Re: [PATCH 4/5] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

[Enric Balletbo Serra <eballetbo@gmail.com>]

Hi Peter,

Just some comments that I received when I submitted my bridge patches
and that I think can help you ...

2016-05-30 18:39 GMT+02:00 Peter Senna Tschudin <peter.senna@collabora.com>:
> This driver creates a drm_bridge and a drm_connector for the LVDS to DP++
> display bridge of the GE B850v3(imx6q-b850v3.dts). There are two physical
> bridges on the video signal pipeline: a STDP4028(LVDS to DP) and a
> STDP2690(DP to DP++). However the physical bridges are automatically
> configured by the input video signal, and the driver has no access to
> the video processing pipeline. The driver is only needed to read EDID
> from the STDP2690 and to handle HPD events from the STDP4028. The driver
> communicates with both bridges over i2c. The video signal pipeline is as
> follows:
>
>   Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output
>
> Signed-off-by: Peter Senna Tschudin <peter.senna@collabora.com>
> ---
>  MAINTAINERS                                |   8 +
>  drivers/gpu/drm/bridge/Kconfig             |   8 +
>  drivers/gpu/drm/bridge/Makefile            |   1 +
>  drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c | 397 +++++++++++++++++++++++++++++
>  4 files changed, 414 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 3273ffa..7bb5e89 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5009,6 +5009,14 @@ W:       https://linuxtv.org
>  S:     Maintained
>  F:     drivers/media/radio/radio-gemtek*
>
> +GENERAL ELECTRIC B850V3 LVDS/DP++ BRIDGE
> +M:     Martin Donnelly <martin.donnelly@ge.com>
> +M:     Peter Senna Tschudin <peter.senna@collabora.com>
> +M:     Martyn Welch <martyn.welch@collabora.co.uk>
> +S:     Maintained
> +F:     drivers/gpu/drm/bridge/ge_b850v3_dp2.c
> +F:     Documentation/devicetree/bindings/ge/b850v3_dp2_bridge.txt
> +
>  GENERIC GPIO I2C DRIVER
>  M:     Haavard Skinnemoen <hskinnemoen@gmail.com>
>  S:     Supported
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index 8f7423f..e9c32fc 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -52,4 +52,12 @@ config DRM_PARADE_PS8622
>
>  source "drivers/gpu/drm/bridge/analogix/Kconfig"
>
> +config DRM_GE_B850V3_LVDS_DP
> +       tristate "LVDS/DP bridge"
> +       depends on OF
> +       select DRM_KMS_HELPER
> +       select DRM_PANEL
> +       ---help---
> +         Driver for GE B850v3 DP2 LVDS to DP+ Bridge
> +

I think the maintainer prefers the entries ordered alphabetically (by
vendor, then name), so your config should go before "config
DRM_NXP_PTN3460"

>  endmenu
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 96b13b3..ba2e355 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -6,3 +6,4 @@ obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
>  obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
>  obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
>  obj-$(CONFIG_DRM_ANALOGIX_DP) += analogix/
> +obj-$(CONFIG_DRM_GE_B850V3_LVDS_DP) += ge_b850v3_lvds_dp.o

Same here,  this needs to be sorted by vendor, then name as well. Also
I think is preferred use hyphens like the others drivers.

Hmm, I see now that CONFIG_DRM_ANALOGIX_DP is not sorted, but I guess
the preferred is be sorted.

