Re: [PATCH 3/5] drm/bridge: Add PTN3460 bridge driver

From: Sean Paul
Date: Thu Oct 03 2013 - 10:58:16 EST

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In reply to: Inki Dae: "Re: [PATCH 3/5] drm/bridge: Add PTN3460 bridge driver"
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On Thu, Oct 3, 2013 at 9:55 AM, Inki Dae <inki.dae@xxxxxxxxxxx> wrote:
> Hi, thank you for your contribution and the below is my short comments,
>
> 2013/10/2 Sean Paul <seanpaul@xxxxxxxxxxxx>:
>> This patch adds a drm_bridge driver for the PTN3460 DisplayPort to LVDS
>> bridge chip.
>>
>> Signed-off-by: Sean Paul <seanpaul@xxxxxxxxxxxx>
>> ---
>> .../devicetree/bindings/drm/bridge/ptn3460.txt | 27 ++
>> drivers/gpu/drm/Kconfig | 2 +
>> drivers/gpu/drm/Makefile | 1 +
>> drivers/gpu/drm/bridge/Kconfig | 4 +
>> drivers/gpu/drm/bridge/Makefile | 3 +
>> drivers/gpu/drm/bridge/ptn3460.c | 349 +++++++++++++++++++++
>> include/drm/bridge/ptn3460.h | 36 +++
>> 7 files changed, 422 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/drm/bridge/ptn3460.txt
>> create mode 100644 drivers/gpu/drm/bridge/Kconfig
>> create mode 100644 drivers/gpu/drm/bridge/Makefile
>> create mode 100644 drivers/gpu/drm/bridge/ptn3460.c
>> create mode 100644 include/drm/bridge/ptn3460.h
>>
>> diff --git a/Documentation/devicetree/bindings/drm/bridge/ptn3460.txt b/Documentation/devicetree/bindings/drm/bridge/ptn3460.txt
>> new file mode 100644
>> index 0000000..c1cd329
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/drm/bridge/ptn3460.txt
>> @@ -0,0 +1,27 @@
>> +ptn3460-bridge bindings
>> +
>> +Required properties:
>> + - compatible: "nxp,ptn3460"
>> + - reg: i2c address of the bridge
>> + - powerdown-gpio: OF device-tree gpio specification
>
> Can a regulator be used instead of gpio in other board case?
>

No, not to my knowledge.

