linux-kernel - Re: [PATCH 5/6] media: sun4i: Add H3 deinterlace driver

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Message-ID: <20190912202647.wfcjur7yxhlelvd6@localhost.localdomain>
Date:   Thu, 12 Sep 2019 22:26:47 +0200
From:   Maxime Ripard <mripard@...nel.org>
To:     Jernej Skrabec <jernej.skrabec@...l.net>
Cc:     wens@...e.org, robh+dt@...nel.org, mark.rutland@....com,
        mchehab@...nel.org, hverkuil@...all.nl, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH 5/6] media: sun4i: Add H3 deinterlace driver

Hi,

On Thu, Sep 12, 2019 at 07:51:31PM +0200, Jernej Skrabec wrote:
> +	dev->regmap = devm_regmap_init_mmio(dev->dev, dev->base,
> +					    &deinterlace_regmap_config);
> +	if (IS_ERR(dev->regmap)) {
> +		dev_err(dev->dev, "Couldn't create deinterlace regmap\n");
> +
> +		return PTR_ERR(dev->regmap);
> +	}
> +
> +	ret = clk_prepare_enable(dev->bus_clk);
> +	if (ret) {
> +		dev_err(dev->dev, "Failed to enable bus clock\n");
> +
> +		return ret;
> +	}

Do you need to keep the bus clock enabled all the time? Usually, for
the SoCs that have a reset line, you only need it to read / write to
the registers, not to have the controller actually running.

If you don't, then regmap_init_mmio_clk will take care of that for
you.

> +	clk_set_rate(dev->mod_clk, 300000000);
> +
> +	ret = clk_prepare_enable(dev->mod_clk);
> +	if (ret) {
> +		dev_err(dev->dev, "Failed to enable mod clock\n");
> +
> +		goto err_bus_clk;
> +	}
> +
> +	ret = clk_prepare_enable(dev->ram_clk);
> +	if (ret) {
> +		dev_err(dev->dev, "Failed to enable ram clock\n");
> +
> +		goto err_mod_clk;
> +	}
> +
> +	ret = reset_control_reset(dev->rstc);
> +	if (ret) {
> +		dev_err(dev->dev, "Failed to apply reset\n");
> +
> +		goto err_ram_clk;
> +	}

This could be moved to a runtime_pm hook, with get_sync called in the
open. That way you won't leave the device powered on if it's unused.

> +struct deinterlace_dev {
> +	struct v4l2_device	v4l2_dev;
> +	struct video_device	vfd;
> +	struct device		*dev;
> +	struct v4l2_m2m_dev	*m2m_dev;
> +
> +	/* Device file mutex */
> +	struct mutex		dev_mutex;
> +
> +	void __iomem		*base;
> +	struct regmap		*regmap;

Do you need to store the base address in that structure if you're
using the regmap?

Maxime