Hello Michael,
Thank you for the patch. Sorry for the late reply, I wasn't on the CC
list so I didn't notice it.
On Fri, Aug 26, 2022 at 11:11:21AM +0200, Michael Rodin wrote:
> "detect" should not be called and its return value shall not be used when a
> connector is forced as hinted in the commit d50ba256b5f1 ("drm/kms: start
> adding command line interface using fb.") and the commit 6fe14acd496e
> ("drm: Document drm_connector_funcs"). One negative side effect of doing
> this is observed on the RCar3 SoCs which use the dw-hdmi driver. It
> continues executing drm_helper_hpd_irq_event even if its connector is
> forced to ON. As consequence drm_helper_hpd_irq_event calls "detect" so the
> connector status is updated to "disconnected":
>
> [ 420.201527] [drm:drm_helper_hpd_irq_event] [CONNECTOR:76:HDMI-A-1] status updated from connected to disconnected
>
> This status is corrected by drm_helper_probe_single_connector_modes shortly
> after this because this function checks if a connector is forced:
>
> [ 420.218703] [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:76:HDMI-A-1] status updated from disconnected to connected
>
> To avoid similar issues this commit adapts functions which call "detect"
> so they check if a connector is forced and return the correct status.
>
> Fixes: 949f08862d66 ("drm: Make the connector .detect() callback optional")
Is this really the right fixes tag ? The call to .detect() in
drm_helper_hpd_irq_event() predates that commit.
> Signed-off-by: Michael Rodin <mrodin@xxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_probe_helper.c | 16 ++++++++++++++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index bb427c5a4f1f..1691047d0472 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -289,7 +289,12 @@ drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
> retry:
> ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex, &ctx);
> if (!ret) {
> - if (funcs->detect_ctx)
> + if (connector->force == DRM_FORCE_ON ||
> + connector->force == DRM_FORCE_ON_DIGITAL)
> + ret = connector_status_connected;
> + else if (connector->force == DRM_FORCE_OFF)
> + ret = connector_status_disconnected;
> + else if (funcs->detect_ctx)
> ret = funcs->detect_ctx(connector, &ctx, force);
> else if (connector->funcs->detect)
> ret = connector->funcs->detect(connector, force);
> @@ -340,7 +345,14 @@ drm_helper_probe_detect(struct drm_connector *connector,
> if (ret)
> return ret;
>
> - if (funcs->detect_ctx)
> + if (connector->force == DRM_FORCE_ON ||
> + connector->force == DRM_FORCE_ON_DIGITAL)
> + ret = connector_status_connected;
> + else if (connector->force == DRM_FORCE_OFF)
> + ret = connector_status_disconnected;
> + else if (funcs->detect_ctx)
> + ret = funcs->detect_ctx(connector, ctx, force);
> + else if (funcs->detect_ctx)
> ret = funcs->detect_ctx(connector, ctx, force);
Those two conditions are identical.
> else if (connector->funcs->detect)
> ret = connector->funcs->detect(connector, force);
The same logic is used in two places in this patch. Could this be
factored out to a separate function ? It may even be possible to
refactor drm_helper_probe_detect() and drm_helper_probe_detect_ctx() to
share more code between the two functions.
This being said, I'm not sure this is the right fix. Beside the i915 and
nouveau drivers, the only callers of drm_helper_probe_detect() are
drm_helper_probe_single_connector_modes(), output_poll_execute() and
check_connector_changed() in this file. The first two functions already
check connector->force and skip the call to drm_helper_probe_detect() if
the connector is forced. Only check_connector_changed() is missing that
check. Wouldn't it be simpler to return false in that function if
connector->force is set ?
Another question is whether it is valid for the dw-hdmi driver to call
drm_helper_hpd_irq_event() when the connector status is forced.
Shouldn't HPD events be ignored in that case ?
The detection code has grown quite complex over time, I would really
appreciate input from Maxime and Maarten on this.
--
Regards,
Laurent Pinchart
