By default, HPD was disabled on SN65DSI86 bridge. When the driver was added (commit "a095f15c00e27"), the HPD_DISABLE bit was set in pre-enable call which was moved to other function calls subsequently. Later on, commit "c312b0df3b13" added detect utility for DP mode. But with HPD_DISABLE bit set, all the HPD events are disabled[0] and the debounced state always return 1 (always connected state).
Set HPD_DISABLE bit conditionally based on display sink's connector type. Since the HPD_STATE is reflected correctly only after waiting for debounce time (~100-400ms) and adding this delay in detect() is not feasible owing to the performace impact (glitches and frame drop), remove runtime calls in detect() and add hpd_enable()/disable() bridge hooks with runtime calls, to detect hpd properly without any delay. [0]: <https://www.ti.com/lit/gpn/SN65DSI86> (Pg. 32) Fixes: c312b0df3b13 ("drm/bridge: ti-sn65dsi86: Implement bridge connector operations for DP") Cc: Max Krummenacher <max.krummenac...@toradex.com> Signed-off-by: Jayesh Choudhary <j-choudh...@ti.com> --- Changelog v4->v5: - Make suspend asynchronous in hpd_disable() - Update HPD_DISABLE in probe function to address the case for when comms are already enabled. Comments taken verbatim from [2] - Update comments v4 patch: <https://lore.kernel.org/all/20250611052947.5776-1-j-choudh...@ti.com/> Changelog v3->v4: - Remove "no-hpd" support due to backward compatibility issues - Change the conditional from "no-hpd" back to connector type but still address [1] v3 patch link: <https://lore.kernel.org/all/20250529110418.481756-1-j-choudh...@ti.com/> Changelog v2->v3: - Change conditional based on no-hpd property to address [1] - Remove runtime calls in detect() with appropriate comments - Add hpd_enable() and hpd_disable() in drm_bridge_funcs v2 patch link: <https://lore.kernel.org/all/20250508115433.449102-1-j-choudh...@ti.com/> Changelog v1->v2: - Drop additional property in bindings and use conditional. - Instead of register read for HPD state, use dpcd read which returns 0 for success and error codes for no connection - Add relevant history for the required change in commit message - Drop RFC subject-prefix in v2 - Add "Cc:" tag v1 patch link: <https://lore.kernel.org/all/20250424105432.255309-1-j-choudh...@ti.com/> [1]: <https://lore.kernel.org/all/mwh35anw57d6nvre3sguetzq3miu4kd43rokegvul7fk266lys@5h2euthpk7vq/> [2]: <https://lore.kernel.org/all/CAD=FV=WvH73d78De3PrbiG7b6OaS_BysGtxQ=mjtj4z-h0l...@mail.gmail.com/> drivers/gpu/drm/bridge/ti-sn65dsi86.c | 70 +++++++++++++++++++++++---- 1 file changed, 61 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c index 60224f476e1d..c6a826e8091e 100644 --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c @@ -348,12 +348,18 @@ static void ti_sn65dsi86_enable_comms(struct ti_sn65dsi86 *pdata, * 200 ms. We'll assume that the panel driver will have the hardcoded * delay in its prepare and always disable HPD. * - * If HPD somehow makes sense on some future panel we'll have to - * change this to be conditional on someone specifying that HPD should - * be used. + * For DisplayPort bridge type, we need HPD. So we use the bridge type + * to conditionally disable HPD. + * NOTE: The bridge type is set in ti_sn_bridge_probe() but enable_comms() + * can be called before. So for DisplayPort, HPD will be enabled once + * bridge type is set. We are using bridge type instead of "no-hpd" + * property because it is not used properly in devicetree description + * and hence is unreliable. */ - regmap_update_bits(pdata->regmap, SN_HPD_DISABLE_REG, HPD_DISABLE, - HPD_DISABLE); + + if (pdata->bridge.type != DRM_MODE_CONNECTOR_DisplayPort) + regmap_update_bits(pdata->regmap, SN_HPD_DISABLE_REG, HPD_DISABLE, + HPD_DISABLE); pdata->comms_enabled = true; @@ -1195,9 +1201,14 @@ static enum drm_connector_status ti_sn_bridge_detect(struct drm_bridge *bridge) struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge); int val = 0; - pm_runtime_get_sync(pdata->dev); + /* + * Runtime reference is grabbed in ti_sn_bridge_hpd_enable() + * as the chip won't report HPD just after being powered on. + * HPD_DEBOUNCED_STATE reflects correct state only after the + * debounce time (~100-400 ms). + */ + regmap_read(pdata->regmap, SN_HPD_DISABLE_REG, &val); - pm_runtime_put_autosuspend(pdata->dev); return val & HPD_DEBOUNCED_STATE ? connector_status_connected : connector_status_disconnected; @@ -1220,6 +1231,27 @@ static void ti_sn65dsi86_debugfs_init(struct drm_bridge *bridge, struct dentry * debugfs_create_file("status", 0600, debugfs, pdata, &status_fops); } +static void ti_sn_bridge_hpd_enable(struct drm_bridge *bridge) +{ + struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge); + + /* + * Device needs to be powered on before reading the HPD state + * for reliable hpd detection in ti_sn_bridge_detect() due to + * the high debounce time. + */ + + pm_runtime_get_sync(pdata->dev); +} + +static void ti_sn_bridge_hpd_disable(struct drm_bridge *bridge) +{ + struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge); + + pm_runtime_mark_last_busy(pdata->dev); + pm_runtime_put_autosuspend(pdata->dev); +} + static const struct drm_bridge_funcs ti_sn_bridge_funcs = { .attach = ti_sn_bridge_attach, .detach = ti_sn_bridge_detach, @@ -1234,6 +1266,8 @@ static const struct drm_bridge_funcs ti_sn_bridge_funcs = { .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state, .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state, .debugfs_init = ti_sn65dsi86_debugfs_init, + .hpd_enable = ti_sn_bridge_hpd_enable, + .hpd_disable = ti_sn_bridge_hpd_disable, }; static void ti_sn_bridge_parse_lanes(struct ti_sn65dsi86 *pdata, @@ -1321,8 +1355,26 @@ static int ti_sn_bridge_probe(struct auxiliary_device *adev, pdata->bridge.type = pdata->next_bridge->type == DRM_MODE_CONNECTOR_DisplayPort ? DRM_MODE_CONNECTOR_DisplayPort : DRM_MODE_CONNECTOR_eDP; - if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort) - pdata->bridge.ops = DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_DETECT; + if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort) { + pdata->bridge.ops = DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_DETECT | + DRM_BRIDGE_OP_HPD; + /* + * If comms were already enabled they would have been enabled + * with the wrong value of HPD_DISABLE. Update it now. Comms + * could be enabled if anyone is holding a pm_runtime reference + * (like if a GPIO is in use). Note that in most cases nobody + * is doing AUX channel xfers before the bridge is added so + * HPD doesn't _really_ matter then. The only exception is in + * the eDP case where the panel wants to read the EDID before + * the bridge is added. We always consistently have HPD disabled + * for eDP. + */ + mutex_lock(&pdata->comms_mutex); + if (pdata->comms_enabled) + regmap_update_bits(pdata->regmap, SN_HPD_DISABLE_REG, + HPD_DISABLE, 0); + mutex_unlock(&pdata->comms_mutex); + }; drm_bridge_add(&pdata->bridge); -- 2.34.1
