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Message-ID: <20250611052947.5776-1-j-choudhary@ti.com>
Date: Wed, 11 Jun 2025 10:59:47 +0530
From: Jayesh Choudhary <j-choudhary@...com>
To: <dianders@...omium.org>, <andrzej.hajda@...el.com>,
<neil.armstrong@...aro.org>, <rfoss@...nel.org>,
<Laurent.pinchart@...asonboard.com>, <dri-devel@...ts.freedesktop.org>,
<tomi.valkeinen@...asonboard.com>, <max.krummenacher@...adex.com>,
<ernestvanhoecke@...il.com>
CC: <jonas@...boo.se>, <jernej.skrabec@...il.com>,
<maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
<tzimmermann@...e.de>, <airlied@...il.com>, <simona@...ll.ch>,
<kieran.bingham+renesas@...asonboard.com>,
<linux-kernel@...r.kernel.org>, <max.oss.09@...il.com>,
<devarsht@...com>, <j-choudhary@...com>, <geert@...ux-m68k.org>
Subject: [PATCH v4] drm/bridge: ti-sn65dsi86: Add HPD for DisplayPort connector type
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 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@...adex.com>
Signed-off-by: Jayesh Choudhary <j-choudhary@...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-choudhary@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-choudhary@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-choudhary@ti.com/>
[1]: <https://lore.kernel.org/all/mwh35anw57d6nvre3sguetzq3miu4kd43rokegvul7fk266lys@5h2euthpk7vq/>
drivers/gpu/drm/bridge/ti-sn65dsi86.c | 49 ++++++++++++++++++++++-----
1 file changed, 41 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index 60224f476e1d..b674a1aa1a37 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -348,12 +348,20 @@ 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 connector type, now that HPD makes sense and is
+ * required, use the connector type to conditionally disable HPD.
+ *
+ * NOTE: The bridge type is set in auxiliary_bridge probe but
+ * enable_comms() can be called before. So for DisplayPort,
+ * HPD will be enabled once bridge type is set.
+ * "no-hpd" property is not used properly in devicetree description
+ * and hence is unreliable. Therefore HPD is being enabled using
+ * this conditional.
*/
- 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 +1203,17 @@ 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);
+ /*
+ * The chip won't report HPD right after being powered on as
+ * HPD_DEBOUNCED_STATE reflects correct state only after the
+ * debounce time (~100-400 ms).
+ * So having pm_runtime_get_sync() and immediately reading
+ * the register in detect() won't work, and adding delay()
+ * in detect will have performace impact in display.
+ * So remove runtime calls here.
+ */
+
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 +1236,20 @@ 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);
+
+ 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_sync(pdata->dev);
+}
+
static const struct drm_bridge_funcs ti_sn_bridge_funcs = {
.attach = ti_sn_bridge_attach,
.detach = ti_sn_bridge_detach,
@@ -1234,6 +1264,8 @@ 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,
@@ -1322,7 +1354,8 @@ static int ti_sn_bridge_probe(struct auxiliary_device *adev,
? 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;
+ pdata->bridge.ops = DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_DETECT |
+ DRM_BRIDGE_OP_HPD;
drm_bridge_add(&pdata->bridge);
--
2.34.1
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