro driver must ensure that the mcu and core clocks are enabled
and set to the expected clock rate before trying to load the firmware
and to reset the MCU.

Up until now, the driver assumed that the clocks are always enabled in
the PL (programming logic), because the xlnx_vcu driver did not export
the clocks to other drivers. This has changed and by explicitly enabling
the clocks in the driver, this assumption can be dropped.

It might even be possible to disable the clocks for the encoder if the
encoder is not used. However, the behavior is not documented and it
might be necessary to reinitialize the encoder after deactivating the
clocks. Play it safe by sticking to the current behavior.

Signed-off-by: Michael Tretter <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/platform/allegro-dvt/allegro-core.c

···
  */
 
 #include <linux/bits.h>
+#include <linux/clk.h>
 #include <linux/firmware.h>
 #include <linux/gcd.h>
 #include <linux/interrupt.h>
···
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <linux/sizes.h>
 #include <linux/slab.h>
···
 	struct regmap *regmap;
 	struct regmap *sram;
 	struct regmap *settings;
+
+	struct clk *clk_core;
+	struct clk *clk_mcu;
 
 	const struct fw_info *fw_info;
 	struct allegro_buffer firmware;
···
 	v4l2_info(&dev->v4l2_dev,
 		  "using mcu firmware version '%s'\n", dev->fw_info->version);
 
+	pm_runtime_enable(&dev->plat_dev->dev);
+	err = pm_runtime_resume_and_get(&dev->plat_dev->dev);
+	if (err)
+		goto err_release_firmware_codec;
+
 	/* Ensure that the mcu is sleeping at the reset vector */
 	err = allegro_mcu_reset(dev);
 	if (err) {
 		v4l2_err(&dev->v4l2_dev, "failed to reset mcu\n");
-		goto err_release_firmware_codec;
+		goto err_suspend;
 	}
 
 	allegro_copy_firmware(dev, fw->data, fw->size);
···
 	allegro_mcu_hw_deinit(dev);
 err_free_fw_codec:
 	allegro_free_fw_codec(dev);
+err_suspend:
+	pm_runtime_put(&dev->plat_dev->dev);
+	pm_runtime_disable(&dev->plat_dev->dev);
 err_release_firmware_codec:
 	release_firmware(fw_codec);
 err_release_firmware:
···
 	if (IS_ERR(dev->settings))
 		dev_warn(&pdev->dev, "failed to open settings\n");
 
+	dev->clk_core = devm_clk_get(&pdev->dev, "core_clk");
+	if (IS_ERR(dev->clk_core))
+		return PTR_ERR(dev->clk_core);
+
+	dev->clk_mcu = devm_clk_get(&pdev->dev, "mcu_clk");
+	if (IS_ERR(dev->clk_mcu))
+		return PTR_ERR(dev->clk_mcu);
+
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0)
 		return irq;
···
 		allegro_free_fw_codec(dev);
 	}
 
+	pm_runtime_put(&dev->plat_dev->dev);
+	pm_runtime_disable(&dev->plat_dev->dev);
+
 	v4l2_device_unregister(&dev->v4l2_dev);
+
+	return 0;
+}
+
+static int allegro_runtime_resume(struct device *device)
+{
+	struct allegro_dev *dev = dev_get_drvdata(device);
+	struct regmap *settings = dev->settings;
+	unsigned int clk_mcu;
+	unsigned int clk_core;
+	int err;
+
+	if (!settings)
+		return -EINVAL;
+
+#define MHZ_TO_HZ(freq) ((freq) * 1000 * 1000)
+
+	err = regmap_read(settings, VCU_CORE_CLK, &clk_core);
+	if (err < 0)
+		return err;
+	err = clk_set_rate(dev->clk_core, MHZ_TO_HZ(clk_core));
+	if (err < 0)
+		return err;
+	err = clk_prepare_enable(dev->clk_core);
+	if (err)
+		return err;
+
+	err = regmap_read(settings, VCU_MCU_CLK, &clk_mcu);
+	if (err < 0)
+		goto disable_clk_core;
+	err = clk_set_rate(dev->clk_mcu, MHZ_TO_HZ(clk_mcu));
+	if (err < 0)
+		goto disable_clk_core;
+	err = clk_prepare_enable(dev->clk_mcu);
+	if (err)
+		goto disable_clk_core;
+
+#undef MHZ_TO_HZ
+
+	return 0;
+
+disable_clk_core:
+	clk_disable_unprepare(dev->clk_core);
+
+	return err;
+}
+
+static int allegro_runtime_suspend(struct device *device)
+{
+	struct allegro_dev *dev = dev_get_drvdata(device);
+
+	clk_disable_unprepare(dev->clk_mcu);
+	clk_disable_unprepare(dev->clk_core);
 
 	return 0;
 }
···
 
 MODULE_DEVICE_TABLE(of, allegro_dt_ids);
 
+static const struct dev_pm_ops allegro_pm_ops = {
+	.runtime_resume = allegro_runtime_resume,
+	.runtime_suspend = allegro_runtime_suspend,
+};
+
 static struct platform_driver allegro_driver = {
 	.probe = allegro_probe,
 	.remove = allegro_remove,
 	.driver = {
 		.name = "allegro",
 		.of_match_table = of_match_ptr(allegro_dt_ids),
+		.pm = &allegro_pm_ops,
 	},
 };