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References: <20210218210504.375752-1-adrien.grassein@gmail.com> <20210218210504.375752-3-adrien.grassein@gmail.com>
In-Reply-To: <20210218210504.375752-3-adrien.grassein@gmail.com>
From:   Robert Foss <robert.foss@linaro.org>
Date:   Fri, 19 Feb 2021 14:27:36 +0100
Message-ID: <CAG3jFyuQHxS9mc2k=1GSgwR40r8xbZ9wYguBYhQy8Sb4ma3gxA@mail.gmail.com>
Subject: Re: [PATCH v3 2/2] drm/bridge: Introduce LT8912 DSI to HDMI bridge
To:     Adrien Grassein <adrien.grassein@gmail.com>
Cc:     David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Rob Herring <robh+dt@kernel.org>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@siol.net>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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Hey Adrien,


Thanks for the quick update.

On Thu, 18 Feb 2021 at 22:05, Adrien Grassein <adrien.grassein@gmail.com> wrote:
>
> Lontium Lt8912 is a DSI to HDMI bridge.
>
> Signed-off-by: Adrien Grassein <adrien.grassein@gmail.com>
> ---
>  MAINTAINERS                             |   1 +
>  drivers/gpu/drm/bridge/Kconfig          |  14 +
>  drivers/gpu/drm/bridge/Makefile         |   1 +
>  drivers/gpu/drm/bridge/lontium-lt8912.c | 760 ++++++++++++++++++++++++
>  4 files changed, 776 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/lontium-lt8912.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 5d1ed281cd41..58f8f45a7c86 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -10462,6 +10462,7 @@ LONTIUM LT8912 MIPI TO HDMI BRIDGE
>  M:     Adrien Grassein <adrien.grassein@gmail.com>
>  S:     Maintained
>  F:     Documentation/devicetree/bindings/display/bridge/lontium,lt8912.yaml
> +F:     drivers/gpu/drm/bridge/lontium-lt8912.c
>
>  LSILOGIC MPT FUSION DRIVERS (FC/SAS/SPI)
>  M:     Sathya Prakash <sathya.prakash@broadcom.com>
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index e4110d6ca7b3..5b36d4b86e3c 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -48,6 +48,20 @@ config DRM_DISPLAY_CONNECTOR
>           on ARM-based platforms. Saying Y here when this driver is not needed
>           will not cause any issue.
>
> +config DRM_LONTIUM_LT8912
> +       tristate "Lontium LT8912 DSI/HDMI bridge"
> +       depends on OF
> +       select DRM_PANEL_BRIDGE
> +       select DRM_KMS_HELPER
> +       select REGMAP_I2C
> +       help
> +         Driver for Lontium LT8912 DSI to HDMI bridge
> +         chip driver.
> +         Please say Y if you have such hardware.
> +
> +         Say M here if you want to support this hardware as a module.
> +         The module will be named "lontium-lt8912".
