On Wed, 5 Jan 2022 at 10:08, AngeloGioacchino Del Regno
<angelogioacchino.delregno@xxxxxxxxxxxxx> wrote:
>
> Entering suspend while the display attached to this bridge is still on
> makes the resume sequence to resume the bridge first, display last:
> when this happens, we get a timeout while resuming the bridge, as its
> MCU will get stuck due to the display being unpowered.
>
> On the other hand, on mt8173-elm, closing the lid makes the display to
> get powered off first, bridge last, so at resume time the sequence is
> swapped (compared to the first example) and everything just works
> as expected.
>
> Add a stateless device link to the DRM device that this bridge belongs
> to, ensuring a correct resume sequence and solving the unability to
> correctly resume bridge operation in the first mentioned example.
>
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/bridge/parade-ps8640.c | 27 ++++++++++++++++++++++++--
> 1 file changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> index 818704bf5e86..450bc9bdf295 100644
> --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> @@ -102,6 +102,7 @@ struct ps8640 {
> struct regulator_bulk_data supplies[2];
> struct gpio_desc *gpio_reset;
> struct gpio_desc *gpio_powerdown;
> + struct device_link *link;
> bool pre_enabled;
> };
>
> @@ -456,14 +457,36 @@ static int ps8640_bridge_attach(struct drm_bridge *bridge,
> return ret;
> }
>
> + ps_bridge->link = device_link_add(bridge->dev->dev, dev, DL_FLAG_STATELESS);
> + if (!ps_bridge->link) {
> + dev_err(dev, "failed to create device link");
> + ret = -EINVAL;
> + goto err_devlink;
> + }
> +
> /* Attach the panel-bridge to the dsi bridge */
> - return drm_bridge_attach(bridge->encoder, ps_bridge->panel_bridge,
> + ret = drm_bridge_attach(bridge->encoder, ps_bridge->panel_bridge,
> &ps_bridge->bridge, flags);
Bad alignment according to checkpatch --strict
> + if (ret)
> + goto err_bridge_attach;
> +
> + return 0;
> +
> +err_bridge_attach:
> + device_link_del(ps_bridge->link);
> +err_devlink:
> + drm_dp_aux_unregister(&ps_bridge->aux);
> +
> + return ret;
> }
>
> static void ps8640_bridge_detach(struct drm_bridge *bridge)
> {
> - drm_dp_aux_unregister(&bridge_to_ps8640(bridge)->aux);
> + struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
> +
> + drm_dp_aux_unregister(&ps_bridge->aux);
> + if (ps_bridge->link)
> + device_link_del(ps_bridge->link);
> }
>
> static struct edid *ps8640_bridge_get_edid(struct drm_bridge *bridge,
> --
> 2.33.1
>
Fixed alignment issue, applied to drm-misc-next and added r-b tag.
Reviewed-by: Robert Foss <robert.foss@xxxxxxxxxx>