>> + - reset-gpio: OF device-tree gpio specification
>> + - edid-emulation: The EDID emulation entry to use
>> + +-------+------------+------------------+
>> + | Value | Resolution | Description |
>> + | 0 | 1024x768 | NXP Generic |
>> + | 1 | 1920x1080 | NXP Generic |
>> + | 2 | 1920x1080 | NXP Generic |
>> + | 3 | 1600x900 | Samsung LTM200KT |
>> + | 4 | 1920x1080 | Samsung LTM230HT |
>> + | 5 | 1366x768 | NXP Generic |
>> + | 6 | 1600x900 | ChiMei M215HGE |
>> + +-------+------------+------------------+
>> +
>> +Example:
>> + ptn3460-bridge@20 {
>> + compatible = "nxp,ptn3460";
>> + reg = <0x20>;
>> + powerdown-gpio = <&gpy2 5 1 0 0>;
>> + reset-gpio = <&gpx1 5 1 0 0>;
>> + edid-emulation = <5>;
>> + };
>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
>> index 955555d..cd7bfb3 100644
>> --- a/drivers/gpu/drm/Kconfig
>> +++ b/drivers/gpu/drm/Kconfig
>> @@ -236,3 +236,5 @@ source "drivers/gpu/drm/tilcdc/Kconfig"
>> source "drivers/gpu/drm/qxl/Kconfig"
>>
>> source "drivers/gpu/drm/msm/Kconfig"
>> +
>> +source "drivers/gpu/drm/bridge/Kconfig"
>> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
>> index f089adf..9234253 100644
>> --- a/drivers/gpu/drm/Makefile
>> +++ b/drivers/gpu/drm/Makefile
>> @@ -56,3 +56,4 @@ obj-$(CONFIG_DRM_TILCDC) += tilcdc/
>> obj-$(CONFIG_DRM_QXL) += qxl/
>> obj-$(CONFIG_DRM_MSM) += msm/
>> obj-y += i2c/
>> +obj-y += bridge/
>> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
>> new file mode 100644
>> index 0000000..f8db069
>> --- /dev/null
>> +++ b/drivers/gpu/drm/bridge/Kconfig
>> @@ -0,0 +1,4 @@
>> +config DRM_PTN3460
>> + tristate "PTN3460 DP/LVDS bridge"
>> + depends on DRM && I2C
>> + ---help---
>> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
>> new file mode 100644
>> index 0000000..b4733e1
>> --- /dev/null
>> +++ b/drivers/gpu/drm/bridge/Makefile
>> @@ -0,0 +1,3 @@
>> +ccflags-y := -Iinclude/drm
>> +
>> +obj-$(CONFIG_DRM_PTN3460) += ptn3460.o
>> diff --git a/drivers/gpu/drm/bridge/ptn3460.c b/drivers/gpu/drm/bridge/ptn3460.c
>> new file mode 100644
>> index 0000000..a9e5c1a
>> --- /dev/null
>> +++ b/drivers/gpu/drm/bridge/ptn3460.c
>> @@ -0,0 +1,349 @@
>> +/*
>> + * NXP PTN3460 DP/LVDS bridge driver
>> + *
>> + * Copyright (C) 2013 Google, Inc.
>> + *
>> + * This software is licensed under the terms of the GNU General Public
>> + * License version 2, as published by the Free Software Foundation, and
>> + * may be copied, distributed, and modified under those terms.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> + * GNU General Public License for more details.
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/of_gpio.h>
>> +#include <linux/i2c.h>
>> +#include <linux/gpio.h>
>> +#include <linux/delay.h>
>> +
>> +#include "drmP.h"
>> +#include "drm_edid.h"
>> +#include "drm_crtc.h"
>> +#include "drm_crtc_helper.h"
>> +
>> +#include "bridge/ptn3460.h"
>> +
>> +#define PTN3460_EDID_ADDR 0x0
>> +#define PTN3460_EDID_EMULATION_ADDR 0x84
>> +#define PTN3460_EDID_ENABLE_EMULATION 0
>> +#define PTN3460_EDID_EMULATION_SELECTION 1
>> +#define PTN3460_EDID_SRAM_LOAD_ADDR 0x85
>> +
>> +struct ptn3460_bridge {
>> + struct drm_connector connector;
>> + struct i2c_client *client;
>> + struct drm_encoder *encoder;
>> + struct drm_bridge *bridge;
>> + struct edid *edid;
>> + int gpio_pd_n;
>> + int gpio_rst_n;
>> + u32 edid_emulation;
>> + bool enabled;
>> +};
>> +
>> +static int ptn3460_read_bytes(struct ptn3460_bridge *ptn_bridge, char addr,
>> + u8 *buf, int len)
>> +{
>> + int ret;
>> +
>> + ret = i2c_master_send(ptn_bridge->client, &addr, 1);
>> + if (ret <= 0) {
>> + DRM_ERROR("Failed to send i2c command, ret=%d\n", ret);
>> + return ret;
>> + }
>> +
>> + ret = i2c_master_recv(ptn_bridge->client, buf, len);
>> + if (ret <= 0) {
>> + DRM_ERROR("Failed to recv i2c data, ret=%d\n", ret);
>> + return ret;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int ptn3460_write_byte(struct ptn3460_bridge *ptn_bridge, char addr,
>> + char val)
>> +{
>> + int ret;
>> + char buf[2];
>> +
>> + buf[0] = addr;
>> + buf[1] = val;
>> +
>> + ret = i2c_master_send(ptn_bridge->client, buf, ARRAY_SIZE(buf));
>> + if (ret <= 0) {
>> + DRM_ERROR("Failed to send i2c command, ret=%d\n", ret);
>> + return ret;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int ptn3460_select_edid(struct ptn3460_bridge *ptn_bridge)
>> +{
>> + int ret;
>> + char val;
>> +
>> + /* Load the selected edid into SRAM (accessed at PTN3460_EDID_ADDR) */
>> + ret = ptn3460_write_byte(ptn_bridge, PTN3460_EDID_SRAM_LOAD_ADDR,
>> + ptn_bridge->edid_emulation);
>> + if (ret) {
>> + DRM_ERROR("Failed to transfer edid to sram, ret=%d\n", ret);
>> + return ret;
>> + }
>> +
>> + /* Enable EDID emulation and select the desired EDID */
>> + val = 1 << PTN3460_EDID_ENABLE_EMULATION |
>> + ptn_bridge->edid_emulation << PTN3460_EDID_EMULATION_SELECTION;
>> +