> +
>  config DRM_LONTIUM_LT9611
>         tristate "Lontium LT9611 DSI/HDMI bridge"
>         select SND_SOC_HDMI_CODEC if SND_SOC
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 86e7acc76f8d..5a1b201cea1f 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -2,6 +2,7 @@
>  obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
>  obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
>  obj-$(CONFIG_DRM_DISPLAY_CONNECTOR) += display-connector.o
> +obj-$(CONFIG_DRM_LONTIUM_LT8912) += lontium-lt8912.o
>  obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
>  obj-$(CONFIG_DRM_LONTIUM_LT9611UXC) += lontium-lt9611uxc.o
>  obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
> diff --git a/drivers/gpu/drm/bridge/lontium-lt8912.c b/drivers/gpu/drm/bridge/lontium-lt8912.c
> new file mode 100644
> index 000000000000..8bdb584d22ce
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/lontium-lt8912.c
> @@ -0,0 +1,760 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2018, The Linux Foundation. All rights reserved.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/gpio.h>
> +#include <linux/of_gpio.h>
> +#include <linux/regmap.h>
> +
> +#include <drm/drm_probe_helper.h>
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_mipi_dsi.h>
> +#include <drm/drm_of.h>
> +
> +#include <video/videomode.h>
> +
> +#define I2C_MAIN 0
> +#define I2C_ADDR_MAIN 0x48
> +
> +#define I2C_CEC_DSI 1
> +#define I2C_ADDR_CEC_DSI 0x49
> +
> +#define I2C_MAX_IDX 2
> +
> +struct lt8912 {
> +       struct device *dev;
> +       struct drm_bridge bridge;
> +       struct drm_connector connector;
> +
> +       struct i2c_client *i2c_client[I2C_MAX_IDX];
> +       struct regmap *regmap[I2C_MAX_IDX];
> +
> +       struct device_node *host_node;
> +       struct drm_bridge *hdmi_port;
> +
> +       struct mipi_dsi_device *dsi;
> +
> +       struct gpio_desc *gp_reset;
> +
> +       struct videomode mode;
> +
> +       u8 data_lanes;
> +       bool is_power_on;
> +       bool is_attached;
> +};
> +
> +static int lt8912_write_init_config(struct lt8912 *lt)
> +{
> +       const struct reg_sequence seq[] = {
> +               /* Digital clock en*/
> +               {0x08, 0xff},
> +               {0x09, 0xff},
> +               {0x0a, 0xff},
> +               {0x0b, 0x7c},
> +               {0x0c, 0xff},
> +               {0x42, 0x04},
> +
> +               /*Tx Analog*/
> +               {0x31, 0xb1},
> +               {0x32, 0xb1},
> +               {0x33, 0x0e},
> +               {0x37, 0x00},
> +               {0x38, 0x22},
> +               {0x60, 0x82},
> +
> +               /*Cbus Analog*/
> +               {0x39, 0x45},
> +               {0x3a, 0x00},
> +               {0x3b, 0x00},
> +
> +               /*HDMI Pll Analog*/
> +               {0x44, 0x31},
> +               {0x55, 0x44},
> +               {0x57, 0x01},
> +               {0x5a, 0x02},
> +
> +               /*MIPI Analog*/
> +               {0x3e, 0xd6},
> +               {0x3f, 0xd4},
> +               {0x41, 0x3c},
> +               {0xB2, 0x00},
> +       };
> +
> +       return regmap_multi_reg_write(lt->regmap[I2C_MAIN], seq, ARRAY_SIZE(seq));
> +}
> +
> +static int lt8912_write_mipi_basic_config(struct lt8912 *lt)
> +{
> +       const struct reg_sequence seq[] = {
> +               {0x12, 0x04},
> +               {0x14, 0x00},
> +               {0x15, 0x00},
> +               {0x1a, 0x03},
> +               {0x1b, 0x03},
> +       };
> +
> +       return regmap_multi_reg_write(lt->regmap[I2C_CEC_DSI], seq, ARRAY_SIZE(seq));
> +};
> +
> +static int lt8912_write_dds_config(struct lt8912 *lt)
> +{
> +       const struct reg_sequence seq[] = {
> +               {0x4e, 0xff},
> +               {0x4f, 0x56},
