Re: [PATCH v2 3/5] drm/ast: Support output polling

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 31 May 2022, Thomas Zimmermann <tzimmermann@suse.de> wrote:
> Enable output polling for all connectors. VGA always uses EDID for this. As
> there's currently no interrupt handling for the ast devices, we have to use
> that trick for the various DP and DVI ports as well.

In general, please don't add new helper functions under "drm/ast"
subject prefix. These will go under the radar. I only stumbled on this
by accident.

Please don't add new helper functions around get_modes and EDID
reading. I've been putting a lot of effort into changing how EDID will
be handled going forward, and this will just make it harder. See
e.g. [1], though there are pending review comments.

Please don't use connector->edid_blob_ptr for basically anything in the
drivers, or for logic regarding detection. It's way too overloaded
already, and difficult to untangle.


BR,
Jani.


[1] https://patchwork.freedesktop.org/series/104309/

>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>  drivers/gpu/drm/ast/ast_mode.c     | 14 ++++++++----
>  drivers/gpu/drm/drm_probe_helper.c | 35 ++++++++++++++++++++++++++++++
>  include/drm/drm_probe_helper.h     |  3 +++
>  3 files changed, 48 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
> index 4ff8ec1c8931..bbc566c4c768 100644
> --- a/drivers/gpu/drm/ast/ast_mode.c
> +++ b/drivers/gpu/drm/ast/ast_mode.c
> @@ -1319,6 +1319,7 @@ static int ast_vga_connector_helper_get_modes(struct drm_connector *connector)
>  
>  static const struct drm_connector_helper_funcs ast_vga_connector_helper_funcs = {
>  	.get_modes = ast_vga_connector_helper_get_modes,
> +	.detect_ctx = drm_connector_helper_detect_ctx_from_edid,
>  };
>  
>  static const struct drm_connector_funcs ast_vga_connector_funcs = {
> @@ -1354,7 +1355,7 @@ static int ast_vga_connector_init(struct drm_device *dev,
>  	connector->interlace_allowed = 0;
>  	connector->doublescan_allowed = 0;
>  
> -	connector->polled = DRM_CONNECTOR_POLL_CONNECT;
> +	connector->polled = DRM_CONNECTOR_POLL_CONNECT | DRM_CONNECTOR_POLL_DISCONNECT;
>  
>  	return 0;
>  }
> @@ -1390,6 +1391,7 @@ static int ast_vga_output_init(struct ast_private *ast)
>  
>  static const struct drm_connector_helper_funcs ast_sil164_connector_helper_funcs = {
>  	.get_modes = ast_vga_connector_helper_get_modes, // same as VGA connector
> +	.detect_ctx = drm_connector_helper_detect_ctx_from_edid,
>  };
>  
>  static const struct drm_connector_funcs ast_sil164_connector_funcs = {
> @@ -1425,7 +1427,7 @@ static int ast_sil164_connector_init(struct drm_device *dev,
>  	connector->interlace_allowed = 0;
>  	connector->doublescan_allowed = 0;
>  
> -	connector->polled = DRM_CONNECTOR_POLL_CONNECT;
> +	connector->polled = DRM_CONNECTOR_POLL_CONNECT | DRM_CONNECTOR_POLL_DISCONNECT;
>  
>  	return 0;
>  }
> @@ -1488,6 +1490,7 @@ static int ast_dp501_connector_helper_get_modes(struct drm_connector *connector)
>  
>  static const struct drm_connector_helper_funcs ast_dp501_connector_helper_funcs = {
>  	.get_modes = ast_dp501_connector_helper_get_modes,
> +	.detect_ctx = drm_connector_helper_detect_ctx_from_edid,
>  };
>  
>  static const struct drm_connector_funcs ast_dp501_connector_funcs = {
> @@ -1512,7 +1515,7 @@ static int ast_dp501_connector_init(struct drm_device *dev, struct drm_connector
