Message-ID: <20180314100902.GB16424@w540>
Date:   Wed, 14 Mar 2018 11:09:02 +0100
From:   jacopo mondi <jacopo@...ndi.org>
To:     Andrzej Hajda <a.hajda@...sung.com>
Cc:     Jacopo Mondi <jacopo+renesas@...ndi.org>, architt@...eaurora.org,
        Laurent.pinchart@...asonboard.com, airlied@...ux.ie,
        horms@...ge.net.au, magnus.damm@...il.com, geert@...ux-m68k.org,
        niklas.soderlund@...natech.se, sergei.shtylyov@...entembedded.com,
        robh+dt@...nel.org, mark.rutland@....com,
        dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] drm: bridge: Add thc63lvd1024 LVDS decoder driver

Hi Andrzej,
    thanks for review

On Wed, Mar 14, 2018 at 09:42:36AM +0100, Andrzej Hajda wrote:
> On 13.03.2018 15:30, Jacopo Mondi wrote:
> > Add DRM bridge driver for Thine THC63LVD1024 LVDS to digital parallel
> > output decoder.
>
> IMO converter suits here better, but it is just suggestion.
>
> >
> > Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> > ---
> >  drivers/gpu/drm/bridge/Kconfig        |   7 +
> >  drivers/gpu/drm/bridge/Makefile       |   1 +
> >  drivers/gpu/drm/bridge/thc63lvd1024.c | 241 ++++++++++++++++++++++++++++++++++
> >  3 files changed, 249 insertions(+)
> >  create mode 100644 drivers/gpu/drm/bridge/thc63lvd1024.c
> >
> > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> > index 3b99d5a..facf6bd 100644
> > --- a/drivers/gpu/drm/bridge/Kconfig
> > +++ b/drivers/gpu/drm/bridge/Kconfig
> > @@ -92,6 +92,13 @@ config DRM_SII9234
> >  	  It is an I2C driver, that detects connection of MHL bridge
> >  	  and starts encapsulation of HDMI signal.
> >
> > +config DRM_THINE_THC63LVD1024
> > +	tristate "Thine THC63LVD1024 LVDS decoder bridge"
> > +	depends on OF
> > +	select DRM_PANEL_BRIDGE
>
> You don't use PANEL_BRIDGE, it should be possible to drop the select.
>

Ack

> > +	---help---
> > +	  Thine THC63LVD1024 LVDS decoder bridge driver.
>
> Decoder to what?
> Maybe it would be better to say it is LVDS/parallel or LVDS/RGB
> converter or bridge.

"LVDS to digital CMOS/TTL parallel data converter" as the manual
describes the chip?