> +               {0x50, 0x69},
> +               {0x51, 0x80},
> +               {0x1f, 0x5e},
> +               {0x20, 0x01},
> +               {0x21, 0x2c},
> +               {0x22, 0x01},
> +               {0x23, 0xfa},
> +               {0x24, 0x00},
> +               {0x25, 0xc8},
> +               {0x26, 0x00},
> +               {0x27, 0x5e},
> +               {0x28, 0x01},
> +               {0x29, 0x2c},
> +               {0x2a, 0x01},
> +               {0x2b, 0xfa},
> +               {0x2c, 0x00},
> +               {0x2d, 0xc8},
> +               {0x2e, 0x00},
> +               {0x42, 0x64},
> +               {0x43, 0x00},
> +               {0x44, 0x04},
> +               {0x45, 0x00},
> +               {0x46, 0x59},
> +               {0x47, 0x00},
> +               {0x48, 0xf2},
> +               {0x49, 0x06},
> +               {0x4a, 0x00},
> +               {0x4b, 0x72},
> +               {0x4c, 0x45},
> +               {0x4d, 0x00},
> +               {0x52, 0x08},
> +               {0x53, 0x00},
> +               {0x54, 0xb2},
> +               {0x55, 0x00},
> +               {0x56, 0xe4},
> +               {0x57, 0x0d},
> +               {0x58, 0x00},
> +               {0x59, 0xe4},
> +               {0x5a, 0x8a},
> +               {0x5b, 0x00},
> +               {0x5c, 0x34},
> +               {0x1e, 0x4f},
> +               {0x51, 0x00},
> +       };
> +
> +       return regmap_multi_reg_write(lt->regmap[I2C_CEC_DSI], seq, ARRAY_SIZE(seq));
> +}
> +
> +static int lt8912_write_rxlogicres_config(struct lt8912 *lt)
> +{
> +       int ret;
> +
> +       ret = regmap_write(lt->regmap[I2C_MAIN], 0x03, 0x7f);
> +       usleep_range(10000, 20000);
> +       ret |= regmap_write(lt->regmap[I2C_MAIN], 0x03, 0xff);
> +
> +       return ret;
> +};
> +
> +static int lt8912_write_lvds_config(struct lt8912 *lt)
> +{
> +       const struct reg_sequence seq[] = {
> +               {0x44, 0x30},
> +               {0x51, 0x05},
> +               {0x50, 0x24},
> +               {0x51, 0x2d},
> +               {0x52, 0x04},
> +               {0x69, 0x0e},
> +               {0x69, 0x8e},
> +               {0x6a, 0x00},
> +               {0x6c, 0xb8},
> +               {0x6b, 0x51},
> +               {0x04, 0xfb},
> +               {0x04, 0xff},
> +               {0x7f, 0x00},
> +               {0xa8, 0x13},
> +               {0x02, 0xf7},
> +               {0x02, 0xff},
> +               {0x03, 0xcf},
> +               {0x03, 0xff},
> +       };
> +
> +       return regmap_multi_reg_write(lt->regmap[I2C_CEC_DSI], seq, ARRAY_SIZE(seq));
> +};
> +
> +static inline struct lt8912 *bridge_to_lt8912(struct drm_bridge *b)
> +{
> +       return container_of(b, struct lt8912, bridge);
> +}
> +
> +static inline struct lt8912 *connector_to_lt8912(struct drm_connector *c)
> +{
> +       return container_of(c, struct lt8912, connector);
> +}
> +
> +static const struct regmap_config lt8912_regmap_config = {
> +       .reg_bits = 8,
> +       .val_bits = 8,
> +       .max_register = 0xff,
> +};
> +
> +static int lt8912_init_i2c(struct lt8912 *lt)
> +{
> +       unsigned int i;
> +       int ret;
> +       /*
> +        * At this time we only initialize 2 chips, but the lt8912 provides
> +        * a third interface for the audio over HDMI configuration.
> +        */
> +       struct i2c_board_info info[] = {
> +               { I2C_BOARD_INFO("lt8912p0", I2C_ADDR_MAIN), },
> +               { I2C_BOARD_INFO("lt8912p1", I2C_ADDR_CEC_DSI), },
> +       };
> +
> +       if (!lt)
> +               return -ENODEV;
> +
> +       for (i = 0; i < ARRAY_SIZE(info); i++) {
> +               /*
> +                * lt->i2c_client[0] was already allocated earlier by the
> +                * kernel (via DT).
