Re: [linux-sunxi] [PATCH v6 5/6] drm: sun4i: Add support for enabling DDC I2C bus to sun8i_dw_hdmi glue

[OndÅej Jirman]

Hi Jernej,

On Sun, Jun 16, 2019 at 01:05:13PM +0200, Jernej Åkrabec wrote:
> Hi Ondrej!
> 
> Dne ponedeljek, 27. maj 2019 ob 18:22:36 CEST je megous via linux-sunxi 
> napisal(a):
> > From: Ondrej Jirman <megous@xxxxxxxxxx>
> > 
> > Orange Pi 3 board requires enabling a voltage shifting circuit via GPIO
> > for the DDC bus to be usable.
> > 
> > Add support for hdmi-connector node's optional ddc-en-gpios property to
> > support this use case.
> > 
> > Signed-off-by: Ondrej Jirman <megous@xxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c | 55 +++++++++++++++++++++++++--
> >  drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h |  3 ++
> >  2 files changed, 55 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c
> > b/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c index 39d8509d96a0..59b81ba02d96
> > 100644
> > --- a/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c
> > +++ b/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c
> > @@ -98,6 +98,30 @@ static u32 sun8i_dw_hdmi_find_possible_crtcs(struct
> > drm_device *drm, return crtcs;
> >  }
> > 
> > +static int sun8i_dw_hdmi_find_connector_pdev(struct device *dev,
> > +					     struct 
> platform_device **pdev_out)
> > +{
> > +	struct platform_device *pdev;
> > +	struct device_node *remote;
> > +
> > +	remote = of_graph_get_remote_node(dev->of_node, 1, -1);
> > +	if (!remote)
> > +		return -ENODEV;
> > +
> > +	if (!of_device_is_compatible(remote, "hdmi-connector")) {
> > +		of_node_put(remote);
> > +		return -ENODEV;
> > +	}
> > +
> > +	pdev = of_find_device_by_node(remote);
> > +	of_node_put(remote);
> > +	if (!pdev)
> > +		return -ENODEV;
> > +
> > +	*pdev_out = pdev;
> > +	return 0;
> > +}
> > +
> >  static int sun8i_dw_hdmi_bind(struct device *dev, struct device *master,
> >  			      void *data)
> >  {
> > @@ -151,16 +175,29 @@ static int sun8i_dw_hdmi_bind(struct device *dev,
> > struct device *master, return PTR_ERR(hdmi->regulator);
> >  	}
> > 
> > +	ret = sun8i_dw_hdmi_find_connector_pdev(dev, &hdmi->connector_pdev);
> > +	if (!ret) {
> > +		hdmi->ddc_en = gpiod_get_optional(&hdmi->connector_pdev-
> >dev,
> > +						  "ddc-en", 
> GPIOD_OUT_HIGH);
> > +		if (IS_ERR(hdmi->ddc_en)) {
> > +			platform_device_put(hdmi->connector_pdev);
> > +			dev_err(dev, "Couldn't get ddc-en gpio\n");
> > +			return PTR_ERR(hdmi->ddc_en);
> > +		}
> > +	}
> > +
> >  	ret = regulator_enable(hdmi->regulator);
> >  	if (ret) {
> >  		dev_err(dev, "Failed to enable regulator\n");
> > -		return ret;
> > +		goto err_unref_ddc_en;
> >  	}
> > 
> > +	gpiod_set_value(hdmi->ddc_en, 1);
> 
> Why don't you do that inside if clause where hdmi->ddc_en is assigned? It's 
> not useful otherwise anyway.
> 
> Besides, you would then only need to adjust one goto label in error path.

The idea is to enable DDC after enabling the regulator. I don't think it matters
for the particular HW that's on Orange Pi 3, and similar Xunlong boards, but
this is a fairly generic binding and it makes more sense to power the bus, and
then enable whatever aditional circuitry might be there for the IO.

I can move sun8i_dw_hdmi_find_connector_pdev lower, but I would then need to
disable the regulator in the error path, and I like to keep this order:

- parsing DT
- enabling actual HW stuff

Because parsing is likely to fail with DEFERED_PROBE, because GPIO or whatever
else is not yet ready, and this approach avoids enabling/disabling the HW
needlessly.

> > +
> >  	ret = reset_control_deassert(hdmi->rst_ctrl);
> >  	if (ret) {
> >  		dev_err(dev, "Could not deassert ctrl reset 
> control\n");
> > -		goto err_disable_regulator;
> > +		goto err_disable_ddc_en;
> >  	}
> > 
> >  	ret = clk_prepare_enable(hdmi->clk_tmds);
> > @@ -213,8 +250,14 @@ static int sun8i_dw_hdmi_bind(struct device *dev,
> > struct device *master, clk_disable_unprepare(hdmi->clk_tmds);
> >  err_assert_ctrl_reset:
> >  	reset_control_assert(hdmi->rst_ctrl);
> > -err_disable_regulator:
> > +err_disable_ddc_en:
> > +	gpiod_set_value(hdmi->ddc_en, 0);
> >  	regulator_disable(hdmi->regulator);
> > +err_unref_ddc_en:
> > +	if (hdmi->ddc_en)
> > +		gpiod_put(hdmi->ddc_en);
> > +
> > +	platform_device_put(hdmi->connector_pdev);
> > 
> >  	return ret;
> >  }
> > @@ -228,7 +271,13 @@ static void sun8i_dw_hdmi_unbind(struct device *dev,
> > struct device *master, sun8i_hdmi_phy_remove(hdmi);
> >  	clk_disable_unprepare(hdmi->clk_tmds);
> >  	reset_control_assert(hdmi->rst_ctrl);
> > +	gpiod_set_value(hdmi->ddc_en, 0);
> >  	regulator_disable(hdmi->regulator);
> > +
> > +	if (hdmi->ddc_en)
> > +		gpiod_put(hdmi->ddc_en);
> > +
> > +	platform_device_put(hdmi->connector_pdev);
> >  }
> > 
> >  static const struct component_ops sun8i_dw_hdmi_ops = {
> > diff --git a/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h
> > b/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h index 720c5aa8adc1..dad66b8301c2
> > 100644
> > --- a/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h
> > +++ b/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h
> > @@ -9,6 +9,7 @@
> >  #include <drm/bridge/dw_hdmi.h>
> >  #include <drm/drm_encoder.h>
> >  #include <linux/clk.h>
> > +#include <linux/gpio/consumer.h>
> >  #include <linux/regmap.h>
> >  #include <linux/regulator/consumer.h>
> >  #include <linux/reset.h>
> > @@ -190,6 +191,8 @@ struct sun8i_dw_hdmi {
> >  	struct regulator		*regulator;
> >  	const struct sun8i_dw_hdmi_quirks *quirks;
> >  	struct reset_control		*rst_ctrl;
> > +	struct platform_device		*connector_pdev;
> 
> It seems that connector_pdev is needed only during intialization. Why do you 
> store it?

For some reason I thought that I need to keep it to keep the GPIO available,
but that's not true. I'll drop it.

thank you,
	Ondrej

> Best regards,
> Jernej
> 
> > +	struct gpio_desc		*ddc_en;
> >  };
> > 
> >  static inline struct sun8i_dw_hdmi *