>
> > +
> >  config DRM_TOSHIBA_TC358767
> >  	tristate "Toshiba TC358767 eDP bridge"
> >  	depends on OF
> > diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> > index 373eb28..fd90b16 100644
> > --- a/drivers/gpu/drm/bridge/Makefile
> > +++ b/drivers/gpu/drm/bridge/Makefile
> > @@ -8,6 +8,7 @@ obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
> >  obj-$(CONFIG_DRM_SIL_SII8620) += sil-sii8620.o
> >  obj-$(CONFIG_DRM_SII902X) += sii902x.o
> >  obj-$(CONFIG_DRM_SII9234) += sii9234.o
> > +obj-$(CONFIG_DRM_THINE_THC63LVD1024) += thc63lvd1024.o
> >  obj-$(CONFIG_DRM_TOSHIBA_TC358767) += tc358767.o
> >  obj-$(CONFIG_DRM_ANALOGIX_DP) += analogix/
> >  obj-$(CONFIG_DRM_I2C_ADV7511) += adv7511/
> > diff --git a/drivers/gpu/drm/bridge/thc63lvd1024.c b/drivers/gpu/drm/bridge/thc63lvd1024.c
> > new file mode 100644
> > index 0000000..4b059c0
> > --- /dev/null
> > +++ b/drivers/gpu/drm/bridge/thc63lvd1024.c
> > @@ -0,0 +1,241 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * THC63LVD1024 LVDS to parallel data DRM bridge driver.
> > + *
> > + * Copyright (C) 2018 Jacopo Mondi <jacopo+renesas@...ndi.org>
> > + */
> > +
> > +#include <drm/drmP.h>
> > +#include <drm/drm_bridge.h>
> > +#include <drm/drm_panel.h>
> > +
> > +#include <linux/gpio/consumer.h>
> > +#include <linux/of_graph.h>
> > +#include <linux/regulator/consumer.h>
> > +
> > +static const char * const thc63_reg_names[] = {
> > +	"vcc", "lvcc", "pvcc", "cvcc", };
> > +
> > +struct thc63_dev {
> > +	struct device *dev;
> > +
> > +	struct regulator *vccs[ARRAY_SIZE(thc63_reg_names)];
> > +
> > +	struct gpio_desc *pwdn;
> > +	struct gpio_desc *oe;
> > +
> > +	struct drm_bridge bridge;
> > +	struct drm_bridge *next;
> > +};
> > +
> > +static inline struct thc63_dev *to_thc63(struct drm_bridge *bridge)
> > +{
> > +	return container_of(bridge, struct thc63_dev, bridge);
> > +}
> > +
> > +static int thc63_attach(struct drm_bridge *bridge)
> > +{
> > +	struct thc63_dev *thc63 = to_thc63(bridge);
> > +
> > +	return drm_bridge_attach(bridge->encoder, thc63->next, bridge);
> > +}
> > +
> > +static void thc63_enable(struct drm_bridge *bridge)
> > +{
> > +	struct thc63_dev *thc63 = to_thc63(bridge);
> > +	struct regulator *vcc;
> > +	unsigned int i;
> > +	int ret;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(thc63->vccs); i++) {
> > +		vcc = thc63->vccs[i];
> > +		if (vcc) {
> > +			ret = regulator_enable(vcc);
> > +			if (ret)
> > +				goto error_vcc_enable;
> > +		}
> > +	}
> > +
> > +	if (thc63->pwdn)
> > +		gpiod_set_value(thc63->pwdn, 0);
> > +
> > +	if (thc63->oe)
> > +		gpiod_set_value(thc63->oe, 1);
> > +
> > +	return;
> > +
> > +error_vcc_enable:
> > +	dev_err(thc63->dev, "Failed to enable regulator %u\n", i);
> > +}
> > +
> > +static void thc63_disable(struct drm_bridge *bridge)
> > +{
> > +	struct thc63_dev *thc63 = to_thc63(bridge);
> > +	struct regulator *vcc;
> > +	unsigned int i;
> > +	int ret;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(thc63->vccs); i++) {
> > +		vcc = thc63->vccs[i];
> > +		if (vcc) {
> > +			ret = regulator_disable(vcc);
> > +			if (ret)
> > +				goto error_vcc_disable;
>
> I think in disable path you can report an error and continue - should be
> safer.
>

Ack

> > +		}
> > +	}
> > +
> > +	if (thc63->pwdn)
> > +		gpiod_set_value(thc63->pwdn, 1);
> > +
> > +	if (thc63->oe)
> > +		gpiod_set_value(thc63->oe, 0);
>
> Usually disable uses reverse order. Ie first disable oe, then, pwdn,
> then regulators, also in reverse order.
> Looks more reasonable.
>

Indeed! I will invert the order.

(I wonder if the regulator disabling order actually makes a difference
though).

> > +
> > +	return;
> > +
> > +error_vcc_disable:
> > +	dev_err(thc63->dev, "Failed to disable regulator %u\n", i);
> > +}
> > +
> > +struct drm_bridge_funcs thc63_bridge_func = {
> > +	.attach	= thc63_attach,
> > +	.enable = thc63_enable,
> > +	.disable = thc63_disable,
> > +};
> > +
> > +static int thc63_parse_dt(struct thc63_dev *thc63)
> > +{
> > +	struct device_node *thc63_out;
> > +	struct device_node *remote;
> > +	int ret = 0;
> > +
> > +	thc63_out = of_graph_get_endpoint_by_regs(thc63->dev->of_node, 2, -1);
>
> Please define and use enums for port number, it will be more clear.
>

yup

> > +	if (!thc63_out) {
> > +		dev_err(thc63->dev, "Missing endpoint in Port@2\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	remote = of_graph_get_remote_port_parent(thc63_out);
> > +	if (!remote) {
> > +		dev_err(thc63->dev, "Endpoint in Port@2 unconnected\n");
> > +		ret = -ENODEV;
> > +		goto error_put_out_node;
> > +	}
> > +
> > +	if (!of_device_is_available(remote)) {
> > +		dev_err(thc63->dev, "Port@2 remote endpoint is disabled\n");
> > +		ret = -ENODEV;
> > +		goto error_put_remote_node;
> > +	}
> > +
> > +	thc63->next = of_drm_find_bridge(remote);
> > +	if (!thc63->next)
> > +		ret = -EPROBE_DEFER;
> > +
> > +error_put_remote_node:
> > +	of_node_put(remote);
> > +error_put_out_node:
> > +	of_node_put(thc63_out);
> > +
> > +	return ret;
> > +}
> > +
> > +static int thc63_gpio_init(struct thc63_dev *thc63)
> > +{
> > +	thc63->pwdn = devm_gpiod_get_optional(thc63->dev, "pwdn",
> > +					      GPIOD_OUT_LOW);
> Shouldn't be GPIOD_OUT_HIGH - bridge initially disabled?

