Re: [PATCH 10/10] drm/i915: Add privacy-screen support (v3)

[Hans de Goede <hdegoede@redhat.com>]

Hi Rajat,

On 11/17/21 14:59, Rajat Jain wrote:
> Hello Hans,
> 
> I'm working on my platform's privacy-screen support based on your
> patches, and had some (I know late) questions. Would be great if you
> could please help answer. Please see inline.
> 
> On Tue, Oct 5, 2021 at 1:25 PM Hans de Goede <hdegoede@redhat.com> wrote:
>>
>> Add support for eDP panels with a built-in privacy screen using the
>> new drm_privacy_screen class.
>>
>> Changes in v3:
>> - Move drm_privacy_screen_get() call to intel_ddi_init_dp_connector()
>>
>> Changes in v2:
>> - Call drm_connector_update_privacy_screen() from
>>   intel_enable_ddi_dp() / intel_ddi_update_pipe_dp() instead of adding a
>>   for_each_new_connector_in_state() loop to intel_atomic_commit_tail()
>> - Move the probe-deferral check to the intel_modeset_probe_defer() helper
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_atomic.c  |  1 +
>>  drivers/gpu/drm/i915/display/intel_ddi.c     | 16 ++++++++++++++++
>>  drivers/gpu/drm/i915/display/intel_display.c | 10 ++++++++++
>>  3 files changed, 27 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_atomic.c b/drivers/gpu/drm/i915/display/intel_atomic.c
>> index b4e7ac51aa31..a62550711e98 100644
>> --- a/drivers/gpu/drm/i915/display/intel_atomic.c
>> +++ b/drivers/gpu/drm/i915/display/intel_atomic.c
>> @@ -139,6 +139,7 @@ int intel_digital_connector_atomic_check(struct drm_connector *conn,
>>             new_conn_state->base.picture_aspect_ratio != old_conn_state->base.picture_aspect_ratio ||
>>             new_conn_state->base.content_type != old_conn_state->base.content_type ||
>>             new_conn_state->base.scaling_mode != old_conn_state->base.scaling_mode ||
>> +           new_conn_state->base.privacy_screen_sw_state != old_conn_state->base.privacy_screen_sw_state ||
>>             !drm_connector_atomic_hdr_metadata_equal(old_state, new_state))
>>                 crtc_state->mode_changed = true;
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
>> index 0d4cf7fa8720..272714e07cc6 100644
>> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
>> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
>> @@ -25,6 +25,7 @@
>>   *
>>   */
>>
>> +#include <drm/drm_privacy_screen_consumer.h>
>>  #include <drm/drm_scdc_helper.h>
>>
>>  #include "i915_drv.h"
>> @@ -2946,6 +2947,7 @@ static void intel_enable_ddi_dp(struct intel_atomic_state *state,
>>         if (port == PORT_A && DISPLAY_VER(dev_priv) < 9)
>>                 intel_dp_stop_link_train(intel_dp, crtc_state);
>>
>> +       drm_connector_update_privacy_screen(conn_state);
>>         intel_edp_backlight_on(crtc_state, conn_state);
>>
>>         if (!dig_port->lspcon.active || dig_port->dp.has_hdmi_sink)
>> @@ -3161,6 +3163,7 @@ static void intel_ddi_update_pipe_dp(struct intel_atomic_state *state,
>>         intel_drrs_update(intel_dp, crtc_state);
>>
>>         intel_backlight_update(state, encoder, crtc_state, conn_state);
>> +       drm_connector_update_privacy_screen(conn_state);
>>  }
>>
>>  void intel_ddi_update_pipe(struct intel_atomic_state *state,
>> @@ -3979,6 +3982,19 @@ intel_ddi_init_dp_connector(struct intel_digital_port *dig_port)
>>                 return NULL;
>>         }
>>
>> +       if (dig_port->base.type == INTEL_OUTPUT_EDP) {
>> +               struct drm_device *dev = dig_port->base.base.dev;
>> +               struct drm_privacy_screen *privacy_screen;
>> +
>> +               privacy_screen = drm_privacy_screen_get(dev->dev, NULL);
> 
> Why pass NULL for con_id? Can we pass something more meaningful (e.g.
> "eDP-1") so that the non-KMS platform components that provide the
> privacy-screen can provide a more specific lookup? Or is that
> information (connector name) not available at the time this call is
> being made?

For the x86 ACPI case it does not matter because the static lookups
added by drivers/gpu/drm/drm_privacy_screen_x86.c do not set
a con_id in the lookup and if the lookup lack a con_id then
the value passed to drm_privacy_screen_get() is a no-op.

So, if it helps you to pass a connector-name then go for it.

As for the connecter_name already being set at this point,
I don't know, you need to check.

But also see below.

>> +               if (!IS_ERR(privacy_screen)) {
>> +                       drm_connector_attach_privacy_screen_provider(&connector->base,
>> +                                                                    privacy_screen);
>> +               } else if (PTR_ERR(privacy_screen) != -ENODEV) {
>> +                       drm_warn(dev, "Error getting privacy-screen\n");
>> +               }
>> +       }
>> +
>>         return connector;
>>  }
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
>> index 86dbe366a907..84715a779d9d 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display.c
>> +++ b/drivers/gpu/drm/i915/display/intel_display.c
>> @@ -42,6 +42,7 @@
>>  #include <drm/drm_edid.h>
>>  #include <drm/drm_fourcc.h>
>>  #include <drm/drm_plane_helper.h>
>> +#include <drm/drm_privacy_screen_consumer.h>
>>  #include <drm/drm_probe_helper.h>
>>  #include <drm/drm_rect.h>
>>
>> @@ -12769,6 +12770,8 @@ void intel_modeset_driver_remove_nogem(struct drm_i915_private *i915)
>>
>>  bool intel_modeset_probe_defer(struct pci_dev *pdev)
>>  {
>> +       struct drm_privacy_screen *privacy_screen;
>> +
>>         /*
>>          * apple-gmux is needed on dual GPU MacBook Pro
>>          * to probe the panel if we're the inactive GPU.
>> @@ -12776,6 +12779,13 @@ bool intel_modeset_probe_defer(struct pci_dev *pdev)
>>         if (vga_switcheroo_client_probe_defer(pdev))
>>                 return true;
>>
>> +       /* If the LCD panel has a privacy-screen, wait for it */
>> +       privacy_screen = drm_privacy_screen_get(&pdev->dev, NULL);
>> +       if (IS_ERR(privacy_screen) && PTR_ERR(privacy_screen) == -EPROBE_DEFER)
>> +               return true;
>> +
>> +       drm_privacy_screen_put(privacy_screen);
>> +
>>         return false;
>>  }

So this is also going to be an interesting challenge for your device-tree (ish)
case. We cannot delay returning the -EPROBE_DEFER until the code in
intel_ddi_init_dp_connector() gets called because much of the i915 code is not
ready to deal with tearing down the house again once we are at that point (AFAIK).

For now I guess you/we could just hardcode "eDP-1" here. That is likely going
to be correct in all relevant cases (for now).

Regards,

Hans