> +                */
> +               if (i > 0) {
> +                       lt->i2c_client[i] = i2c_new_dummy_device(lt->i2c_client[0]->adapter,
> +                                                                info[i].addr);
> +                       if (!lt->i2c_client[i])
> +                               return -ENODEV;
> +               }
> +               lt->regmap[i] = devm_regmap_init_i2c(lt->i2c_client[i],
> +                                                    &lt8912_regmap_config);
> +               if (IS_ERR(lt->regmap[i])) {
> +                       ret = PTR_ERR(lt->regmap[i]);
> +                       return ret;
> +               }
> +       }
> +       return 0;
> +}

I had a 2nd look at prior art for bridges with multiple I2C addresses,
and I think I prefer the implementation in anx7625. Instead of having
one I2C address provided by the DT and one by the driver, all are
provided by the driver. If you have any even better suggestions, I'd
be curious to hear them.

https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/bridge/analogix/anx7625.c#L1646

> +
> +static int lt8912_free_i2c(struct lt8912 *lt)
> +{
> +       unsigned int i;
> +
> +       for (i = 1; i < I2C_MAX_IDX; i++)
> +               i2c_unregister_device(lt->i2c_client[i]);
> +
> +       return 0;
> +}
> +
> +static int lt8912_hard_power_on(struct lt8912 *lt)
> +{
> +       gpiod_set_value_cansleep(lt->gp_reset, 0);
> +       msleep(20);
> +
> +       return 0;
> +}
> +
> +static void lt8912_hard_power_off(struct lt8912 *lt)
> +{
> +       gpiod_set_value_cansleep(lt->gp_reset, 1);
> +       msleep(20);
> +       lt->is_power_on = false;
> +}
> +
> +static int lt8912_video_setup(struct lt8912 *lt)
> +{
> +       u32 hactive, h_total, hpw, hfp, hbp;
> +       u32 vactive, v_total, vpw, vfp, vbp;
> +       u8 settle = 0x08;
> +       int ret;
> +
> +       if (!lt)
> +               return -EINVAL;
> +
> +       hactive = lt->mode.hactive;
> +       hfp = lt->mode.hfront_porch;
> +       hpw = lt->mode.hsync_len;
> +       hbp = lt->mode.hback_porch;
> +       h_total = hactive + hfp + hpw + hbp;
> +
> +       vactive = lt->mode.vactive;
> +       vfp = lt->mode.vfront_porch;
> +       vpw = lt->mode.vsync_len;
> +       vbp = lt->mode.vback_porch;
> +       v_total = vactive + vfp + vpw + vbp;
> +
> +       if (vactive <= 600)
> +               settle = 0x04;
> +       else if (vactive == 1080)
> +               settle = 0x0a;
> +
> +       ret = regmap_write(lt->regmap[I2C_CEC_DSI], 0x10, 0x01);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x11, settle);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x18, hpw);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x19, vpw);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x1c, hactive & 0xff);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x1d, hactive >> 8);
> +
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x2f, 0x0c);
> +
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x34, h_total & 0xff);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x35, h_total >> 8);
> +
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x36, v_total & 0xff);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x37, v_total >> 8);
> +
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x38, vbp & 0xff);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x39, vbp >> 8);
> +
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x3a, vfp & 0xff);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x3b, vfp >> 8);
> +