> diff --git a/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
> new file mode 100644
> index 0000000..37a4e7a
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
> @@ -0,0 +1,397 @@
> +/*
> + * Driver for GE B850v3 DP display bridge
> +
> + * Copyright (c) 2016, Collabora Ltd.
> + * Copyright (c) 2016, General Electric Company
> +
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> +
> + * This program is distributed in the hope 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.
> +
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> + * This driver creates a drm_bridge and a drm_connector for the LVDS to DP++
> + * display bridge of the GE B850v3. There are two physical bridges on the video
> + * signal pipeline: a STDP4028(LVDS to DP) and a STDP2690(DP to DP++). However
> + * the physical bridges are automatically configured by the input video signal,
> + * and the driver has no access to the video processing pipeline. The driver is
> + * only needed to read EDID from the STDP2690 and to handle HPD events from the
> + * STDP4028. The driver communicates with both bridges over i2c. The video
> + * signal pipeline is as follows:
> + *
> + *   Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output
> +
> + *
> + */
> +#include <linux/gpio.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include "drm_crtc.h"
> +#include "drm_crtc_helper.h"
> +#include "drm_edid.h"
> +#include "drmP.h"
> +
> +#define EDID_EXT_BLOCK_CNT 0x7E
> +
> +#define STDP4028_IRQ_OUT_CONF_REG 0x02
> +#define STDP4028_DPTX_IRQ_EN_REG 0x3C
> +#define STDP4028_DPTX_IRQ_STS_REG 0x3D
> +#define STDP4028_DPTX_STS_REG 0x3E
> +
> +#define STDP4028_DPTX_DP_IRQ_EN 0x1000
> +
> +#define STDP4028_DPTX_HOTPLUG_IRQ_EN 0x0400
> +#define STDP4028_DPTX_LINK_CH_IRQ_EN 0x2000
> +#define STDP4028_DPTX_IRQ_CONFIG \
> +               (STDP4028_DPTX_LINK_CH_IRQ_EN | STDP4028_DPTX_HOTPLUG_IRQ_EN)
> +
> +#define STDP4028_DPTX_HOTPLUG_STS 0x0200
> +#define STDP4028_DPTX_LINK_STS 0x1000
> +#define STDP4028_CON_STATE_CONNECTED \
> +               (STDP4028_DPTX_HOTPLUG_STS | STDP4028_DPTX_LINK_STS)
> +
> +#define STDP4028_DPTX_HOTPLUG_CH_STS 0x0400
> +#define STDP4028_DPTX_LINK_CH_STS 0x2000
> +#define STDP4028_DPTX_IRQ_CLEAR \
> +               (STDP4028_DPTX_LINK_CH_STS | STDP4028_DPTX_HOTPLUG_CH_STS)
> +
> +struct ge_b850v3_lvds_dp {
> +       struct drm_connector connector;
> +       struct drm_bridge bridge;
> +       struct i2c_client *ge_b850v3_lvds_dp_i2c;
> +       struct i2c_client *edid_i2c;
> +       struct edid *edid;
> +};
> +
> +static inline struct ge_b850v3_lvds_dp *
> +               bridge_to_ge_b850v3_lvds_dp(struct drm_bridge *bridge)
> +{
> +       return container_of(bridge, struct ge_b850v3_lvds_dp, bridge);
> +}
> +
> +static inline struct ge_b850v3_lvds_dp *
> +               connector_to_ge_b850v3_lvds_dp(struct drm_connector *connector)
> +{
> +       return container_of(connector, struct ge_b850v3_lvds_dp, connector);
> +}
> +
> +static void ge_b850v3_lvds_dp_pre_enable(struct drm_bridge *bridge)
> +{
> +}
> +

You don't need to keep empty callbacks for the (pre/post)
enable/disable drm_bridge ops anymore so you can remove this function
and the below.

