Unverified Commit 9fa1d7e6 authored by Maxime Ripard's avatar Maxime Ripard
Browse files

drm/vc4: hdmi: Disable Wifi Frequencies 



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: default avatarMaxime Ripard <maxime@cerno.tech>
Acked-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20201029134018.1948636-2-maxime@cerno.tech
parent 8d15aa4e

drivers/gpu/drm/vc4/vc4_hdmi.c

+21 −0
Original line number Diff line number Diff line
@@ -760,6 +760,9 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder) 
{

}



#define WIFI_2_4GHz_CH1_MIN_FREQ	2400000000ULL

#define WIFI_2_4GHz_CH1_MAX_FREQ	2422000000ULL



static int vc4_hdmi_encoder_atomic_check(struct drm_encoder *encoder,

					 struct drm_crtc_state *crtc_state,

					 struct drm_connector_state *conn_state)
@@ -767,12 +770,27 @@ static int vc4_hdmi_encoder_atomic_check(struct drm_encoder *encoder, 
	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 tmds_rate;



	if (vc4_hdmi->variant->unsupported_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 first

	 * WiFi channel (between 2.4GHz and 2.422GHz with 22MHz

	 * bandwidth). Slightly lower the frequency to bring it out of

	 * the WiFi range.

	 */

	tmds_rate = pixel_rate * 10;

	if (vc4_hdmi->disable_wifi_frequencies &&

	    (tmds_rate >= WIFI_2_4GHz_CH1_MIN_FREQ &&

	     tmds_rate <= WIFI_2_4GHz_CH1_MAX_FREQ)) {

		mode->clock = 238560;

		pixel_rate = mode->clock * 1000;

	}



	if (pixel_rate > vc4_hdmi->variant->max_pixel_clock)

		return -EINVAL;
@@ -1719,6 +1737,9 @@ 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, "wifi-2.4ghz-coexistence");



	pm_runtime_enable(dev);



	drm_simple_encoder_init(drm, encoder, DRM_MODE_ENCODER_TMDS);

drivers/gpu/drm/vc4/vc4_hdmi.h

+8 −0
Original line number Diff line number Diff line
@@ -142,6 +142,14 @@ 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;

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