| Message ID | 20220510122726.v3.4.Ia6324ebc848cd40b4dbd3ad3289a7ffb5c197779@changeid (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | drm/dp: Make DP AUX bus usage easier; use it on ps8640 | expand |
On 10/05/2022 22:29, Douglas Anderson wrote: > While it works, for the most part, to assume that the panel has > finished probing when devm_of_dp_aux_populate_ep_devices() returns, > it's a bit fragile. This is talked about at length in commit > a1e3667a9835 ("drm/bridge: ti-sn65dsi86: Promote the AUX channel to > its own sub-dev"). > > When reviewing the ps8640 code, I managed to convince myself that it > was OK not to worry about it there and that maybe it wasn't really > _that_ fragile. However, it turns out that it really is. Simply > hardcoding panel_edp_probe() to return -EPROBE_DEFER was enough to put > the boot process into an infinite loop. I believe this manages to trip > the same issues that we used to trip with the main MSM code where > something about our actions trigger Linux to re-probe previously > deferred devices right away and each time we try again we re-trigger > Linux to re-probe. > > Let's fix this using the callback introduced in the patch ("drm/dp: > Callbacks to make it easier for drivers to use DP AUX bus properly"). > When using the new callback, we have to be a little careful. The > probe_done() callback is no longer always called in the context of > our probe routine. That means we can't rely on being able to return > -EPROBE_DEFER from it. We re-jigger the order of things a bit to > account for that. > > With this change, the device still boots (though obviously the panel > doesn't come up) if I force panel-edp to always return > -EPROBE_DEFER. If I fake it and make the panel probe exactly once it > also works. > > Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > --- > > Changes in v3: > - Adapt to v3 changes in aux bus. > - Use devm_drm_bridge_add() to simplify. > > Changes in v2: > - Rewrote atop new method introduced by patch #1. > > drivers/gpu/drm/bridge/parade-ps8640.c | 74 ++++++++++++++++---------- > 1 file changed, 46 insertions(+), 28 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c > index e2467e58b5b7..ff4227f6d800 100644 > --- a/drivers/gpu/drm/bridge/parade-ps8640.c > +++ b/drivers/gpu/drm/bridge/parade-ps8640.c > @@ -537,7 +537,7 @@ static const struct drm_bridge_funcs ps8640_bridge_funcs = { > .pre_enable = ps8640_pre_enable, > }; > > -static int ps8640_bridge_host_attach(struct device *dev, struct ps8640 *ps_bridge) > +static int ps8640_bridge_get_dsi_resources(struct device *dev, struct ps8640 *ps_bridge) > { > struct device_node *in_ep, *dsi_node; > struct mipi_dsi_device *dsi; > @@ -576,13 +576,40 @@ static int ps8640_bridge_host_attach(struct device *dev, struct ps8640 *ps_bridg > dsi->format = MIPI_DSI_FMT_RGB888; > dsi->lanes = NUM_MIPI_LANES; > > - return devm_mipi_dsi_attach(dev, dsi); > + return 0; > +} > + > +static int ps8640_bridge_link_panel(struct drm_dp_aux *aux) > +{ > + struct ps8640 *ps_bridge = aux_to_ps8640(aux); > + struct device *dev = aux->dev; > + struct device_node *np = dev->of_node; > + int ret; > + > + /* > + * NOTE about returning -EPROBE_DEFER from this function: if we > + * return an error (most relevant to -EPROBE_DEFER) it will only > + * be passed out to ps8640_probe() if it called this directly (AKA the > + * panel isn't under the "aux-bus" node). That should be fine because > + * if the panel is under "aux-bus" it's guaranteed to have probed by > + * the time this function has been called. > + */ > + > + /* port@1 is ps8640 output port */ > + ps_bridge->panel_bridge = devm_drm_of_get_bridge(dev, np, 1, 0); > + if (IS_ERR(ps_bridge->panel_bridge)) > + return PTR_ERR(ps_bridge->panel_bridge); > + > + ret = devm_drm_bridge_add(dev, &ps_bridge->bridge); > + if (ret) > + return ret; > + > + return devm_mipi_dsi_attach(dev, ps_bridge->dsi); > } > > static