Re: [PATCH] drm/amd/display: add panel_power_savings sysfs entry to eDP connectors

[Mario Limonciello]

On 1/26/2024 16:22, Hamza Mahfooz wrote:
> We want programs besides the compositor to be able to enable or disable
> panel power saving features. However, since they are currently only
> configurable through DRM properties, that isn't possible. So, to remedy
> that issue introduce a new "panel_power_savings" sysfs attribute.
>
> Cc: Mario Limonciello <mario.limonciello@xxxxxxx>
> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>
> ---
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 59 +++++++++++++++++++
>   1 file changed, 59 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index cd98b3565178..b3fcd833015d 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -6534,6 +6534,58 @@ amdgpu_dm_connector_atomic_duplicate_state(struct drm_connector *connector)
>   	return &new_state->base;
>   }
>   
> +static ssize_t panel_power_savings_show(struct device *device,
> +					struct device_attribute *attr,
> +					char *buf)
> +{
> +	struct drm_connector *connector = dev_get_drvdata(device);
> +	struct drm_device *dev = connector->dev;
> +	ssize_t val;
> +
> +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +	val = to_dm_connector_state(connector->state)->abm_level;
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +	return sysfs_emit(buf, "%lu\n", val);
> +}
> +
> +static ssize_t panel_power_savings_store(struct device *device,
> +					 struct device_attribute *attr,
> +					 const char *buf, size_t count)
> +{
> +	struct drm_connector *connector = dev_get_drvdata(device);
> +	struct drm_device *dev = connector->dev;
> +	long val;
> +	int ret;
> +
> +	ret = kstrtol(buf, 0, &val);
> +
> +	if (ret)
> +		return ret;
> +
> +	if (val < 0 || val > 4)
> +		return -EINVAL;
> +
> +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +	to_dm_connector_state(connector->state)->abm_level = val ?:
> +		ABM_LEVEL_IMMEDIATE_DISABLE;
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +	return count;
> +}
> +

To make this more discoverable I think you want some kerneldoc.

> +static DEVICE_ATTR_RW(panel_power_savings);
> +
> +static struct attribute *amdgpu_attrs[] = {
> +	&dev_attr_panel_power_savings.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group amdgpu_group = {
> +	.name = "amdgpu",
> +	.attrs = amdgpu_attrs
> +};
> +
>   static int
>   amdgpu_dm_connector_late_register(struct drm_connector *connector)
>   {
> @@ -6541,6 +6593,13 @@ amdgpu_dm_connector_late_register(struct drm_connector *connector)
>   		to_amdgpu_dm_connector(connector);
>   	int r;
>   
> +	if (connector->connector_type == DRM_MODE_CONNECTOR_eDP) {
> +		r = sysfs_create_group(&connector->kdev->kobj,
> +				       &amdgpu_group);
> +		if (r)
> +			return r;
> +	}
> +

I think there should be some matching code sysfs_remove_group(), maybe 
in early_unregister() callback.

>   	amdgpu_dm_register_backlight_device(amdgpu_dm_connector);
>   
>   	if ((connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) ||