drm/bridge: dw-hdmi-qp: Add support for missing HPD

Add support for the dw-hdmi-qp driver to handle devices with missing
HPD pins.

Since in this situation we are now polling for the EDID data via i2c
change the error message to a rate limited debug message when we are
unable to complete an i2c read, as a disconnected device would
otherwise fill dmesg with i2c read errors.

Reviewed-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/20251119225526.70588-3-macroalpha82@gmail.com

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
index fe4c026280f03465de178dfbefbdd3cf468988db..0c7ad06aaca41129e42921da0e9361375a7e5a22 100644 (file)
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
@@ -165,6 +165,7 @@ struct dw_hdmi_qp {
        struct regmap *regm;
 
        unsigned long tmds_char_rate;
+       bool no_hpd;
 };
 
 static void dw_hdmi_qp_write(struct dw_hdmi_qp *hdmi, unsigned int val,
@@ -555,14 +556,22 @@ static int dw_hdmi_qp_i2c_read(struct dw_hdmi_qp *hdmi,
 
                stat = wait_for_completion_timeout(&i2c->cmp, HZ / 10);
                if (!stat) {
-                       dev_err(hdmi->dev, "i2c read timed out\n");
+                       if (hdmi->no_hpd)
+                               dev_dbg_ratelimited(hdmi->dev,
+                                                   "i2c read timed out\n");
+                       else
+                               dev_err(hdmi->dev, "i2c read timed out\n");
                        dw_hdmi_qp_write(hdmi, 0x01, I2CM_CONTROL0);
                        return -EAGAIN;
                }
 
                /* Check for error condition on the bus */
                if (i2c->stat & I2CM_NACK_RCVD_IRQ) {
-                       dev_err(hdmi->dev, "i2c read error\n");
+                       if (hdmi->no_hpd)
+                               dev_dbg_ratelimited(hdmi->dev,
+                                                   "i2c read error\n");
+                       else
+                               dev_err(hdmi->dev, "i2c read error\n");
                        dw_hdmi_qp_write(hdmi, 0x01, I2CM_CONTROL0);
                        return -EIO;
                }
@@ -900,6 +909,15 @@ static enum drm_connector_status
 dw_hdmi_qp_bridge_detect(struct drm_bridge *bridge, struct drm_connector *connector)
 {
        struct dw_hdmi_qp *hdmi = bridge->driver_private;
+       const struct drm_edid *drm_edid;
+
+       if (hdmi->no_hpd) {
+               drm_edid = drm_edid_read_ddc(connector, bridge->ddc);
+               if (drm_edid)
+                       return connector_status_connected;
+               else
+                       return connector_status_disconnected;
+       }
 
        return hdmi->phy.ops->read_hpd(hdmi, hdmi->phy.data);
 }
@@ -925,6 +943,11 @@ dw_hdmi_qp_bridge_tmds_char_rate_valid(const struct drm_bridge *bridge,
 {
        struct dw_hdmi_qp *hdmi = bridge->driver_private;
 
+       /*
+        * TODO: when hdmi->no_hpd is 1 we must not support modes that
+        * require scrambling, including every mode with a clock above
+        * HDMI14_MAX_TMDSCLK.
+        */
        if (rate > HDMI14_MAX_TMDSCLK) {
                dev_dbg(hdmi->dev, "Unsupported TMDS char rate: %lld\n", rate);
                return MODE_CLOCK_HIGH;
@@ -1277,12 +1300,15 @@ struct dw_hdmi_qp *dw_hdmi_qp_bind(struct platform_device *pdev,
        if (ret)
                return ERR_PTR(ret);
 
+       hdmi->no_hpd = device_property_read_bool(dev, "no-hpd");
+
        hdmi->bridge.driver_private = hdmi;
        hdmi->bridge.ops = DRM_BRIDGE_OP_DETECT |
                           DRM_BRIDGE_OP_EDID |
                           DRM_BRIDGE_OP_HDMI |
-                          DRM_BRIDGE_OP_HDMI_AUDIO |
-                          DRM_BRIDGE_OP_HPD;
+                          DRM_BRIDGE_OP_HDMI_AUDIO;
+       if (!hdmi->no_hpd)
+               hdmi->bridge.ops |= DRM_BRIDGE_OP_HPD;
        hdmi->bridge.of_node = pdev->dev.of_node;
        hdmi->bridge.type = DRM_MODE_CONNECTOR_HDMIA;
        hdmi->bridge.vendor = "Synopsys";