6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jayesh Choudhary j-choudhary@ti.com
[ Upstream commit 55e8ff842051b1150461d7595d8f1d033c69d66b ]
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.krummenacher@toradex.com Reviewed-by: Douglas Anderson dianders@chromium.org Tested-by: Ernest Van Hoecke ernest.vanhoecke@toradex.com Signed-off-by: Jayesh Choudhary j-choudhary@ti.com Signed-off-by: Douglas Anderson dianders@chromium.org Link: https://lore.kernel.org/r/20250624044835.165708-1-j-choudhary@ti.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/bridge/ti-sn65dsi86.c | 69 +++++++++++++++++++++++---- 1 file changed, 60 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c index 3e31a0c5a6d25..002f8aaa509bc 100644 --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c @@ -331,12 +331,18 @@ 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;
@@ -1173,9 +1179,14 @@ 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; @@ -1198,6 +1209,26 @@ 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_put_autosuspend(pdata->dev); +} + static const struct drm_bridge_funcs ti_sn_bridge_funcs = { .attach = ti_sn_bridge_attach, .detach = ti_sn_bridge_detach, @@ -1212,6 +1243,8 @@ 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, @@ -1300,8 +1333,26 @@ 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);