Re: [PATCH v3 drm-dp 08/11] drm/hisilicon/hibmc: fix no showing when no connectors connected

[Yongbang Shi <shiyongbang@huawei.com>]

> On Fri, Jul 18, 2025 at 02:51:22PM +0800, Yongbang Shi wrote:
>> From: Baihan Li <libaihan@huawei.com>
>>
>> Our chip support KVM over IP feature, so hibmc diiver need to support
> I assume that KVM-over-IP doesnt provide EDID reads. This needs to be
> stated in the commit message.

Okay!


>> displaying without any connectors plugged in. If no connectors connected,
>> set the vdac connector status to 'connected' to handle BMC KVM. Use
>> is_connected to check all physical outputs.
>> For get_modes: using BMC modes for connector if no display is attached to
>> phys VGA cable, otherwise use EDID modes by drm_connector_helper_get_modes.
>>
>> Fixes: 4c962bc929f1 ("drm/hisilicon/hibmc: Add vga connector detect functions")
>> Signed-off-by: Baihan Li <libaihan@huawei.com>
>> Signed-off-by: Yongbang Shi <shiyongbang@huawei.com>
>> ---
>> ChangeLog:
>> v2 -> v3:
>>    - fix hibmc_connector_get_modes() and hibmc_vdac_detect() to realize BMC KVM, suggested by Dmitry Baryshkov.
>> ---
>>   .../gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c    |  5 +-
>>   .../gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h   |  4 ++
>>   .../gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c  | 55 +++++++++++++------
>>   3 files changed, 45 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
>> index 99b30a6c7e06..262ebe6138f0 100644
>> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
>> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
>> @@ -58,9 +58,12 @@ static int hibmc_dp_detect(struct drm_connector *connector,
>>   {
>>   	struct hibmc_drm_private *priv = to_hibmc_drm_private(connector->dev);
>>   
>> -	if (!hibmc_dp_detect_link(&priv->dp))
>> +	if (!hibmc_dp_detect_link(&priv->dp)) {
>> +		priv->is_connected |= BIT(0);
> Magic value BIT(0)
>
>>   		return connector_status_connected;
>> +	}
>>   
>> +	priv->is_connected &= ~BIT(0);
>>   	return connector_status_disconnected;
>>   }
>>   
>> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h
>> index ca8502e2760c..d68588ecec9b 100644
>> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h
>> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h
>> @@ -31,6 +31,7 @@ struct hibmc_vdac {
>>   	struct drm_connector connector;
>>   	struct i2c_adapter adapter;
>>   	struct i2c_algo_bit_data bit_data;
>> +	int phys_status;
>>   };
>>   
>>   struct hibmc_drm_private {
>> @@ -43,6 +44,9 @@ struct hibmc_drm_private {
>>   	struct drm_crtc crtc;
>>   	struct hibmc_vdac vdac;
>>   	struct hibmc_dp dp;
>> +
>> +	/* VGA and DP phys connect status, BIT(0) is DP, BIT(1) is VGA */
> #define those.
>
>> +	int is_connected;
> And you need a lock around this one, otherwise you might get a race
> between DP's and VGA's code setting and clearing bits here.

Okay, thanks for your advice!
I will modify all of the above issues.


>>   };
>>   
>>   static inline struct hibmc_vdac *to_hibmc_vdac(struct drm_connector *connector)
>> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
>> index 841e81f47b68..3cdf640d1785 100644
>> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
>> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
>> @@ -25,27 +25,18 @@
>>   static int hibmc_connector_get_modes(struct drm_connector *connector)
>>   {
>>   	struct hibmc_vdac *vdac = to_hibmc_vdac(connector);
>> -	const struct drm_edid *drm_edid;
>>   	int count;
>>   
>> -	drm_edid = drm_edid_read_ddc(connector, &vdac->adapter);
>> -
>> -	drm_edid_connector_update(connector, drm_edid);
>> -
>> -	if (drm_edid) {
>> -		count = drm_edid_connector_add_modes(connector);
>> -		if (count)
>> -			goto out;
>> +	if (vdac->phys_status == connector_status_connected) {
>> +		count = drm_connector_helper_get_modes(connector);
>> +	} else {
>> +		drm_edid_connector_update(connector, NULL);
>> +		count = drm_add_modes_noedid(connector,
>> +					     connector->dev->mode_config.max_width,
>> +					     connector->dev->mode_config.max_height);
>> +		drm_set_preferred_mode(connector, 1024, 768); // 1024x768
>>   	}
>>   
>> -	count = drm_add_modes_noedid(connector,
>> -				     connector->dev->mode_config.max_width,
>> -				     connector->dev->mode_config.max_height);
>> -	drm_set_preferred_mode(connector, 1024, 768);
>> -
>> -out:
>> -	drm_edid_free(drm_edid);
>> -
>>   	return count;
>>   }
>>   
>> @@ -57,10 +48,38 @@ static void hibmc_connector_destroy(struct drm_connector *connector)
>>   	drm_connector_cleanup(connector);
>>   }
>>   
>> +static int hibmc_vdac_detect(struct drm_connector *connector,
>> +			     struct drm_modeset_acquire_ctx *ctx,
>> +			     bool force)
>> +{
>> +	struct hibmc_drm_private *priv = to_hibmc_drm_private(connector->dev);
>> +	struct hibmc_vdac *vdac = to_hibmc_vdac(connector);
>> +	enum drm_connector_status status;
>> +
>> +	status = drm_connector_helper_detect_from_ddc(connector, ctx, force);
>> +
>> +	vdac->phys_status = status;
>> +
>> +	if (status == connector_status_connected) {
>> +		priv->is_connected |= BIT(1);
>> +		return connector_status_connected;
>> +	}
>> +
>> +	priv->is_connected &= ~BIT(1);
>> +
>> +	/* if all connectors are disconnected,
>> +	 * return connected to support BMC KVM display.
>> +	 */
>> +	if (!priv->is_connected)
>> +		return connector_status_connected;
>> +
>> +	return connector_status_disconnected;
>> +}
>> +
>>   static const struct drm_connector_helper_funcs
>>   	hibmc_connector_helper_funcs = {
>>   	.get_modes = hibmc_connector_get_modes,
>> -	.detect_ctx = drm_connector_helper_detect_from_ddc,
>> +	.detect_ctx = hibmc_vdac_detect,
>>   };
>>   
>>   static const struct drm_connector_funcs hibmc_connector_funcs = {
>> -- 
>> 2.33.0
>>