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SubjectRe: [PATCH 1/2] drm/bridge: dw-hdmi: Add DT binding to disable hotplug detect
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On 31/01/2021 10:55, Mykyta Poturai wrote:
> Add "disable-hpd" boolean binding for the device tree. When this option
> is turned on HPD-related IRQ is disabled and it is assumed that the HDMI
> connector is connected all the time. This may be useful in systems where
> it is impossible or undesirable to connect the HPD pin, or the
> connection is broken.

DRM mode forcing exists for this reason.

You can even force an EDID to have a fixed mode.

Neil

>
> Signed-off-by: Mykyta Poturai <ddone@aruko.org>
> ---
> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 0c79a9ba48bb..4ca0ac130beb 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -194,6 +194,7 @@ struct dw_hdmi {
> unsigned int audio_cts;
> unsigned int audio_n;
> bool audio_enable;
> + bool disable_hpd;
>
> unsigned int reg_shift;
> struct regmap *regm;
> @@ -1559,7 +1560,7 @@ static void dw_hdmi_phy_disable(struct dw_hdmi *hdmi, void *data)
> enum drm_connector_status dw_hdmi_phy_read_hpd(struct dw_hdmi *hdmi,
> void *data)
> {
> - return hdmi_readb(hdmi, HDMI_PHY_STAT0) & HDMI_PHY_HPD ?
> + return hdmi_readb(hdmi, HDMI_PHY_STAT0) & HDMI_PHY_HPD || hdmi->disable_hpd ?
> connector_status_connected : connector_status_disconnected;
> }
> EXPORT_SYMBOL_GPL(dw_hdmi_phy_read_hpd);
> @@ -1585,6 +1586,10 @@ void dw_hdmi_phy_setup_hpd(struct dw_hdmi *hdmi, void *data)
> * Configure the PHY RX SENSE and HPD interrupts polarities and clear
> * any pending interrupt.
> */
> +
> + if (hdmi->disable_hpd)
> + return;
> +
> hdmi_writeb(hdmi, HDMI_PHY_HPD | HDMI_PHY_RX_SENSE, HDMI_PHY_POL0);
> hdmi_writeb(hdmi, HDMI_IH_PHY_STAT0_HPD | HDMI_IH_PHY_STAT0_RX_SENSE,
> HDMI_IH_PHY_STAT0);
> @@ -3212,6 +3217,10 @@ struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
> mutex_init(&hdmi->cec_notifier_mutex);
> spin_lock_init(&hdmi->audio_lock);
>
> + if (of_property_read_bool(np, "disable-hpd")) {
> + dev_info(hdmi->dev, "Disabling HPD\n");
> + hdmi->disable_hpd = true;
> + }
> ddc_node = of_parse_phandle(np, "ddc-i2c-bus", 0);
> if (ddc_node) {
> hdmi->ddc = of_get_i2c_adapter_by_node(ddc_node);
>

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