[PATCH drm-dp 09/10] drm/hisilicon/hibmc: fix HPD no showing with VGA para of GRUB

[Yongbang Shi]

> On Fri, May 30, 2025 at 05:54:31PM +0800, Yongbang Shi wrote:
>> From: Baihan Li <libaihan at huawei.com>
>>
>> In early OS versions， there is a bug in hibmc-drm driver previously,
> Which OS? What does that mean? Why do we need to workaround userspace
> issues in the kernel?

We use OpenEuler 22.03, there is a VGA cfg(video=VGA-1:640x480-32 at 60me) in GRUB args.
If it exists, it will affect DP HPD.


>> so some OS add a VGA parameter in GRUB(video=VGA-1:640x480-32 at 60me) to
>> fix the bug, that will config a force VGA mode to drm driver. However, the
>> HPD problem exists that mentioned in previous patch, so change VGA's status
>> in force() to compatible with some older OS versions.
>>
>> Fixes: f9698f802e50 ("drm/hisilicon/hibmc: Restructuring the header dp_reg.h")
>> Signed-off-by: Baihan Li <libaihan at huawei.com>
>> ---
>>   drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c | 14 ++++++++++++++
>>   1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
>> index 73dd3d5fc26c..d609ccda2f2a 100644
>> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
>> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
>> @@ -61,6 +61,19 @@ static int hibmc_vdac_detect(struct drm_connector *connector, struct drm_modeset
>>   	return connector_status_connected;
>>   }
>>   
>> +static void hibmc_vdac_force(struct drm_connector *connector)
>> +{
>> +	struct hibmc_drm_private *priv = to_hibmc_drm_private(connector->dev);
>> +	struct hibmc_dp *dp = &priv->dp;
>> +
>> +	if (dp->hpd_status) {
>> +		connector->status = connector_status_disconnected;
>> +		return;
>> +	}
>> +
>> +	connector->status = connector_status_connected;
> You are again trying to tie VGA and DP status, so NAK.
>
>> +}
>> +
>>   static void hibmc_connector_destroy(struct drm_connector *connector)
>>   {
>>   	struct hibmc_vdac *vdac = to_hibmc_vdac(connector);
>> @@ -81,6 +94,7 @@ static const struct drm_connector_funcs hibmc_connector_funcs = {
>>   	.reset = drm_atomic_helper_connector_reset,
>>   	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
>>   	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
>> +	.force = hibmc_vdac_force,
>>   };
>>   
>>   static void hibmc_encoder_mode_set(struct drm_encoder *encoder,
>> -- 
>> 2.33.0
>>