On Tue, Apr 04, 2023 at 12:48:00PM +0200, AngeloGioacchino Del Regno wrote:
> For the eDP case we can support using aux-bus on MediaTek DP: this
> gives us the possibility to declare our panel as generic "panel-edp"
> which will automatically configure the timings and available modes
> via the EDID that we read from it.
>
> To do this, move the panel parsing at the end of the probe function
> so that the hardware is initialized beforehand and also initialize
> the DPTX AUX block and power both on as, when we populate the
> aux-bus, the panel driver will trigger an EDID read to perform
> panel detection.
>
> Last but not least, since now the AUX transfers can happen in the
> separated aux-bus, it was necessary to add an exclusion for the
> cable_plugged_in check in `mtk_dp_aux_transfer()` and the easiest
> way to do this is to simply ignore checking that when the bridge
> type is eDP.
>
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/mediatek/mtk_dp.c | 61 ++++++++++++++++++++++++++-----
> 1 file changed, 51 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
> index a67143c22024..8109f5b4392b 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
[..]
> @@ -2571,6 +2585,33 @@ static int mtk_dp_probe(struct platform_device *pdev)
> mtk_dp->need_debounce = true;
> timer_setup(&mtk_dp->debounce_timer, mtk_dp_debounce_timer, 0);
>
> + if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP) {
> + /* Initialize, reset and poweron the DPTX AUX block */
> + mtk_dp_initialize_aux_settings(mtk_dp);
> + mtk_dp_power_enable(mtk_dp);
> +
> + /* Power on the panel to allow EDID read from aux-bus */
> + mtk_dp_aux_panel_poweron(mtk_dp, true);
> +
> + ret = devm_of_dp_aux_populate_bus(&mtk_dp->aux, NULL);
> +
> + /* If the panel is present, detection is done: power off! */
> + mtk_dp_aux_panel_poweron(mtk_dp, false);
> + mtk_dp_power_disable(mtk_dp);
> +
> + /* We ignore -ENODEV error, as the panel may not be on aux-bus */
> + if (ret && ret != -ENODEV)
> + return ret;
> +
> + /*
> + * Here we don't ignore any error, as if there's no panel to
> + * link, eDP is not configured correctly and will be unusable.
> + */
> + ret = mtk_dp_edp_link_panel(&mtk_dp->aux);
This call might return EDEFER_PROBE if the panel hasn't probed yet. That's a
problem, because during this probe you register a device for the dp-phy, so
you'll be retriggering defer probes every time you probe until the panel probes.
But if this driver was builtin and the panel a module, then this loop will go on
forever.
You should make use of the done_probing callback in
devm_of_dp_aux_populate_bus() and do the panel linking there. This way you can
exit successfully from this probe and avoid the loop. I had to do the same thing
for anx7625.c [1].
Thanks,
Nícolas
[1] https://lore.kernel.org/all/20230518193902.891121-1-nfraprado@xxxxxxxxxxxxx/