>  	connector->interlace_allowed = 0;
>  	connector->doublescan_allowed = 0;
>  
> -	connector->polled = DRM_CONNECTOR_POLL_CONNECT;
> +	connector->polled = DRM_CONNECTOR_POLL_CONNECT | DRM_CONNECTOR_POLL_DISCONNECT;
>  
>  	return 0;
>  }
> @@ -1575,6 +1578,7 @@ static int ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
>  
>  static const struct drm_connector_helper_funcs ast_astdp_connector_helper_funcs = {
>  	.get_modes = ast_astdp_connector_helper_get_modes,
> +	.detect_ctx = drm_connector_helper_detect_ctx_from_edid,
>  };
>  
>  static const struct drm_connector_funcs ast_astdp_connector_funcs = {
> @@ -1599,7 +1603,7 @@ static int ast_astdp_connector_init(struct drm_device *dev, struct drm_connector
>  	connector->interlace_allowed = 0;
>  	connector->doublescan_allowed = 0;
>  
> -	connector->polled = DRM_CONNECTOR_POLL_CONNECT;
> +	connector->polled = DRM_CONNECTOR_POLL_CONNECT | DRM_CONNECTOR_POLL_DISCONNECT;
>  
>  	return 0;
>  }
> @@ -1709,5 +1713,7 @@ int ast_mode_config_init(struct ast_private *ast)
>  
>  	drm_mode_config_reset(dev);
>  
> +	drm_kms_helper_poll_init(dev);
> +
>  	return 0;
>  }
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index 425f56280d51..4440a7b6b240 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -1031,3 +1031,38 @@ int drm_connector_helper_get_modes_from_ddc(struct drm_connector *connector)
>  	return count;
>  }
>  EXPORT_SYMBOL(drm_connector_helper_get_modes_from_ddc);
> +
> +/**
> + * drm_connector_helper_detect_ctx_from_edid -
> + *	Updates the connector's status by reading EDID data
> + * @connector: The connector.
> + * @ctx: The lock-acquisition context.
> + * @force: True if the operation was requested by userspace, false otherwise.
> + *
> + * Returns:
> + * The connector's status as enum drm_connector_status.
> + *
> + * Updates the connector's EDID property by reading the display modes
> + * and returns the connector's status. If the EDID property is set, the
> + * connector is assumed to be connected; and disconnected otherwise.
> + * If the get_modes helper is missing, the default status is 'unknown'.
> + *
> + * See struct drm_connector_helper_funcs.detect_ctx.
> + */
> +int drm_connector_helper_detect_ctx_from_edid(struct drm_connector *connector,
> +					      struct drm_modeset_acquire_ctx *ctx,
> +					      bool force)
> +{
> +	const struct drm_connector_helper_funcs *helper_funcs = connector->helper_private;
> +
> +	if (!helper_funcs || !helper_funcs->get_modes)
> +		return connector_status_unknown;
> +
> +	helper_funcs->get_modes(connector);
> +
> +	if (!connector->edid_blob_ptr)
> +		return connector_status_disconnected;
> +
> +	return connector_status_connected;
> +}
> +EXPORT_SYMBOL(drm_connector_helper_detect_ctx_from_edid);
> diff --git a/include/drm/drm_probe_helper.h b/include/drm/drm_probe_helper.h
> index c80cab7a53b7..7408cf010794 100644
> --- a/include/drm/drm_probe_helper.h
> +++ b/include/drm/drm_probe_helper.h
> @@ -27,5 +27,8 @@ void drm_kms_helper_poll_enable(struct drm_device *dev);
>  bool drm_kms_helper_is_poll_worker(void);
>  
>  int drm_connector_helper_get_modes_from_ddc(struct drm_connector *connector);
> +int drm_connector_helper_detect_ctx_from_edid(struct drm_connector *connector,
> +					      struct drm_modeset_acquire_ctx *ctx,
> +					      bool force);
>  
>  #endif

-- 
Jani Nikula, Intel Open Source Graphics Center