> +static void ge_b850v3_lvds_dp_enable(struct drm_bridge *bridge)
> +{
> +}
> +
> +static void ge_b850v3_lvds_dp_disable(struct drm_bridge *bridge)
> +{
> +}
> +
> +static void ge_b850v3_lvds_dp_post_disable(struct drm_bridge *bridge)
> +{
> +}
> +
> +u8 *stdp2690_get_edid(struct i2c_client *client)
> +{
> +       struct i2c_adapter *adapter = client->adapter;
> +       unsigned char start = 0x00;
> +       unsigned int total_size;
> +       u8 *block = kmalloc(EDID_LENGTH, GFP_KERNEL);
> +
> +       struct i2c_msg msgs[] = {
> +               {
> +                       .addr   = client->addr,
> +                       .flags  = 0,
> +                       .len    = 1,
> +                       .buf    = &start,
> +               }, {
> +                       .addr   = client->addr,
> +                       .flags  = I2C_M_RD,
> +                       .len    = EDID_LENGTH,
> +                       .buf    = block,
> +               }
> +       };
> +
> +       if (!block)
> +               return NULL;
> +
> +       if (i2c_transfer(adapter, msgs, 2) != 2) {
> +               DRM_ERROR("Unable to read EDID.\n");
> +               goto err;
> +       }
> +
> +       if (!drm_edid_block_valid(block, 0, false, NULL)) {
> +               DRM_ERROR("Invalid EDID block\n");
> +               goto err;
> +       }
> +
> +       total_size = (block[EDID_EXT_BLOCK_CNT] + 1) * EDID_LENGTH;
> +       if (total_size > EDID_LENGTH) {
> +               kfree(block);
> +               block = kmalloc(total_size, GFP_KERNEL);
> +               if (!block)
> +                       return NULL;
> +
> +               /* Yes, read the entire buffer, and do not skip the first
> +                * EDID_LENGTH bytes.
> +                */
> +               start = 0x00;
> +               msgs[1].len = total_size;
> +               msgs[1].buf = block;
> +
> +               if (i2c_transfer(adapter, msgs, 2) != 2) {
> +                       DRM_ERROR("Unable to read EDID extension blocks.\n");
> +                       goto err;
> +               }
> +       }
> +
> +       return block;
> +
> +err:
> +       kfree(block);
> +       return NULL;
> +}
> +
> +static int ge_b850v3_lvds_dp_get_modes(struct drm_connector *connector)
> +{
> +       struct ge_b850v3_lvds_dp *ptn_bridge;
> +       struct i2c_client *client;
> +       u8 *block;
> +       int num_modes;
> +
> +       ptn_bridge = connector_to_ge_b850v3_lvds_dp(connector);

Move this assignation to ptn_bridge declaration

> +       client = ptn_bridge->edid_i2c;
> +
> +       block = stdp2690_get_edid(client);

I think you can remove the client variable and pass
ptn_bridge->edid_i2c directly to the stdp2690_get_edid function.

Note that get_modes is called several times and can be called from
userspace, you are allocating memory on every call to get_modes that I
think is not released or I'm missing something?

> +       ptn_bridge->edid = (struct edid *) block;
> +

What if block is NULL here ?

> +       drm_mode_connector_update_edid_property(connector, ptn_bridge->edid);
> +       num_modes = drm_add_edid_modes(connector, ptn_bridge->edid);
> +
> +       return num_modes;

nit: return drm_add_edid_modes(connector, ptn_bridge->edid); ? And
remove num_modes ?

> +}
> +
> +static struct drm_encoder
> +*ge_b850v3_lvds_dp_best_encoder(struct drm_connector *connector)
> +{
> +       struct ge_b850v3_lvds_dp *ptn_bridge =
> +               connector_to_ge_b850v3_lvds_dp(connector);
> +
> +       return ptn_bridge->bridge.encoder;
> +}
> +
> +static const struct
> +drm_connector_helper_funcs ge_b850v3_lvds_dp_connector_helper_funcs = {
> +       .get_modes = ge_b850v3_lvds_dp_get_modes,
> +       .best_encoder = ge_b850v3_lvds_dp_best_encoder,
> +};
> +
> +static enum drm_connector_status ge_b850v3_lvds_dp_detect(
> +               struct drm_connector *connector, bool force)
> +{
> +       struct ge_b850v3_lvds_dp *ptn_bridge =
> +                       connector_to_ge_b850v3_lvds_dp(connector);
> +       struct i2c_client *ge_b850v3_lvds_dp_i2c =
> +                       ptn_bridge->ge_b850v3_lvds_dp_i2c;
> +       s32 link_state;
> +
> +       link_state = i2c_smbus_read_word_data(ge_b850v3_lvds_dp_i2c,
> +                       STDP4028_DPTX_STS_REG);
> +
> +       if (link_state == STDP4028_CON_STATE_CONNECTED)
> +               return connector_status_connected;
> +
> +       if (link_state == 0)
> +               return connector_status_disconnected;
> +
> +       return connector_status_unknown;
> +}
> +
> +static void ge_b850v3_lvds_dp_connector_force(struct drm_connector *connector)
> +{
> +}
> +

Guess you can remove this empty callback.