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x3c, hbp & 0xff);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x3d, hbp >> 8);
> +
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x3e, hfp & 0xff);
> +       ret |= regmap_write(lt->regmap[I2C_CEC_DSI], 0x3f, hfp >> 8);
> +
> +       return ret;
> +}
> +
> +static int lt8912_soft_power_on(struct lt8912 *lt)
> +{
> +       if (!lt->is_power_on) {
> +               u32 lanes = lt->data_lanes;
> +
> +               lt8912_write_init_config(lt);
> +               regmap_write(lt->regmap[I2C_CEC_DSI], 0x13, lanes & 3);
> +
> +               lt8912_write_mipi_basic_config(lt);
> +
> +               lt->is_power_on = true;
> +       }
> +
> +       return 0;
> +}
> +
> +static int lt8912_video_on(struct lt8912 *lt)
> +{
> +       int ret;
> +
> +       ret = lt8912_video_setup(lt);
> +       if (ret < 0)
> +               goto end;
> +
> +       ret = lt8912_write_dds_config(lt);
> +       if (ret < 0)
> +               goto end;
> +
> +       ret = lt8912_write_rxlogicres_config(lt);
> +       if (ret < 0)
> +               goto end;
> +
> +       ret = lt8912_write_lvds_config(lt);
> +       if (ret < 0)
> +               goto end;
> +
> +end:
> +       return ret;
> +}
> +
> +static enum drm_connector_status
> +lt8912_connector_detect(struct drm_connector *connector, bool force)
> +{
> +       struct lt8912 *lt = connector_to_lt8912(connector);
> +
> +       return drm_bridge_detect(lt->hdmi_port);
> +}
> +
> +static const struct drm_connector_funcs lt8912_connector_funcs = {
> +       .detect = lt8912_connector_detect,
> +       .fill_modes = drm_helper_probe_single_connector_modes,
> +       .destroy = drm_connector_cleanup,
> +       .reset = drm_atomic_helper_connector_reset,
> +       .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> +       .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> +};
> +
> +static enum drm_mode_status
> +lt8912_connector_mode_valid(struct drm_connector *connector,
> +                           struct drm_display_mode *mode)
> +{
> +       if (mode->clock > 150000)
> +               return MODE_CLOCK_HIGH;
> +
> +       if (mode->hdisplay > 1920)
> +               return MODE_BAD_HVALUE;
> +
> +       if (mode->vdisplay > 1080)
> +               return MODE_BAD_VVALUE;
> +
> +       return MODE_OK;
> +}
> +
> +static int lt8912_connector_get_modes(struct drm_connector *connector)
> +{
> +       struct edid *edid;
> +       int ret, num = 0;
> +       struct lt8912 *lt = connector_to_lt8912(connector);
> +       u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24;
> +
> +       edid = drm_bridge_get_edid(lt->hdmi_port, connector);
> +       if (edid) {
> +               drm_connector_update_edid_property(connector, edid);
> +               num = drm_add_edid_modes(connector, edid);
> +       } else
> +               return ret;
> +
> +       ret = drm_display_info_set_bus_formats(&connector->display_info,
> +                                              &bus_format, 1);
> +       if (ret)
> +               num = ret;
> +
> +       kfree(edid);
> +       return num;
> +}
> +
> +static const struct drm_connector_helper_funcs lt8912_connector_helper_funcs = {
> +       .get_modes = lt8912_connector_get_modes,
> +       .mode_valid = lt8912_connector_mode_valid,
> +};
> +
> +static void lt8912_bridge_mode_set(struct drm_bridge *bridge,
> +                                  const struct drm_display_mode *mode,
> +                                  const struct drm_display_mode *adj)
> +{
> +       struct lt8912 *lt = bridge_to_lt8912(bridge);
> +