>> + ret = ptn3460_write_byte(ptn_bridge, PTN3460_EDID_EMULATION_ADDR, val);
>> + if (ret) {
>> + DRM_ERROR("Failed to write edid value, ret=%d\n", ret);
>> + return ret;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static void ptn3460_pre_enable(struct drm_bridge *bridge)
>> +{
>> + struct ptn3460_bridge *ptn_bridge = bridge->driver_private;
>> + int ret;
>> +
>> + if (ptn_bridge->enabled)
>> + return;
>> +
>> + if (gpio_is_valid(ptn_bridge->gpio_pd_n))
>> + gpio_set_value(ptn_bridge->gpio_pd_n, 1);
>
> Ditto.
>
>> +
>> + if (gpio_is_valid(ptn_bridge->gpio_rst_n)) {
>> + gpio_set_value(ptn_bridge->gpio_rst_n, 0);
>> + udelay(10);
>> + gpio_set_value(ptn_bridge->gpio_rst_n, 1);
>> + }
>> +
>> + /*
>> + * There's a bug in the PTN chip where it falsely asserts hotplug before
>> + * it is fully functional. We're forced to wait for the maximum start up
>> + * time specified in the chip's datasheet to make sure we're really up.
>> + */
>> + msleep(90);
>> +
>> + ret = ptn3460_select_edid(ptn_bridge);
>> + if (ret)
>> + DRM_ERROR("Select edid failed ret=%d\n", ret);
>> +
>> + ptn_bridge->enabled = true;
>> +}
>> +
>> +static void ptn3460_enable(struct drm_bridge *bridge)
>> +{
>> +}
>> +
>> +static void ptn3460_disable(struct drm_bridge *bridge)
>> +{
>> + struct ptn3460_bridge *ptn_bridge = bridge->driver_private;
>> +
>> + if (!ptn_bridge->enabled)
>> + return;
>> +
>> + ptn_bridge->enabled = false;
>> +
>> + if (gpio_is_valid(ptn_bridge->gpio_rst_n))
>> + gpio_set_value(ptn_bridge->gpio_rst_n, 1);
>> +
>> + if (gpio_is_valid(ptn_bridge->gpio_pd_n))
>> + gpio_set_value(ptn_bridge->gpio_pd_n, 0);
>
> Ditto.
>
>> +}
>> +
>> +static void ptn3460_post_disable(struct drm_bridge *bridge)
>> +{
>> +}
>> +
>> +void ptn3460_bridge_destroy(struct drm_bridge *bridge)
>> +{
>> + struct ptn3460_bridge *ptn_bridge = bridge->driver_private;
>> +
>> + drm_bridge_cleanup(bridge);
>> + if (gpio_is_valid(ptn_bridge->gpio_pd_n))
>> + gpio_free(ptn_bridge->gpio_pd_n);
>
> Ditto.
>
>> + if (gpio_is_valid(ptn_bridge->gpio_rst_n))
>> + gpio_free(ptn_bridge->gpio_rst_n);
>> + /* Nothing else to free, we've got devm allocated memory */
>> +}
>> +
>> +struct drm_bridge_funcs ptn3460_bridge_funcs = {
>> + .pre_enable = ptn3460_pre_enable,
>> + .enable = ptn3460_enable,
>> + .disable = ptn3460_disable,
>> + .post_disable = ptn3460_post_disable,
>> + .destroy = ptn3460_bridge_destroy,
>> +};
>> +
>> +int ptn3460_get_modes(struct drm_connector *connector)
>> +{
>> + struct ptn3460_bridge *ptn_bridge;
>> + u8 *edid;
>> + int ret, num_modes;
>> + bool power_off;
>> +
>> + ptn_bridge = container_of(connector, struct ptn3460_bridge, connector);
>> +
>> + if (ptn_bridge->edid)
>> + return drm_add_edid_modes(connector, ptn_bridge->edid);
>> +
>> + power_off = !ptn_bridge->enabled;
>> + ptn3460_pre_enable(ptn_bridge->bridge);
>> +
>> + edid = kmalloc(EDID_LENGTH, GFP_KERNEL);
>> + if (!edid) {
>> + DRM_ERROR("Failed to allocate edid\n");
>> + return 0;
>> + }
>> +
>> + ret = ptn3460_read_bytes(ptn_bridge, PTN3460_EDID_ADDR, edid,
>> + EDID_LENGTH);
>> + if (ret) {
>> + kfree(edid);
>> + num_modes = 0;
>> + goto out;
>> + }
>> +
>> + ptn_bridge->edid = (struct edid *)edid;
>> + drm_mode_connector_update_edid_property(connector, ptn_bridge->edid);
>> +
>> + num_modes = drm_add_edid_modes(connector, ptn_bridge->edid);
>> +
>> +out:
>> + if (power_off)
>> + ptn3460_disable(ptn_bridge->bridge);
>> +
>> + return num_modes;
>> +}
>> +
>> +static int ptn3460_mode_valid(struct drm_connector *connector,
>> + struct drm_display_mode *mode)
>> +{
>> + return MODE_OK;
>> +}
>> +
>> +struct drm_encoder *ptn3460_best_encoder(struct drm_connector *connector)
>> +{
>> + struct ptn3460_bridge *ptn_bridge;
>> +
>> + ptn_bridge = container_of(connector, struct ptn3460_bridge, connector);
>> +
>> + return ptn_bridge->encoder;
>> +}
>> +
>> +struct drm_connector_helper_funcs ptn3460_connector_helper_funcs = {
>> + .get_modes = ptn3460_get_modes,
>> + .mode_valid = ptn3460_mode_valid,
>> + .best_encoder = ptn3460_best_encoder,
>> +};
>> +
>> +enum drm_connector_status ptn3460_detect(struct drm_connector *connector,
>> + bool force)
>> +{
>> + return connector_status_connected;
>> +}
>> +
>> +void ptn3460_connector_destroy(struct drm_connector *connector)
>> +{
>> + drm_connector_cleanup(connector);
>> +}
>> +
>> +struct drm_connector_funcs ptn3460_connector_funcs = {
>> + .dpms = drm_helper_connector_dpms,
>> + .fill_modes = drm_helper_probe_single_connector_modes,
>> + .detect = ptn3460_detect,
>> + .destroy = ptn3460_connector_destroy,
>> +};
>
> Why do you try to add a new connector here? We already have the
> connector for LCD, and also provides some callbacks for it. For this,
> please see exynos_drm_display_ops of exynos_drm_fimd driver, and you
> can add new callbacks to there such as init callback for bridge device
> initialization if needed.
>