> +static void ge_b850v3_lvds_dp_connector_destroy(struct drm_connector *connector)
> +{
> +       drm_connector_cleanup(connector);
> +}
> +
> +static const struct drm_connector_funcs ge_b850v3_lvds_dp_connector_funcs = {
> +       .dpms = drm_helper_connector_dpms,
> +       .fill_modes = drm_helper_probe_single_connector_modes,
> +       .detect = ge_b850v3_lvds_dp_detect,
> +       .destroy = ge_b850v3_lvds_dp_connector_destroy,
> +       .force = ge_b850v3_lvds_dp_connector_force,

Remove .force

> +};
> +
> +static irqreturn_t ge_b850v3_lvds_dp_irq_handler(int irq, void *dev_id)
> +{
> +       struct ge_b850v3_lvds_dp *ptn_bridge = dev_id;
> +       struct i2c_client *ge_b850v3_lvds_dp_i2c
> +                       = ptn_bridge->ge_b850v3_lvds_dp_i2c;
> +
> +       i2c_smbus_write_word_data(ge_b850v3_lvds_dp_i2c,
> +                       STDP4028_DPTX_IRQ_STS_REG, STDP4028_DPTX_IRQ_CLEAR);
> +
> +       if (ptn_bridge->connector.dev)
> +               drm_kms_helper_hotplug_event(ptn_bridge->connector.dev);
> +
> +       return IRQ_HANDLED;
> +

Remove the empty line.

> +}
> +
> +static int ge_b850v3_lvds_dp_attach(struct drm_bridge *bridge)
> +{
> +       struct ge_b850v3_lvds_dp *ptn_bridge
> +                       = bridge_to_ge_b850v3_lvds_dp(bridge);
> +       struct drm_connector *connector = &ptn_bridge->connector;
> +       struct i2c_client *ge_b850v3_lvds_dp_i2c
> +                       = ptn_bridge->ge_b850v3_lvds_dp_i2c;
> +       int ret;
> +
> +       if (!bridge->encoder) {
> +               DRM_ERROR("Parent encoder object not found");
> +               return -ENODEV;
> +       }
> +
> +       connector->polled = DRM_CONNECTOR_POLL_HPD;
> +
> +       drm_connector_helper_add(connector,
> +                       &ge_b850v3_lvds_dp_connector_helper_funcs);
> +
> +       ret = drm_connector_init(bridge->dev, connector,
> +                       &ge_b850v3_lvds_dp_connector_funcs,
> +                       DRM_MODE_CONNECTOR_DisplayPort);
> +       if (ret) {
> +               DRM_ERROR("Failed to initialize connector with drm\n");
> +               return ret;
> +       }
> +
> +       ret = drm_mode_connector_attach_encoder(connector, bridge->encoder);
> +       if (ret)
> +               return ret;
> +
> +       drm_bridge_enable(bridge);
> +       if (ge_b850v3_lvds_dp_i2c->irq) {
> +               drm_helper_hpd_irq_event(connector->dev);
> +
> +               ret = devm_request_threaded_irq(&ge_b850v3_lvds_dp_i2c->dev,
> +                               ge_b850v3_lvds_dp_i2c->irq, NULL,
> +                               ge_b850v3_lvds_dp_irq_handler,
> +                               IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
> +                               "ge_b850v3_lvds_dp", ptn_bridge);
> +               if (ret)
> +                       return ret;
> +       }
> +
> +       return 0;
> +}
> +
> +static const struct drm_bridge_funcs ge_b850v3_lvds_dp_funcs = {
> +       .pre_enable = ge_b850v3_lvds_dp_pre_enable,
> +       .enable = ge_b850v3_lvds_dp_enable,
> +       .disable = ge_b850v3_lvds_dp_disable,
> +       .post_disable = ge_b850v3_lvds_dp_post_disable,

Remove the above empty callbacks.

> +       .attach = ge_b850v3_lvds_dp_attach,
> +};
> +
> +static int ge_b850v3_lvds_dp_probe(struct i2c_client *ge_b850v3_lvds_dp_i2c,
> +                               const struct i2c_device_id *id)
> +{
> +       struct device *dev = &ge_b850v3_lvds_dp_i2c->dev;
> +       struct ge_b850v3_lvds_dp *ptn_bridge;
> +

Remove this empty line between these two blocks.

