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SubjectRe: [PATCH 3/4] drm/sun4i: dsi: Allow binding the host without a panel
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Maxime,

On 2/11/20 1:28 AM, Samuel Holland wrote:
> Currently, the DSI host blocks binding the display pipeline until the
> panel is available. This unnecessarily prevents other display outpus
> from working, and adds logspam to dmesg when the panel driver is built
> as a module (the component master is unsuccessfully brought up several
> times during boot).
>
> Flip the dependency, instead requiring the host to be bound before the
> panel is attached. The panel driver provides no functionality outside of
> the display pipeline anyway.
>
> Since the panel is now probed after the DRM connector, we need a hotplug
> event to turn on the connector after the panel is attached.
>
> This has the added benefit of fixing panel module removal/insertion.
> Previously, the panel would be turned off when its module was removed.
> But because the connector state was hardcoded, nothing knew to turn the
> panel back on when it was re-attached. Now, with hotplug events
> available, the connector state will follow the panel module state, and
> the panel will be re-enabled properly.
>
> Fixes: 133add5b5ad4 ("drm/sun4i: Add Allwinner A31 MIPI-DSI controller support")
> Signed-off-by: Samuel Holland <samuel@sholland.org>
> ---
> drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 22 ++++++++++++++++------
> drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h | 1 +
> 2 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 019fdf4ec274..ef35ce5a9bb0 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -804,7 +804,10 @@ static struct drm_connector_helper_funcs sun6i_dsi_connector_helper_funcs = {
> static enum drm_connector_status
> sun6i_dsi_connector_detect(struct drm_connector *connector, bool force)
> {
> - return connector_status_connected;
> + struct sun6i_dsi *dsi = connector_to_sun6i_dsi(connector);
> +
> + return dsi->panel ? connector_status_connected :
> + connector_status_disconnected;
> }
>
> static const struct drm_connector_funcs sun6i_dsi_connector_funcs = {
> @@ -945,10 +948,15 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
>
> if (IS_ERR(panel))
> return PTR_ERR(panel);
> + if (!dsi->drm)
> + return -EPROBE_DEFER;

There's actually a bug here. If the panel and DSI drivers are loaded in
parallel, sun6i_dsi_attach() can be called after sun6i_dsi_bind() but before
sun4i_framebuffer_init() initializes drm->mode_config.funcs, causing the hotplug
call to crash. This check also needs to consider dsi->drm->registered before
allowing the panel to be added.

I can send a v2 or a follow-up, whichever you prefer.

Thanks,
Samuel

> dsi->panel = panel;
> dsi->device = device;
>
> + drm_panel_attach(dsi->panel, &dsi->connector);
> + drm_kms_helper_hotplug_event(dsi->drm);
> +
> dev_info(host->dev, "Attached device %s\n", device->name);
>
> return 0;
> @@ -958,10 +966,14 @@ static int sun6i_dsi_detach(struct mipi_dsi_host *host,
> struct mipi_dsi_device *device)
> {
> struct sun6i_dsi *dsi = host_to_sun6i_dsi(host);
> + struct drm_panel *panel = dsi->panel;
>
> dsi->panel = NULL;
> dsi->device = NULL;
>
> + drm_panel_detach(panel);
> + drm_kms_helper_hotplug_event(dsi->drm);
> +
> return 0;
> }
>
> @@ -1026,9 +1038,6 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
> struct sun6i_dsi *dsi = dev_get_drvdata(dev);
> int ret;
>
> - if (!dsi->panel)
> - return -EPROBE_DEFER;
> -
> drm_encoder_helper_add(&dsi->encoder,
> &sun6i_dsi_enc_helper_funcs);
> ret = drm_encoder_init(drm,
> @@ -1054,7 +1063,8 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
> }
>
> drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
> - drm_panel_attach(dsi->panel, &dsi->connector);
> +
> + dsi->drm = drm;
>
> return 0;
>
> @@ -1068,7 +1078,7 @@ static void sun6i_dsi_unbind(struct device *dev, struct device *master,
> {
> struct sun6i_dsi *dsi = dev_get_drvdata(dev);
>
> - drm_panel_detach(dsi->panel);
> + dsi->drm = NULL;
> }
>
> static const struct component_ops sun6i_dsi_ops = {
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> index 61e88ea6044d..c863900ae3b4 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> @@ -29,6 +29,7 @@ struct sun6i_dsi {
>
> struct device *dev;
> struct mipi_dsi_device *device;
> + struct drm_device *drm;
> struct drm_panel *panel;
> };
>
>

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