int ps8640_probe(struct i2c_client *client) > { > struct device *dev = &client->dev; > - struct device_node *np = dev->of_node; > struct ps8640 *ps_bridge; > int ret; > u32 i; > @@ -623,6 +650,14 @@ static int ps8640_probe(struct i2c_client *client) > if (!ps8640_of_panel_on_aux_bus(&client->dev)) > ps_bridge->bridge.ops = DRM_BRIDGE_OP_EDID; > > + /* > + * Get MIPI DSI resources early. These can return -EPROBE_DEFER so > + * we want to get them out of the way sooner. > + */ > + ret = ps8640_bridge_get_dsi_resources(&client->dev, ps_bridge); > + if (ret) > + return ret; > + > ps_bridge->page[PAGE0_DP_CNTL] = client; > > ps_bridge->regmap[PAGE0_DP_CNTL] = devm_regmap_init_i2c(client, ps8640_regmap_config); > @@ -665,35 +700,19 @@ static int ps8640_probe(struct i2c_client *client) > if (ret) > return ret; > > - devm_of_dp_aux_populate_ep_devices(&ps_bridge->aux); > + ret = devm_of_dp_aux_populate_bus(&ps_bridge->aux, ps8640_bridge_link_panel); > > - /* port@1 is ps8640 output port */ > - ps_bridge->panel_bridge = devm_drm_of_get_bridge(dev, np, 1, 0); > - if (IS_ERR(ps_bridge->panel_bridge)) > - return PTR_ERR(ps_bridge->panel_bridge); > - > - drm_bridge_add(&ps_bridge->bridge); > - > - ret = ps8640_bridge_host_attach(dev, ps_bridge); > - if (ret) > - goto err_bridge_remove; > - > - return 0; > + /* > + * If devm_of_dp_aux_populate_bus() returns -ENODEV then it's up to > + * usa to call ps8640_bridge_link_panel() directly. NOTE: in this case > + * the function is allowed to -EPROBE_DEFER. > + */ > + if (ret == -ENODEV) > + return ps8640_bridge_link_panel(&ps_bridge->aux); > > -err_bridge_remove: > - drm_bridge_remove(&ps_bridge->bridge); > return ret; > } > > -static int ps8640_remove(struct i2c_client *client) > -{ > - struct ps8640 *ps_bridge = i2c_get_clientdata(client); > - > - drm_bridge_remove(&ps_bridge->bridge); > - > - return 0; > -} > - > static const struct of_device_id ps8640_match[] = { > { .compatible = "parade,ps8640" }, > { } > @@ -702,7 +721,6 @@ MODULE_DEVICE_TABLE(of, ps8640_match); > > static struct i2c_driver ps8640_driver = { > .probe_new = ps8640_probe, > - .remove = ps8640_remove, > .driver = { > .name = "ps8640", > .of_match_table = ps8640_match,
diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c index e2467e58b5b7..ff4227f6d800 100644 --- a/drivers/gpu/drm/bridge/parade-ps8640.c +++ b/drivers/gpu/drm/bridge/parade-ps8640.c @@ -537,7 +537,7 @@ static const struct drm_bridge_funcs ps8640_bridge_funcs = { .pre_enable = ps8640_pre_enable, }; -static int ps8640_bridge_host_attach(struct device *dev, struct ps8640 *ps_bridge) +static int ps8640_bridge_get_dsi_resources(struct device *dev, struct ps8640 *ps_bridge) { struct device_node *in_ep, *dsi_node; struct mipi_dsi_device *dsi; @@ -576,13 +576,40 @@ static int ps8640_bridge_host_attach(struct device *dev, struct ps8640 *ps_bridg dsi->format = MIPI_DSI_FMT_RGB888; dsi->lanes = NUM_MIPI_LANES; - return devm_mipi_dsi_attach(dev, dsi); + return 0; +} + +static int ps8640_bridge_link_panel(struct drm_dp_aux *aux) +{ + struct ps8640 *ps_bridge = aux_to_ps8640(aux); + struct device *dev = aux->dev; + struct device_node *np = dev->of_node; + int ret; + + /* + * NOTE about returning -EPROBE_DEFER from this function: if we + * return an error (most relevant to -EPROBE_DEFER) it will only + * be passed out to ps8640_probe() if it called this directly (AKA the + * panel isn't under the "aux-bus" node). That should be fine because + * if the panel is under "aux-bus" it's guaranteed to have probed by + * the time this function has been called. + */ + + /* port@1 is ps8640 output port */ + ps_bridge->panel_bridge = devm_drm_of_get_bridge(dev, np, 1, 0); + if (IS_ERR(ps_bridge->panel_bridge)) + return PTR_ERR(ps_bridge->panel_bridge); + + ret = devm_drm_bridge_add(dev, &ps_bridge->bridge); + if (ret) + return ret; + + return