linux-kernel - Re: [PATCH v1] usb: typec: altmodes/displayport: Signal hpd when configuring pin assignment

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Date:   Mon, 31 Jul 2023 15:42:33 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     RD Babiera <rdbabiera@...gle.com>
Cc:     gregkh@...uxfoundation.org, badhri@...gle.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v1] usb: typec: altmodes/displayport: Signal hpd when
 configuring pin assignment

On Wed, Jul 26, 2023 at 02:09:02AM +0000, RD Babiera wrote:
> When connecting to some DisplayPort partners, the initial status update
> after entering DisplayPort Alt Mode notifies that the DFP_D/UFP_D is not in
> the connected state. This leads to sending a configure message that keeps
> the device in USB mode. The port partner then sets DFP_D/UFP_D to the
> connected state and HPD to high in the same Attention message. Currently,
> the HPD signal is dropped in order to handle configuration.
> 
> This patch saves changes to the HPD signal when the device chooses to
> configure during dp_altmode_status_update, and invokes sysfs_notify if
> necessary for HPD after configuring.
> 
> Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode")
> Cc: stable@...r.kernel.org
> Signed-off-by: RD Babiera <rdbabiera@...gle.com>

Acked-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
>  drivers/usb/typec/altmodes/displayport.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
> index 66de880b28d0..cdf8261e22db 100644
> --- a/drivers/usb/typec/altmodes/displayport.c
> +++ b/drivers/usb/typec/altmodes/displayport.c
> @@ -60,6 +60,7 @@ struct dp_altmode {
>  
>  	enum dp_state state;
>  	bool hpd;
> +	bool pending_hpd;
>  
>  	struct mutex lock; /* device lock */
>  	struct work_struct work;
> @@ -144,8 +145,13 @@ static int dp_altmode_status_update(struct dp_altmode *dp)
>  		dp->state = DP_STATE_EXIT;
>  	} else if (!(con & DP_CONF_CURRENTLY(dp->data.conf))) {
>  		ret = dp_altmode_configure(dp, con);
> -		if (!ret)
> +		if (!ret) {
>  			dp->state = DP_STATE_CONFIGURE;
> +			if (dp->hpd != hpd) {
> +				dp->hpd = hpd;
> +				dp->pending_hpd = true;
> +			}
> +		}
>  	} else {
>  		if (dp->hpd != hpd) {
>  			drm_connector_oob_hotplug_event(dp->connector_fwnode);
> @@ -161,6 +167,16 @@ static int dp_altmode_configured(struct dp_altmode *dp)
>  {
>  	sysfs_notify(&dp->alt->dev.kobj, "displayport", "configuration");
>  	sysfs_notify(&dp->alt->dev.kobj, "displayport", "pin_assignment");
> +	/*
> +	 * If the DFP_D/UFP_D sends a change in HPD when first notifying the
> +	 * DisplayPort driver that it is connected, then we wait until
> +	 * configuration is complete to signal HPD.
> +	 */
> +	if (dp->pending_hpd) {
> +		drm_connector_oob_hotplug_event(dp->connector_fwnode);
> +		sysfs_notify(&dp->alt->dev.kobj, "displayport", "hpd");
> +		dp->pending_hpd = false;
> +	}
>  
>  	return dp_altmode_notify(dp);
>  }
> 
> base-commit: fdf0eaf11452d72945af31804e2a1048ee1b574c
> -- 
> 2.41.0.487.g6d72f3e995-goog

-- 
heikki