Hi,
On 11/06/2025 08:29, Jayesh Choudhary wrote:
> 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.krummenac...@toradex.com>
> Signed-off-by: Jayesh Choudhary <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/>
>
> 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
This comment also is written like a commit description ("now that HPD
makes sense").
> + * 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.
> + */
> +
As Doug mentioned, the style here is more like a commit message. But
also, in my opinion, it would make more sense to have the comment in
hpd_enable() rather than having it here, mentioning that the chip needs
to be powered to have a reliable HPD due to the long debounce time.
> 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);
No need for _sync, afaics. Why not pm_runtime_put_autosuspend()?
Tomi
> +}
> +
> 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);
>