> +       drm_display_mode_to_videomode(adj, &lt->mode);
> +}
> +
> +static void lt8912_bridge_enable(struct drm_bridge *bridge)
> +{
> +       struct lt8912 *lt = bridge_to_lt8912(bridge);
> +
> +       lt8912_video_on(lt);
> +}
> +
> +static int lt8912_attach_dsi(struct lt8912 *lt)
> +{
> +       struct device *dev = lt->dev;
> +       struct mipi_dsi_host *host;
> +       struct mipi_dsi_device *dsi;
> +       int ret = -1;
> +       const struct mipi_dsi_device_info info = { .type = "lt8912",
> +                                                  .channel = 0,
> +                                                  .node = NULL,
> +                                                };
> +
> +       host = of_find_mipi_dsi_host_by_node(lt->host_node);
> +       if (!host) {
> +               dev_err(dev, "failed to find dsi host\n");
> +               return -EPROBE_DEFER;
> +       }
> +
> +       dsi = mipi_dsi_device_register_full(host, &info);
> +       if (IS_ERR(dsi)) {
> +               ret = PTR_ERR(dsi);
> +               dev_err(dev, "failed to create dsi device (%d)\n", ret);
> +               goto err_dsi_device;
> +       }
> +
> +       lt->dsi = dsi;
> +
> +       dsi->lanes = lt->data_lanes;
> +       dsi->format = MIPI_DSI_FMT_RGB888;
> +
> +       dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
> +                         MIPI_DSI_MODE_VIDEO_BURST |
> +                         MIPI_DSI_MODE_LPM |
> +                         MIPI_DSI_MODE_EOT_PACKET;
> +
> +       ret = mipi_dsi_attach(dsi);
> +       if (ret < 0) {
> +               dev_err(dev, "failed to attach dsi to host\n");
> +               goto err_dsi_attach;
> +       }
> +
> +       return 0;
> +
> +err_dsi_attach:
> +       mipi_dsi_device_unregister(dsi);
> +err_dsi_device:
> +       return ret;
> +}
> +
> +static void lt8912_detach_dsi(struct lt8912 *lt)
> +{
> +       mipi_dsi_detach(lt->dsi);
> +       mipi_dsi_device_unregister(lt->dsi);
> +}
> +
> +static void lt8912_bridge_connector_hpd_event(void *arg,
> +                                             enum drm_connector_status status)
> +{
> +       struct lt8912 *lt = arg;
> +
> +       if (lt->hdmi_port->dev)
> +               drm_helper_hpd_irq_event(lt->hdmi_port->dev);
> +}
> +
> +static int lt8912_bridge_connector_init(struct drm_bridge *bridge)
> +{
> +       int ret;
> +       struct lt8912 *lt = bridge_to_lt8912(bridge);
> +       struct drm_connector *connector = &lt->connector;
> +
> +       if (lt->hdmi_port->ops & DRM_BRIDGE_OP_DETECT) {
> +               connector->polled = DRM_CONNECTOR_POLL_HPD;
> +       } else {
> +               connector->polled = DRM_CONNECTOR_POLL_CONNECT |
> +                                   DRM_CONNECTOR_POLL_DISCONNECT;
> +       }
> +
> +       if (lt->hdmi_port->ops & DRM_BRIDGE_OP_HPD) {
> +               drm_bridge_hpd_enable(lt->hdmi_port,
> +                                     lt8912_bridge_connector_hpd_event,
> +                                     lt);
> +       }
> +
> +       ret = drm_connector_init(bridge->dev, connector,
> +                                &lt8912_connector_funcs,
> +                                lt->hdmi_port->type);
> +       if (ret)
> +               goto exit;
> +
> +       drm_connector_helper_add(connector, &lt8912_connector_helper_funcs);
> +
> +       connector->dpms = DRM_MODE_DPMS_OFF;
> +       drm_connector_attach_encoder(connector, bridge->encoder);
> +exit:
> +       return ret;
> +}
> +
> +static int lt8912_bridge_attach(struct drm_bridge *bridge,