devm_mipi_dsi_attach(dev, ps_bridge->dsi); } static int ps8640_probe(struct i2c_client *client) { struct device *dev = &client->dev; - struct device_node *np = dev->of_node; struct ps8640 *ps_bridge; int ret; u32 i; @@ -623,6 +650,14 @@ static int ps8640_probe(struct i2c_client *client) if (!ps8640_of_panel_on_aux_bus(&client->dev)) ps_bridge->bridge.ops = DRM_BRIDGE_OP_EDID; + /* + * Get MIPI DSI resources early. These can return -EPROBE_DEFER so + * we want to get them out of the way sooner. + */ + ret = ps8640_bridge_get_dsi_resources(&client->dev, ps_bridge); + if (ret) + return ret; + ps_bridge->page[PAGE0_DP_CNTL] = client; ps_bridge->regmap[PAGE0_DP_CNTL] = devm_regmap_init_i2c(client, ps8640_regmap_config); @@ -665,35 +700,19 @@ static int ps8640_probe(struct i2c_client *client) if (ret) return ret; - devm_of_dp_aux_populate_ep_devices(&ps_bridge->aux); + ret = devm_of_dp_aux_populate_bus(&ps_bridge->aux, ps8640_bridge_link_panel); - /* port@1 is ps8640 output port */ - ps_bridge->panel_bridge = devm_drm_of_get_bridge(dev, np, 1, 0); - if (IS_ERR(ps_bridge->panel_bridge)) - return PTR_ERR(ps_bridge->panel_bridge); - - drm_bridge_add(&ps_bridge->bridge); - - ret = ps8640_bridge_host_attach(dev, ps_bridge); - if (ret) - goto err_bridge_remove; - - return 0; + /* + * If devm_of_dp_aux_populate_bus() returns -ENODEV then it's up to + * usa to call ps8640_bridge_link_panel() directly. NOTE: in this case + * the function is allowed to -EPROBE_DEFER. + */ + if (ret == -ENODEV) + return ps8640_bridge_link_panel(&ps_bridge->aux); -err_bridge_remove: - drm_bridge_remove(&ps_bridge->bridge); return ret; } -static int ps8640_remove(struct i2c_client *client) -{ - struct ps8640 *ps_bridge = i2c_get_clientdata(client); - - drm_bridge_remove(&ps_bridge->bridge); - - return 0; -} - static const struct of_device_id ps8640_match[] = { { .compatible = "parade,ps8640" }, { } @@ -702,7 +721,6 @@ MODULE_DEVICE_TABLE(of, ps8640_match); static struct i2c_driver ps8640_driver = { .probe_new = ps8640_probe, - .remove = ps8640_remove, .driver = { .name = "ps8640", .of_match_table = ps8640_match,
While it works, for the most part, to assume that the panel has finished probing when devm_of_dp_aux_populate_ep_devices() returns, it's a bit fragile. This is talked about at length in commit a1e3667a9835 ("drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev"). When reviewing the ps8640 code, I managed to convince myself that it was OK not to worry about it there and that maybe it wasn't really _that_ fragile. However, it turns out that it really is. Simply hardcoding panel_edp_probe() to return -EPROBE_DEFER was enough to put the boot process into an infinite loop. I believe this manages to trip the same issues that we used to trip with the main MSM code where something about our actions trigger Linux to re-probe previously deferred devices right away and each time we try again we re-trigger Linux to re-probe. Let's fix this using the callback introduced in the patch ("drm/dp: Callbacks to make it easier for drivers to use DP AUX bus properly"). When using the new callback, we have to be a little careful. The probe_done() callback is no longer always called in the context of our probe routine. That means we can't rely on being able to return -EPROBE_DEFER from it. We re-jigger the order of things a bit to account for that. With this change, the device still boots (though obviously the panel doesn't come up) if I force panel-edp to always return -EPROBE_DEFER. If I fake it and make the panel probe exactly once it also works. Signed-off-by: Douglas Anderson <dianders@chromium.org> --- Changes in v3: - Adapt to v3 changes in aux bus. - Use devm_drm_bridge_add() to simplify. Changes in v2: - Rewrote atop new method introduced by patch #1. drivers/gpu/drm/bridge/parade-ps8640.c | 74 ++++++++++++++++---------- 1 file changed, 46 insertions(+), 28 deletions(-)