> +       int ret;
> +       u32 edid_i2c_reg;
> +
> +       ptn_bridge = devm_kzalloc(dev, sizeof(*ptn_bridge), GFP_KERNEL);
> +       if (!ptn_bridge)
> +               return -ENOMEM;
> +
> +       ptn_bridge->ge_b850v3_lvds_dp_i2c = ge_b850v3_lvds_dp_i2c;
> +       ptn_bridge->bridge.driver_private = ptn_bridge;
> +       i2c_set_clientdata(ge_b850v3_lvds_dp_i2c, ptn_bridge);
> +
> +       ret = of_property_read_u32(dev->of_node, "edid-reg", &edid_i2c_reg);
> +       if (ret) {
> +               dev_err(dev, "edid-reg not specified, aborting...\n");

Use DRM_ERROR?

> +               return -ENODEV;
> +       }
> +
> +       ptn_bridge->edid_i2c = devm_kzalloc(dev,
> +                       sizeof(struct i2c_client), GFP_KERNEL);
> +
> +       if (!ptn_bridge->edid_i2c)
> +               return -ENOMEM;
> +
> +       memcpy(ptn_bridge->edid_i2c, ge_b850v3_lvds_dp_i2c,
> +                       sizeof(struct i2c_client));
> +
> +       ptn_bridge->edid_i2c->addr = (unsigned short) edid_i2c_reg;
> +

Remove empty line.

> +
> +       /* Configures the bridge to re-enable interrupts after each ack */
> +       i2c_smbus_write_word_data(ge_b850v3_lvds_dp_i2c,
> +                       STDP4028_IRQ_OUT_CONF_REG, STDP4028_DPTX_DP_IRQ_EN);
> +       i2c_smbus_write_word_data(ge_b850v3_lvds_dp_i2c,
> +                       STDP4028_DPTX_IRQ_EN_REG, STDP4028_DPTX_IRQ_CONFIG);
> +
> +       /* Clear pending interrupts since power up. */
> +       i2c_smbus_write_word_data(ge_b850v3_lvds_dp_i2c,
> +                       STDP4028_DPTX_IRQ_STS_REG, STDP4028_DPTX_IRQ_CLEAR);
> +
> +       ptn_bridge->bridge.funcs = &ge_b850v3_lvds_dp_funcs;
> +       ptn_bridge->bridge.of_node = dev->of_node;
> +       ret = drm_bridge_add(&ptn_bridge->bridge);
> +       if (ret) {
> +               DRM_ERROR("Failed to add bridge\n");
> +               return ret;
> +       }
> +
> +       return 0;
> +}
> +
> +static int ge_b850v3_lvds_dp_remove(struct i2c_client *ge_b850v3_lvds_dp_i2c)
> +{
> +       struct ge_b850v3_lvds_dp *ptn_bridge =
> +               i2c_get_clientdata(ge_b850v3_lvds_dp_i2c);
> +
> +       drm_bridge_remove(&ptn_bridge->bridge);
> +
> +       return 0;
> +}
> +
> +static const struct i2c_device_id ge_b850v3_lvds_dp_i2c_table[] = {
> +       {"b850v3_lvds_dp", 0},
> +       {},
> +};
> +MODULE_DEVICE_TABLE(i2c, ge_b850v3_lvds_dp_i2c_table);
> +
> +static const struct of_device_id ge_b850v3_lvds_dp_match[] = {
> +       { .compatible = "ge,b850v3_lvds_dp" },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(of, ge_b850v3_lvds_dp_match);
> +
> +static struct i2c_driver ge_b850v3_lvds_dp_driver = {
> +       .id_table       = ge_b850v3_lvds_dp_i2c_table,
> +       .probe          = ge_b850v3_lvds_dp_probe,
> +       .remove         = ge_b850v3_lvds_dp_remove,
> +       .driver         = {
> +               .name           = "ge,b850v3_lvds_dp",
> +               .of_match_table = ge_b850v3_lvds_dp_match,
> +       },
> +};
> +module_i2c_driver(ge_b850v3_lvds_dp_driver);
> +
> +MODULE_AUTHOR("Peter Senna Tschudin <peter.senna@collabora.com>");
> +MODULE_AUTHOR("Martyn Welch <martyn.welch@collabora.co.uk>");
> +MODULE_DESCRIPTION("GE LVDS to DP++ bridge)");
> +MODULE_LICENSE("GPL v2");
> --
> 2.5.5
>

Best regards,
   Enric