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drm/vc4: hdmi: Disable Wifi Frequencies

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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>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20201029134018.1948636-2-maxime@cerno.tech
This commit is contained in:
Maxime Ripard 2020-10-29 14:40:17 +01:00
parent 8d15aa4ed0
commit 9fa1d7e60a
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GPG Key ID: E3EF0D6F671851C5
2 changed files with 29 additions and 0 deletions
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21
drivers/gpu/drm/vc4/vc4_hdmi.c
View File

@ -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);

8
drivers/gpu/drm/vc4/vc4_hdmi.h
View File

@ -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;