There's cross-talk on the RPi4 between the 2.4GHz channels used by the WiFi chip and some resolutions, most notably 1440p at 60Hz.
In such a case, we can either reject entirely the mode, or lower slightly the pixel frequency to remove the overlap. Let's go for the latter.
Signed-off-by: Maxime Ripard maxime@cerno.tech --- .../bindings/display/brcm,bcm2711-hdmi.yaml | 6 ++++++ drivers/gpu/drm/vc4/vc4_hdmi.c | 14 +++++++++++++- drivers/gpu/drm/vc4/vc4_hdmi.h | 8 ++++++++ 3 files changed, 27 insertions(+), 1 deletion(-)
diff --git a/Documentation/devicetree/bindings/display/brcm,bcm2711-hdmi.yaml b/Documentation/devicetree/bindings/display/brcm,bcm2711-hdmi.yaml index 03a76729d26c..63e7fe999c0a 100644 --- a/Documentation/devicetree/bindings/display/brcm,bcm2711-hdmi.yaml +++ b/Documentation/devicetree/bindings/display/brcm,bcm2711-hdmi.yaml @@ -76,6 +76,12 @@ properties: resets: maxItems: 1
+ raspberrypi,disable-wifi-frequencies: + type: boolean + description: > + Should the pixel frequencies in the WiFi frequencies range be + avoided? + required: - compatible - reg diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c index acfb4e235214..74da7c00ecd0 100644 --- a/drivers/gpu/drm/vc4/vc4_hdmi.c +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c @@ -877,13 +877,22 @@ static int vc4_hdmi_encoder_atomic_check(struct drm_encoder *encoder, struct vc4_hdmi_connector_state *vc4_state = conn_state_to_vc4_hdmi_conn_state(conn_state); struct drm_display_mode *mode = &crtc_state->adjusted_mode; struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder); - unsigned long long pixel_rate = mode->clock * 1000; + unsigned long long pixel_rate;
if (vc4_hdmi->variant->broken_odd_h_timings && ((mode->hdisplay % 2) || (mode->hsync_start % 2) || (mode->hsync_end % 2) || (mode->htotal % 2))) return -EINVAL;
+ /* + * The 1440p@60 pixel rate is in the same range than the WiFi + * channels. Slightly lower the frequency to bring it out of the + * WiFi range. + */ + if (vc4_hdmi->disable_wifi_frequencies && mode->clock == 241500) + mode->clock = 238560; + + pixel_rate = mode->clock * 1000; if (mode->flags & DRM_MODE_FLAG_DBLCLK) pixel_rate *= 2;
@@ -1837,6 +1846,9 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data) vc4_hdmi->hpd_active_low = hpd_gpio_flags & OF_GPIO_ACTIVE_LOW; }
+ vc4_hdmi->disable_wifi_frequencies = + of_property_read_bool(dev->of_node, "raspberrypi,disable-wifi-frequencies"); + pm_runtime_enable(dev);
drm_simple_encoder_init(drm, encoder, DRM_MODE_ENCODER_TMDS); diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h index 40e51ece8efe..6618ee758890 100644 --- a/drivers/gpu/drm/vc4/vc4_hdmi.h +++ b/drivers/gpu/drm/vc4/vc4_hdmi.h @@ -143,6 +143,14 @@ struct vc4_hdmi { int hpd_gpio; bool hpd_active_low;
+ /* + * On some systems (like the RPi4), some modes are in the same + * frequency range than the WiFi channels (1440p@60Hz for + * example). Should we take evasive actions because that system + * has a wifi adapter. + */ + bool disable_wifi_frequencies; + struct cec_adapter *cec_adap; struct cec_msg cec_rx_msg; bool cec_tx_ok;