Re: [PATCH 2/2] drm/i915: Prevent HW access during init from connector get_modes hooks

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Tue, 2024-02-06 at 17:39 +0200, Imre Deak wrote:
> Prevent accessing the HW from the get_modes hooks of connectors
> deriving
> the mode list from the display's EDID. drm_edid_connector_add_modes()
> will return the mode list based on the EDID which was cached during a
> previous detection/get_modes call.
> 
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10085
> Signed-off-by: Imre Deak <imre.deak@intel.com>

Reviewed-by: Jouni Högander <jouni.hogander@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_crt.c    | 7 +++++++
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 4 ++++
>  drivers/gpu/drm/i915/display/intel_dvo.c    | 5 +++++
>  drivers/gpu/drm/i915/display/intel_sdvo.c   | 4 ++++
>  4 files changed, 20 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_crt.c
> b/drivers/gpu/drm/i915/display/intel_crt.c
> index b9733a73e21d4..27c5595e5d6bc 100644
> --- a/drivers/gpu/drm/i915/display/intel_crt.c
> +++ b/drivers/gpu/drm/i915/display/intel_crt.c
> @@ -646,9 +646,13 @@ static const struct drm_edid
> *intel_crt_get_edid(struct drm_connector *connector
>  static int intel_crt_ddc_get_modes(struct drm_connector *connector,
>                                    struct i2c_adapter *ddc)
>  {
> +       struct drm_i915_private *i915 = to_i915(connector->dev);
>         const struct drm_edid *drm_edid;
>         int ret;
>  
> +       if (!intel_display_driver_check_access(i915))
> +               return drm_edid_connector_add_modes(connector);
> +
>         drm_edid = intel_crt_get_edid(connector, ddc);
>         if (!drm_edid)
>                 return 0;
> @@ -933,6 +937,9 @@ static int intel_crt_get_modes(struct
> drm_connector *connector)
>         struct i2c_adapter *ddc;
>         int ret;
>  
> +       if (!intel_display_driver_check_access(dev_priv))
> +               return drm_edid_connector_add_modes(connector);
> +
>         wakeref = intel_display_power_get(dev_priv,
>                                           intel_encoder-
> >power_domain);
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 5fa25a5a36b55..5307ddd4edcf5 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -1197,6 +1197,7 @@ static bool
> intel_dp_mst_initial_fastset_check(struct intel_encoder *encoder,
>  static int intel_dp_mst_get_ddc_modes(struct drm_connector
> *connector)
>  {
>         struct intel_connector *intel_connector =
> to_intel_connector(connector);
> +       struct drm_i915_private *i915 = to_i915(intel_connector-
> >base.dev);
>         struct intel_dp *intel_dp = intel_connector->mst_port;
>         const struct drm_edid *drm_edid;
>         int ret;
> @@ -1204,6 +1205,9 @@ static int intel_dp_mst_get_ddc_modes(struct
> drm_connector *connector)
>         if (drm_connector_is_unregistered(connector))
>                 return intel_connector_update_modes(connector, NULL);
>  
> +       if (!intel_display_driver_check_access(i915))
> +               return drm_edid_connector_add_modes(connector);
> +
>         drm_edid = drm_dp_mst_edid_read(connector, &intel_dp-
> >mst_mgr, intel_connector->port);
>  
>         ret = intel_connector_update_modes(connector, drm_edid);
> diff --git a/drivers/gpu/drm/i915/display/intel_dvo.c
> b/drivers/gpu/drm/i915/display/intel_dvo.c
> index 8ca9ae4798a89..c076da75b066e 100644
> --- a/drivers/gpu/drm/i915/display/intel_dvo.c
> +++ b/drivers/gpu/drm/i915/display/intel_dvo.c
> @@ -30,6 +30,7 @@
>  
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_crtc.h>
> +#include <drm/drm_edid.h>
>  
>  #include "i915_drv.h"
>  #include "i915_reg.h"
> @@ -338,8 +339,12 @@ intel_dvo_detect(struct drm_connector
> *_connector, bool force)
>  static int intel_dvo_get_modes(struct drm_connector *_connector)
>  {
>         struct intel_connector *connector =
> to_intel_connector(_connector);
> +       struct drm_i915_private *i915 = to_i915(connector->base.dev);
>         int num_modes;
>  
> +       if (!intel_display_driver_check_access(i915))
> +               return drm_edid_connector_add_modes(&connector-
> >base);
> +
>         /*
>          * We should probably have an i2c driver get_modes function
> for those
>          * devices which will have a fixed set of modes determined by
> the chip
> diff --git a/drivers/gpu/drm/i915/display/intel_sdvo.c
> b/drivers/gpu/drm/i915/display/intel_sdvo.c
> index ccea0efbd136f..dae5abf56bbf5 100644
> --- a/drivers/gpu/drm/i915/display/intel_sdvo.c
> +++ b/drivers/gpu/drm/i915/display/intel_sdvo.c
> @@ -2189,12 +2189,16 @@ intel_sdvo_detect(struct drm_connector
> *connector, bool force)
>  
>  static int intel_sdvo_get_ddc_modes(struct drm_connector *connector)
>  {
> +       struct drm_i915_private *i915 = to_i915(connector->dev);
>         int num_modes = 0;
>         const struct drm_edid *drm_edid;
>  
>         DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
>                       connector->base.id, connector->name);
>  
> +       if (!intel_display_driver_check_access(i915))
> +               return drm_edid_connector_add_modes(connector);
> +
>         /* set the bus switch and get the modes */
>         drm_edid = intel_sdvo_get_edid(connector);
>