> +                               enum drm_bridge_attach_flags flags)
> +{
> +       struct lt8912 *lt = bridge_to_lt8912(bridge);
> +       int ret;
> +
> +       if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
> +               ret = lt8912_bridge_connector_init(bridge);
> +               if (ret) {
> +                       dev_err(lt->dev, "Failed to init bridge ! (%d)\n", ret);
> +                       return ret;
> +               }
> +       }
> +
> +
> +       ret = lt8912_hard_power_on(lt);
> +       if (ret)
> +               return ret;
> +
> +       ret = lt8912_soft_power_on(lt);
> +       if (ret)
> +               goto error;
> +
> +       ret = lt8912_attach_dsi(lt);
> +       if (ret)
> +               goto error;
> +
> +       lt->is_attached = true;
> +
> +       return 0;
> +
> +error:
> +       lt8912_hard_power_off(lt);
> +       return ret;
> +}
> +
> +static void lt8912_bridge_detach(struct drm_bridge *bridge)
> +{
> +       struct lt8912 *lt = bridge_to_lt8912(bridge);
> +
> +       if (lt->is_attached) {
> +               if (lt->hdmi_port->ops & DRM_BRIDGE_OP_HPD)
> +                       drm_bridge_hpd_disable(lt->hdmi_port);
> +               lt8912_detach_dsi(lt);
> +               lt8912_hard_power_off(lt);
> +       }
> +}
> +
> +static enum drm_connector_status
> +lt8912_bridge_detect(struct drm_bridge *bridge)
> +{
> +       struct lt8912 *lt = bridge_to_lt8912(bridge);
> +
> +       return drm_bridge_detect(lt->hdmi_port);
> +}
> +
> +static struct edid *lt8912_bridge_get_edid(struct drm_bridge *bridge,
> +                                              struct drm_connector *connector)
> +{
> +       struct lt8912 *lt = bridge_to_lt8912(bridge);
> +
> +       return drm_bridge_get_edid(lt->hdmi_port, connector);
> +}
> +
> +static const struct drm_bridge_funcs lt8912_bridge_funcs = {
> +       .attach = lt8912_bridge_attach,
> +       .detach = lt8912_bridge_detach,
> +       .mode_set = lt8912_bridge_mode_set,
> +       .enable = lt8912_bridge_enable,
> +       .detect = lt8912_bridge_detect,
> +       .get_edid = lt8912_bridge_get_edid,
> +};
> +
> +static int lt8912_parse_dt(struct lt8912 *lt)
> +{
> +       struct gpio_desc *gp_reset;
> +       struct device *dev = lt->dev;
> +       int ret = 0;
> +       struct device_node *port_node;
> +       struct device_node *endpoint;
> +
> +       gp_reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
> +       if (IS_ERR(gp_reset)) {
> +               ret = PTR_ERR(gp_reset);
> +               if (ret != -EPROBE_DEFER)
> +                       dev_err(dev, "Failed to get reset gpio: %d\n", ret);
> +               return ret;
> +       }
> +       lt->gp_reset = gp_reset;
> +
> +
> +       endpoint = of_graph_get_endpoint_by_regs(dev->of_node, 0, -1);
> +       if (IS_ERR(endpoint)) {
> +               ret = PTR_ERR(endpoint);
> +               goto end;
> +       }
> +
> +       lt->data_lanes = of_property_count_u32_elems(endpoint, "data-lanes");
> +       of_node_put(endpoint);
> +
> +       lt->host_node = of_graph_get_remote_node(dev->of_node, 0, -1);
> +       if (!lt->host_node) {
> +               dev_err(lt->dev, "%s: Failed to get remote port\n", __func__);
> +               ret = -ENODEV;
> +               goto end;
> +       }
> +
> +       port_node = of_graph_get_remote_node(dev->of_node, 1, -1);
> +       if (!port_node) {
> +               dev_err(lt->dev, "%s: Failed to get connector port\n", __func__);
> +               ret = -ENODEV;
> +               goto err_free_host_node;
> +       }
> +
> +       lt->hdmi_port = of_drm_find_bridge(port_node);