We add a new connector for 2 reasons:

1) We need to override the drm detect() callback to always return true
since the DP driver will presumably return its hotplug status which
will always be low when the ptn chip is turned off.
2) We want the ability to control the result of get_modes().

I've got a patch set almost ready to tear the display ops out of fimd
and put them in the DP driver. The display ops are better suited
there, since it's the actual encoder/connector. I hope to get that
posted this week.

>> +
>> +int ptn3460_init(struct drm_device *dev, struct drm_encoder *encoder,
>> + struct i2c_client *client, struct device_node *node)
>> +{
>> + int ret;
>> + struct drm_bridge *bridge;
>> + struct ptn3460_bridge *ptn_bridge;
>> +
>> + bridge = devm_kzalloc(dev->dev, sizeof(*bridge), GFP_KERNEL);
>> + if (!bridge) {
>> + DRM_ERROR("Failed to allocate drm bridge\n");
>> + return -ENOMEM;
>> + }
>> +
>> + ptn_bridge = devm_kzalloc(dev->dev, sizeof(*ptn_bridge), GFP_KERNEL);
>> + if (!ptn_bridge) {
>> + DRM_ERROR("Failed to allocate ptn bridge\n");
>> + return -ENOMEM;
>> + }
>> +
>> + ptn_bridge->client = client;
>> + ptn_bridge->encoder = encoder;
>> + ptn_bridge->bridge = bridge;
>> + ptn_bridge->gpio_pd_n = of_get_named_gpio(node, "powerdown-gpio", 0);
>
> Also, if a regulator is used instead?
>
>> + if (gpio_is_valid(ptn_bridge->gpio_pd_n)) {
>> + ret = gpio_request_one(ptn_bridge->gpio_pd_n,
>> + GPIOF_OUT_INIT_HIGH, "PTN3460_PD_N");
>> + if (ret) {
>> + DRM_ERROR("Request powerdown-gpio failed (%d)\n", ret);
>> + return ret;
>> + }
>> + }
>> +
>> + ptn_bridge->gpio_rst_n = of_get_named_gpio(node, "reset-gpio", 0);
>> + if (gpio_is_valid(ptn_bridge->gpio_rst_n)) {
>> + /*
>> + * Request the reset pin low to avoid the bridge being
>> + * initialized prematurely
>> + */
>> + ret = gpio_request_one(ptn_bridge->gpio_rst_n,
>> + GPIOF_OUT_INIT_LOW, "PTN3460_RST_N");
>> + if (ret) {
>> + DRM_ERROR("Request reset-gpio failed (%d)\n", ret);
>> + gpio_free(ptn_bridge->gpio_pd_n);
>> + return ret;
>> + }
>> + }
>> +
>> + ret = of_property_read_u32(node, "edid-emulation",
>> + &ptn_bridge->edid_emulation);
>> + if (ret) {
>> + DRM_ERROR("Can't read edid emulation value\n");
>> + goto err;
>> + }
>> +
>> + ret = drm_bridge_init(dev, bridge, &ptn3460_bridge_funcs);
>> + if (ret) {
>> + DRM_ERROR("Failed to initialize bridge with drm\n");
>> + goto err;
>> + }
>> +
>> + bridge->driver_private = ptn_bridge;
>> + encoder->bridge = bridge;
>> +
>> + ret = drm_connector_init(dev, &ptn_bridge->connector,
>> + &ptn3460_connector_funcs, DRM_MODE_CONNECTOR_LVDS);
>
> So it seems that here's not right place to call drm_connector_init function.
>
> Display pipeline path could be one of,
> Display Controller Display bus
> ---------------------------------------------------------------------------
> FIMD---------------------LVDS--------------------LCD,
> or
> FIMD----------------------eDP---------------------LCD,
> or
> FIMD------------------MIPI-DSI------------------LCD,
> or
> FIMD-------------------------------------------------LCD
>
> And also in case using image enhancement chip,
> mDNIe-------------FIMD-LITE between Display Controller and Display
> bus.
>
> So, wouldn't the right place below FIMD driver? :)
>

