[PATCH 1/2] drm/vc4: hdmi: Disable Wifi Frequencies

[PATCH 1/2] drm/vc4: hdmi: Disable Wifi Frequencies

[Maxime Ripard]

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;
-- 
2.26.2

[PATCH 2/2] ARM: dts: rpi-4: disable wifi frequencies

[Maxime Ripard]

The RPi4 WiFi chip and HDMI outputs have some frequency overlap with
crosstalk around 2.4GHz. Let's mark it as such so we can use some evasive
maneuvers.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 arch/arm/boot/dts/bcm2711-rpi-4-b.dts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/boot/dts/bcm2711-rpi-4-b.dts b/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
index ca24c2c737ab..1b739c3a9a12 100644
--- a/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
+++ b/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
@@ -174,12 +174,14 @@ &gpio {
 &hdmi0 {
 	clocks = <&firmware_clocks 13>, <&firmware_clocks 14>, <&dvp 0>, <&clk_27MHz>;
 	clock-names = "hdmi", "bvb", "audio", "cec";
+	raspberrypi,disable-wifi-frequencies;
 	status = "okay";
 };
 
 &hdmi1 {
 	clocks = <&firmware_clocks 13>, <&firmware_clocks 14>, <&dvp 1>, <&clk_27MHz>;
 	clock-names = "hdmi", "bvb", "audio", "cec";
+	raspberrypi,disable-wifi-frequencies;
 	status = "okay";
 };
 
-- 
2.26.2

Re: [PATCH 1/2] drm/vc4: hdmi: Disable Wifi Frequencies

[Daniel Vetter]

On Mon, Sep 28, 2020 at 9:06 AM Maxime Ripard <maxime@cerno.tech> wrote:
>
> 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;

Don't you want to map for a (narrow) range of frequencies here? Just
for that infamous 60p vs 59.99p thing and similar. And I think that
would still be in that band you want to avoid.
-Daniel

> +
> +       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;
> --
> 2.26.2
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel



-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH 1/2] drm/vc4: hdmi: Disable Wifi Frequencies

[Rob Herring]

On Fri, Sep 25, 2020 at 03:07:43PM +0200, Maxime Ripard wrote:
> 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?

Based on googling the issue, perhaps should be a common property?

Re: [PATCH 1/2] drm/vc4: hdmi: Disable Wifi Frequencies

[Maxime Ripard]

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Hi Daniel,

On Mon, Sep 28, 2020 at 11:02:11AM +0200, Daniel Vetter wrote:
> On Mon, Sep 28, 2020 at 9:06 AM Maxime Ripard <maxime@cerno.tech> wrote:
> >
> > 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;
> 
> Don't you want to map for a (narrow) range of frequencies here? Just
> for that infamous 60p vs 59.99p thing and similar. And I think that
> would still be in that band you want to avoid.

Testing for a range seems better indeed, I'll send a new version

Thanks!
Maxime

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Re: [PATCH 1/2] drm/vc4: hdmi: Disable Wifi Frequencies

[Maxime Ripard]

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Hi Rob,

On Tue, Sep 29, 2020 at 02:00:55PM -0500, Rob Herring wrote:
> On Fri, Sep 25, 2020 at 03:07:43PM +0200, Maxime Ripard wrote:
> > 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?
> 
> Based on googling the issue, perhaps should be a common property?

This is a fairly generic issue indeed, but went for the most
non-intrusive way. Do you have a better idea of a generic name, or do
you just want me to drop the vendor prefix?

Maxime

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