> +       if (IS_ERR(lt->hdmi_port)) {
> +               dev_err(lt->dev, "%s: Failed to get hdmi port\n", __func__);
> +               ret = PTR_ERR(lt->hdmi_port);
> +               of_node_put(lt->host_node);
> +               goto end;
> +       }
> +
> +       if (!of_device_is_compatible(port_node, "hdmi-connector")) {
> +               dev_err(lt->dev, "%s: Failed to get hdmi port\n", __func__);
> +               ret = -EINVAL;
> +       }
> +
> +       of_node_put(port_node);
> +
> +end:
> +       return ret;
> +
> +err_free_host_node:
> +       of_node_put(lt->host_node);
> +       return ret;
> +}
> +
> +static int lt8912_put_dt(struct lt8912 *lt)
> +{
> +       of_node_put(lt->host_node);
> +       return 0;
> +}
> +
> +static int lt8912_probe(struct i2c_client *client,
> +        const struct i2c_device_id *id)
> +{
> +       static struct lt8912 *lt;
> +       int ret = 0;
> +       struct device *dev = &client->dev;
> +
> +       lt = devm_kzalloc(dev, sizeof(struct lt8912), GFP_KERNEL);
> +       if (!lt)
> +               return -ENOMEM;
> +
> +       lt->dev = dev;
> +       lt->i2c_client[0] = client;
> +
> +       ret = lt8912_parse_dt(lt);
> +       if (ret)
> +               goto err_dt_parse;
> +
> +       ret = lt8912_init_i2c(lt);
> +       if (ret)
> +               goto err_i2c;
> +
> +       i2c_set_clientdata(client, lt);
> +
> +       lt->bridge.funcs = &lt8912_bridge_funcs;
> +       lt->bridge.of_node = dev->of_node;
> +       lt->bridge.ops = lt->hdmi_port->ops;

This is not entirely kosher, bridge.ops should mirror what is
implemented by bridge.funcs.

I would expect DRM_BRIDGE_OP_HPD and possibly DRM_BRIDGE_OP_DETECT to
be enabled, since the hardware brief mentions supporting hot plug
detection.
drm_bridge_funcs.hpd_enable & drm_bridge_funcs.hpd_disable should both
also be implemented. If the hardware supports HPD, the driver is
required to support it as well.

lt8912_product_brief.pdf: https://allg.one/0R71

Have you seen the lt8912 driver in the Toradex tree? It mentions HPD
and the relevant registers, but doesn't implement support for it

http://git.toradex.com/cgit/linux-toradex.git/tree/drivers/gpu/drm/bridge/lt8912.c?h=colibri&id=331ac1cf6e09d90e7d9ab39445bc8812ff33f178#n248

> +
> +       drm_bridge_add(&lt->bridge);
> +
> +       return 0;
> +
> +err_i2c:
> +       lt8912_put_dt(lt);
> +err_dt_parse:
> +       return ret;
> +}
> +
> +static int lt8912_remove(struct i2c_client *client)
> +{
> +       struct lt8912 *lt = i2c_get_clientdata(client);
> +
> +       lt8912_bridge_detach(&lt->bridge);
> +       drm_bridge_remove(&lt->bridge);
> +       lt8912_free_i2c(lt);
> +       lt8912_put_dt(lt);
> +
> +       return 0;
> +}
> +
> +static const struct of_device_id lt8912_dt_match[] = {
> +       {.compatible = "lontium,lt8912"},
> +       {}
> +};
> +MODULE_DEVICE_TABLE(of, lt8912_dt_match);
> +
> +static const struct i2c_device_id lt8912_id[] = {
> +       {"lt8912", 0},
> +       {},
> +};
> +MODULE_DEVICE_TABLE(i2c, lt8912_id);
> +
> +static struct i2c_driver lt8912_i2c_driver = {
> +       .driver = {
> +               .name = "lt8912",
> +               .of_match_table = lt8912_dt_match,
> +               .owner = THIS_MODULE,
> +       },
> +       .probe = lt8912_probe,
> +       .remove = lt8912_remove,
> +       .id_table = lt8912_id,
> +};
> +module_i2c_driver(lt8912_i2c_driver);
> +
> +MODULE_AUTHOR("Adrien Grassein <adrien.grassein@gmail.com>");
> +MODULE_DESCRIPTION("lt8912 drm driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.25.1
>