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Date: Fri, 16 Feb 2024 09:00:32 -0500
From: Hamza Mahfooz <hamza.mahfooz@....com>
To: Pekka Paalanen <pekka.paalanen@...oniitty.fi>
Cc: amd-gfx@...ts.freedesktop.org,
Mario Limonciello <mario.limonciello@....com>,
Harry Wentland <harry.wentland@....com>, Leo Li <sunpeng.li@....com>,
Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>,
"Pan, Xinhui" <Xinhui.Pan@....com>, David Airlie <airlied@...il.com>,
Daniel Vetter <daniel@...ll.ch>, Alex Hung <alex.hung@....com>,
Srinivasan Shanmugam <srinivasan.shanmugam@....com>,
Wayne Lin <wayne.lin@....com>, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/amd/display: add panel_power_savings sysfs entry
to eDP connectors
On 2/16/24 03:19, Pekka Paalanen wrote:
> On Fri, 2 Feb 2024 10:28:35 -0500
> Hamza Mahfooz <hamza.mahfooz@....com> wrote:
>
>> We want programs besides the compositor to be able to enable or disable
>> panel power saving features.
>
> Could you also explain why, in the commit message, please?
>
> It is unexpected for arbitrary programs to be able to override the KMS
> client, and certainly new ways to do so should not be added without an
> excellent justification.
Also, to be completely honest with you, I'm not sure why it was
initially exposed as a DRM prop, since it's a power management feature.
Which is to say, that it doesn't really make sense to have the
compositor control it.
>
> Maybe debugfs would be more appropriate if the purpose is only testing
> rather than production environments?
>
>> 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.
>
> When the DRM property was added, what was used as the userspace to
> prove its workings?
>
>
> Thanks,
> pq
>
>>
>> Cc: Mario Limonciello <mario.limonciello@....com>
>> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@....com>
>> ---
>> v2: hide ABM_LEVEL_IMMEDIATE_DISABLE in the read case, force an atomic
>> commit when setting the value, call sysfs_remove_group() in
>> amdgpu_dm_connector_unregister() and add some documentation.
>> ---
>> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 76 +++++++++++++++++++
>> 1 file changed, 76 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 8590c9f1dda6..3c62489d03dc 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -6436,10 +6436,79 @@ int amdgpu_dm_connector_atomic_get_property(struct drm_connector *connector,
>> return ret;
>> }
>>
>> +/**
>> + * DOC: panel power savings
>> + *
>> + * The display manager allows you to set your desired **panel power savings**
>> + * level (between 0-4, with 0 representing off), e.g. using the following::
>> + *
>> + * # echo 3 > /sys/class/drm/card0-eDP-1/amdgpu/panel_power_savings
>> + *
>> + * Modifying this value can have implications on color accuracy, so tread
>> + * carefully.
>> + */
>> +
>> +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;
>> + u8 val;
>> +
>> + drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
>> + val = to_dm_connector_state(connector->state)->abm_level ==
>> + ABM_LEVEL_IMMEDIATE_DISABLE ? 0 :
>> + to_dm_connector_state(connector->state)->abm_level;
>> + drm_modeset_unlock(&dev->mode_config.connection_mutex);
>> +
>> + return sysfs_emit(buf, "%u\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);
>> +
>> + drm_kms_helper_hotplug_event(dev);
>> +
>> + return count;
>> +}
>> +
>> +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 void amdgpu_dm_connector_unregister(struct drm_connector *connector)
>> {
>> struct amdgpu_dm_connector *amdgpu_dm_connector = to_amdgpu_dm_connector(connector);
>>
>> + sysfs_remove_group(&connector->kdev->kobj, &amdgpu_group);
>> drm_dp_aux_unregister(&amdgpu_dm_connector->dm_dp_aux.aux);
>> }
>>
>> @@ -6541,6 +6610,13 @@ 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;
>> + }
>> +
>> amdgpu_dm_register_backlight_device(amdgpu_dm_connector);
>>
>> if ((connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) ||
>
--
Hamza
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