Well, this driver should be considered outside of exynos context since
it could be used by any drm driver.

In the exynos context, the right place to implement it would be in the
dp driver, actually. However, the exynos driver has a level of
abstraction on top of the crtcs/encoders such that we need to
initialize it in the exynos_drm_core. The patchset I mentioned above
should help move things in a direction where fimd/mixer implement
drm_crtc directly and hdmi/dp implement drm_encoder/drm_connector
directly. In that world, DP would initialize the ptn driver.

>
>> + if (ret) {
>> + DRM_ERROR("Failed to initialize connector with drm\n");
>> + goto err;
>> + }
>> + drm_connector_helper_add(&ptn_bridge->connector,
>> + &ptn3460_connector_helper_funcs);
>> + drm_sysfs_connector_add(&ptn_bridge->connector);
>> + drm_mode_connector_attach_encoder(&ptn_bridge->connector, encoder);
>> +
>> + return 0;
>> +
>> +err:
>> + if (gpio_is_valid(ptn_bridge->gpio_pd_n))
>> + gpio_free(ptn_bridge->gpio_pd_n);
>> + if (gpio_is_valid(ptn_bridge->gpio_rst_n))
>> + gpio_free(ptn_bridge->gpio_rst_n);
>> + return ret;
>> +}
>> diff --git a/include/drm/bridge/ptn3460.h b/include/drm/bridge/ptn3460.h
>> new file mode 100644
>> index 0000000..157ffa1
>> --- /dev/null
>> +++ b/include/drm/bridge/ptn3460.h
>> @@ -0,0 +1,36 @@
>> +/*
>> + * Copyright (C) 2013 Google, Inc.
>> + *
>> + * This software is licensed under the terms of the GNU General Public
>> + * License version 2, as published by the Free Software Foundation, and
>> + * may be copied, distributed, and modified under those terms.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> + * GNU General Public License for more details.
>> + */
>> +
>> +#ifndef _DRM_BRIDGE_PTN3460_H_
>> +#define _DRM_BRIDGE_PTN3460_H_
>> +
>> +struct drm_device;
>> +struct drm_encoder;
>> +struct i2c_client;
>> +struct device_node;
>> +
>> +#ifdef CONFIG_DRM_PTN3460
>> +
>> +int ptn3460_init(struct drm_device *dev, struct drm_encoder *encoder,
>> + struct i2c_client *client, struct device_node *node);
>> +#else
>> +
>> +int ptn3460_init(struct drm_device *dev, struct drm_encoder *encoder,
>> + struct i2c_client *client, struct device_node *node)
>> +{
>> + return 0;
>> +}
>> +
>> +#endif
>> +
>> +#endif
>> --
>> 1.8.4
>>
>>
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