Re: [Intel-gfx] [PATCH 9/9] drm/i915: Add privacy-screen support

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

Hi,

On 9/15/21 11:11 PM, Lyude Paul wrote:
> On Mon, 2021-09-06 at 09:35 +0200, Hans de Goede wrote:
>> Add support for eDP panels with a built-in privacy screen using the
>> new drm_privacy_screen class.
>>
>> One thing which stands out here is the addition of these 2 lines to
>> intel_atomic_commit_tail:
>>
>>         for_each_new_connector_in_state(&state->base, connector, ...
>>                 drm_connector_update_privacy_screen(connector, state);
>>
>> It may seem more logical to instead take care of updating the
>> privacy-screen state by marking the crtc as needing a modeset and then
>> do this in both the encoder update_pipe (for fast-sets) and enable
>> (for full modesets) callbacks. But ATM these callbacks only get passed
>> the new connector_state and these callbacks are all called after
>> drm_atomic_helper_swap_state() at which point there is no way to get
>> the old state from the new state.
> 
> I was going to suggest that you workaround this simply by adding a variable
> that corresponds to the most recently committed privacy screen state somewhere
> in a driver private structure. But, then I realized that's basically the same
> as what you're doing now except that your current solution stores said state
> in a shared struct. So, I think you probably do have the right idea here as
> long as we don't get any non-ACPI providers in the future. This also seems
> like something that wouldn't be difficult to fixup down the line if that ends
> up changing.

Ack, this is all kernel internal stuff so we can always rework it if necessary.

Regards,

Hans




> 
>>
>> Without access to the old state, we do not know if the sw_state of
>> the privacy-screen has changes so we would need to call
>> drm_privacy_screen_set_sw_state() unconditionally. This is undesirable
>> since all current known privacy-screen providers use ACPI calls which
>> are somewhat expensive to make.
>>
>> Also, as all providers use ACPI calls, rather then poking GPU registers,
>> there is no need to order this together with other encoder operations.
>> Since no GPU poking is involved having this as a separate step of the
>> commit process actually is the logical thing to do.
>>
>> Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_display.c |  5 +++++
>>  drivers/gpu/drm/i915/display/intel_dp.c      | 10 ++++++++++
>>  drivers/gpu/drm/i915/i915_pci.c              | 12 ++++++++++++
>>  3 files changed, 27 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_display.c
>> b/drivers/gpu/drm/i915/display/intel_display.c
>> index 5560d2f4c352..7285873d329a 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display.c
>> +++ b/drivers/gpu/drm/i915/display/intel_display.c
>> @@ -10140,6 +10140,8 @@ static void intel_atomic_commit_tail(struct
>> intel_atomic_state *state)
>>         struct drm_device *dev = state->base.dev;
>>         struct drm_i915_private *dev_priv = to_i915(dev);
>>         struct intel_crtc_state *new_crtc_state, *old_crtc_state;
>> +       struct drm_connector_state *new_connector_state;
>> +       struct drm_connector *connector;
>>         struct intel_crtc *crtc;
>>         u64 put_domains[I915_MAX_PIPES] = {};
>>         intel_wakeref_t wakeref = 0;
>> @@ -10237,6 +10239,9 @@ static void intel_atomic_commit_tail(struct
>> intel_atomic_state *state)
>>                         intel_color_load_luts(new_crtc_state);
>>         }
>>  
>> +       for_each_new_connector_in_state(&state->base, connector,
>> new_connector_state, i)
>> +               drm_connector_update_privacy_screen(connector, &state-
>>> base);
>> +
>>         /*
>>          * Now that the vblank has passed, we can go ahead and program the
>>          * optimal watermarks on platforms that need two-step watermark
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
>> b/drivers/gpu/drm/i915/display/intel_dp.c
>> index 7f8e8865048f..3aa2072cccf6 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -37,6 +37,7 @@
>>  #include <drm/drm_crtc.h>
>>  #include <drm/drm_dp_helper.h>
>>  #include <drm/drm_edid.h>
>> +#include <drm/drm_privacy_screen_consumer.h>
>>  #include <drm/drm_probe_helper.h>
>>  
>>  #include "g4x_dp.h"
>> @@ -5217,6 +5218,7 @@ static bool intel_edp_init_connector(struct intel_dp
>> *intel_dp,
>>         struct drm_connector *connector = &intel_connector->base;
>>         struct drm_display_mode *fixed_mode = NULL;
>>         struct drm_display_mode *downclock_mode = NULL;
>> +       struct drm_privacy_screen *privacy_screen;
>>         bool has_dpcd;
>>         enum pipe pipe = INVALID_PIPE;
>>         struct edid *edid;
>> @@ -5308,6 +5310,14 @@ static bool intel_edp_init_connector(struct intel_dp
>> *intel_dp,
>>                                 fixed_mode->hdisplay, fixed_mode->vdisplay);
>>         }
>>  
>> +       privacy_screen = drm_privacy_screen_get(dev->dev, NULL);
>> +       if (!IS_ERR(privacy_screen)) {
>> +               drm_connector_attach_privacy_screen_provider(connector,
>> +                                                           
>> privacy_screen);
>> +       } else if (PTR_ERR(privacy_screen) != -ENODEV) {
>> +               drm_warn(&dev_priv->drm, "Error getting privacy-screen\n");
>> +       }
>> +
>>         return true;
>>  
>>  out_vdd_off:
>> diff --git a/drivers/gpu/drm/i915/i915_pci.c
>> b/drivers/gpu/drm/i915/i915_pci.c
>> index 146f7e39182a..d6913f567a1c 100644
>> --- a/drivers/gpu/drm/i915/i915_pci.c
>> +++ b/drivers/gpu/drm/i915/i915_pci.c
>> @@ -25,6 +25,7 @@
>>  #include <linux/vga_switcheroo.h>
>>  
>>  #include <drm/drm_drv.h>
>> +#include <drm/drm_privacy_screen_consumer.h>
>>  #include <drm/i915_pciids.h>
>>  
>>  #include "i915_drv.h"
>> @@ -1167,6 +1168,7 @@ static int i915_pci_probe(struct pci_dev *pdev, const
>> struct pci_device_id *ent)
>>  {
>>         struct intel_device_info *intel_info =
>>                 (struct intel_device_info *) ent->driver_data;
>> +       struct drm_privacy_screen *privacy_screen;
>>         int err;
>>  
>>         if (intel_info->require_force_probe &&
>> @@ -1195,7 +1197,17 @@ static int i915_pci_probe(struct pci_dev *pdev, const
>> struct pci_device_id *ent)
>>         if (vga_switcheroo_client_probe_defer(pdev))
>>                 return -EPROBE_DEFER;
>>  
>> +       /*
>> +        * We do not handle -EPROBE_DEFER further into the probe process, so
>> +        * check if we have a laptop-panel privacy-screen for which the
>> driver
>> +        * has not loaded yet here.
>> +        */
>> +       privacy_screen = drm_privacy_screen_get(&pdev->dev, NULL);
>> +       if (IS_ERR(privacy_screen) && PTR_ERR(privacy_screen) == -
>> EPROBE_DEFER)
>> +               return -EPROBE_DEFER;
>> +
>>         err = i915_driver_probe(pdev, ent);
>> +       drm_privacy_screen_put(privacy_screen);
>>         if (err)
>>                 return err;
>>  
>