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

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Date:   Sun, 29 Sep 2019 15:18:58 +0200
From:   Jernej Škrabec <jernej.skrabec@...l.net>
To:     Maxime Ripard <mripard@...nel.org>
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

Dne četrtek, 12. september 2019 ob 22:26:47 CEST je Maxime Ripard napisal(a):
> 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.

I just tested and using regmap_init_mmio_clk() with "bus" clock doesn't work. 
I guess it has to be enabled whole time. I'll just leave it as-is.

Best regards,
Jernej

> 
> > +	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