No, the PWDN gpio is active low, it puts the chip in power down mode
when the physical line level is set to 0.

That's another confusing thing, when requesting the GPIO, the actual
physical line value has to be provided, while when "set_value()" the
logical one is requested, iirc.

Being the GPIO defined as active low, in power enable we set it to
"logical inactive" == "physical 1", while during power disable it has
to be set to "logical active" == "physical 0"

Not the right place to complain here, but imo that's not consistent.
Or have I misinterpreted the APIs? I cannot do much test, as in my setup
the PWDN pin is hardwired to +vcc (through a physical switch, not
controlled through a GPIO though).

Thanks
   j

>
> Regards
> Andrzej
> > +	if (IS_ERR(thc63->pwdn)) {
> > +		dev_err(thc63->dev, "Unable to get GPIO \"pwdn\"\n");
> > +		return PTR_ERR(thc63->pwdn);
> > +	}
> > +
> > +	thc63->oe = devm_gpiod_get_optional(thc63->dev, "oe", GPIOD_OUT_LOW);
> > +	if (IS_ERR(thc63->oe)) {
> > +		dev_err(thc63->dev, "Unable to get GPIO \"oe\"\n");
> > +		return PTR_ERR(thc63->oe);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int thc63_regulator_init(struct thc63_dev *thc63)
> > +{
> > +	struct regulator **reg;
> > +	int i;
> > +
> > +	reg = &thc63->vccs[0];
> > +	for (i = 0; i < ARRAY_SIZE(thc63->vccs); i++, reg++) {
> > +		*reg = devm_regulator_get_optional(thc63->dev,
> > +						   thc63_reg_names[i]);
> > +		if (IS_ERR(*reg)) {
> > +			if (PTR_ERR(*reg) == -EPROBE_DEFER)
> > +				return -EPROBE_DEFER;
> > +			*reg = NULL;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int thc63_probe(struct platform_device *pdev)
> > +{
> > +	struct thc63_dev *thc63;
> > +	int ret;
> > +
> > +	thc63 = devm_kzalloc(&pdev->dev, sizeof(*thc63), GFP_KERNEL);
> > +	if (!thc63)
> > +		return -ENOMEM;
> > +
> > +	thc63->dev = &pdev->dev;
> > +	platform_set_drvdata(pdev, thc63);
> > +
> > +	ret = thc63_regulator_init(thc63);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = thc63_gpio_init(thc63);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = thc63_parse_dt(thc63);
> > +	if (ret)
> > +		return ret;
> > +
> > +	thc63->bridge.driver_private = thc63;
> > +	thc63->bridge.of_node = pdev->dev.of_node;
> > +	thc63->bridge.funcs = &thc63_bridge_func;
> > +
> > +	drm_bridge_add(&thc63->bridge);
> > +
> > +	return 0;
> > +}
> > +
> > +static int thc63_remove(struct platform_device *pdev)
> > +{
> > +	struct thc63_dev *thc63 = platform_get_drvdata(pdev);
> > +
> > +	drm_bridge_remove(&thc63->bridge);
> > +
> > +	return 0;
> > +}
> > +
> > +#ifdef CONFIG_OF
> > +static const struct of_device_id thc63_match[] = {
> > +	{ .compatible = "thine,thc63lvd1024", },
> > +	{ },
> > +};
> > +MODULE_DEVICE_TABLE(of, thc63_match);
> > +#endif
> > +
> > +static struct platform_driver thc63_driver = {
> > +	.probe	= thc63_probe,
> > +	.remove	= thc63_remove,
> > +	.driver	= {
> > +		.name		= "thc63lvd1024",
> > +		.of_match_table	= thc63_match,
> > +	},
> > +};
> > +module_platform_driver(thc63_driver);
> > +
> > +MODULE_AUTHOR("Jacopo Mondi <jacopo@...ndi.org>");
> > +MODULE_DESCRIPTION("Thine THC63LVD1024 LVDS decoder DRM bridge driver");
> > +MODULE_LICENSE("GPL v2");
>
>

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