linux-kernel - Re: [PATCH 2/3] usb: typec: ucsi: Never send a lone connector change ack

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Message-ID: <Zg0yAfuhoOT0XrX+@kuha.fi.intel.com>
Date: Wed, 3 Apr 2024 13:40:01 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: "Christian A. Ehrhardt" <lk@...e.de>
Cc: linux-kernel@...r.kernel.org,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Prashant Malani <pmalani@...omium.org>,
	Jameson Thies <jthies@...gle.com>,
	Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	Samuel Čavoj <samuel@...oj.net>,
	linux-usb@...r.kernel.org
Subject: Re: [PATCH 2/3] usb: typec: ucsi: Never send a lone connector change
 ack

On Wed, Mar 27, 2024 at 11:45:53PM +0100, Christian A. Ehrhardt wrote:
> Some PPM implementation do not like UCSI_ACK_CONNECTOR_CHANGE
> without UCSI_ACK_COMMAND_COMPLETE. Moreover, doing this is racy
> as it requires sending two UCSI_ACK_CC_CI commands in a row and
> the second one will be started with UCSI_CCI_ACK_COMPLETE already
> set in CCI.
> 
> Bundle the UCSI_ACK_CONNECTOR_CHANGE with the UCSI_ACK_COMMAND_COMPLETE
> for the UCSI_GET_CONNECTOR_STATUS command that is sent while
> handling a connector change event.
> 
> Signed-off-by: Christian A. Ehrhardt <lk@...e.de>

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

> ---
>  drivers/usb/typec/ucsi/ucsi.c | 48 +++++++++++++++--------------------
>  1 file changed, 21 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index 31d8a46ae5e7..48f093a1dc09 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -49,22 +49,16 @@ static int ucsi_read_message_in(struct ucsi *ucsi, void *buf,
>  	return ucsi->ops->read(ucsi, UCSI_MESSAGE_IN, buf, buf_size);
>  }
>  
> -static int ucsi_acknowledge_command(struct ucsi *ucsi)
> +static int ucsi_acknowledge(struct ucsi *ucsi, bool conn_ack)
>  {
>  	u64 ctrl;
>  
>  	ctrl = UCSI_ACK_CC_CI;
>  	ctrl |= UCSI_ACK_COMMAND_COMPLETE;
> -
> -	return ucsi->ops->sync_write(ucsi, UCSI_CONTROL, &ctrl, sizeof(ctrl));
> -}
> -
> -static int ucsi_acknowledge_connector_change(struct ucsi *ucsi)
> -{
> -	u64 ctrl;
> -
> -	ctrl = UCSI_ACK_CC_CI;
> -	ctrl |= UCSI_ACK_CONNECTOR_CHANGE;
> +	if (conn_ack) {
> +		clear_bit(EVENT_PENDING, &ucsi->flags);
> +		ctrl |= UCSI_ACK_CONNECTOR_CHANGE;
> +	}
>  
>  	return ucsi->ops->sync_write(ucsi, UCSI_CONTROL, &ctrl, sizeof(ctrl));
>  }
> @@ -77,7 +71,7 @@ static int ucsi_read_error(struct ucsi *ucsi)
>  	int ret;
>  
>  	/* Acknowledge the command that failed */
> -	ret = ucsi_acknowledge_command(ucsi);
> +	ret = ucsi_acknowledge(ucsi, false);
>  	if (ret)
>  		return ret;
>  
> @@ -89,7 +83,7 @@ static int ucsi_read_error(struct ucsi *ucsi)
>  	if (ret)
>  		return ret;
>  
> -	ret = ucsi_acknowledge_command(ucsi);
> +	ret = ucsi_acknowledge(ucsi, false);
>  	if (ret)
>  		return ret;
>  
> @@ -152,7 +146,7 @@ static int ucsi_exec_command(struct ucsi *ucsi, u64 cmd)
>  		return -EIO;
>  
>  	if (cci & UCSI_CCI_NOT_SUPPORTED) {
> -		if (ucsi_acknowledge_command(ucsi) < 0)
> +		if (ucsi_acknowledge(ucsi, false) < 0)
>  			dev_err(ucsi->dev,
>  				"ACK of unsupported command failed\n");
>  		return -EOPNOTSUPP;
> @@ -165,15 +159,15 @@ static int ucsi_exec_command(struct ucsi *ucsi, u64 cmd)
>  	}
>  
>  	if (cmd == UCSI_CANCEL && cci & UCSI_CCI_CANCEL_COMPLETE) {
> -		ret = ucsi_acknowledge_command(ucsi);
> +		ret = ucsi_acknowledge(ucsi, false);
>  		return ret ? ret : -EBUSY;
>  	}
>  
>  	return UCSI_CCI_LENGTH(cci);
>  }
>  
> -int ucsi_send_command(struct ucsi *ucsi, u64 command,
> -		      void *data, size_t size)
> +static int ucsi_send_command_common(struct ucsi *ucsi, u64 command,
> +				    void *data, size_t size, bool conn_ack)
>  {
>  	u8 length;
>  	int ret;
> @@ -192,7 +186,7 @@ int ucsi_send_command(struct ucsi *ucsi, u64 command,
>  			goto out;
>  	}
>  
> -	ret = ucsi_acknowledge_command(ucsi);
> +	ret = ucsi_acknowledge(ucsi, conn_ack);
>  	if (ret)
>  		goto out;
>  
> @@ -201,6 +195,12 @@ int ucsi_send_command(struct ucsi *ucsi, u64 command,
>  	mutex_unlock(&ucsi->ppm_lock);
>  	return ret;
>  }
> +
> +int ucsi_send_command(struct ucsi *ucsi, u64 command,
> +		      void *data, size_t size)
> +{
> +	return ucsi_send_command_common(ucsi, command, data, size, false);
> +}
>  EXPORT_SYMBOL_GPL(ucsi_send_command);
>  
>  /* -------------------------------------------------------------------------- */
> @@ -1168,7 +1168,9 @@ static void ucsi_handle_connector_change(struct work_struct *work)
>  	mutex_lock(&con->lock);
>  
>  	command = UCSI_GET_CONNECTOR_STATUS | UCSI_CONNECTOR_NUMBER(con->num);
> -	ret = ucsi_send_command(ucsi, command, &con->status, sizeof(con->status));
> +
> +	ret = ucsi_send_command_common(ucsi, command, &con->status,
> +				       sizeof(con->status), true);
>  	if (ret < 0) {
>  		dev_err(ucsi->dev, "%s: GET_CONNECTOR_STATUS failed (%d)\n",
>  			__func__, ret);
> @@ -1225,14 +1227,6 @@ static void ucsi_handle_connector_change(struct work_struct *work)
>  	if (con->status.change & UCSI_CONSTAT_CAM_CHANGE)
>  		ucsi_partner_task(con, ucsi_check_altmodes, 1, 0);
>  
> -	mutex_lock(&ucsi->ppm_lock);
> -	clear_bit(EVENT_PENDING, &con->ucsi->flags);
> -	ret = ucsi_acknowledge_connector_change(ucsi);
> -	mutex_unlock(&ucsi->ppm_lock);
> -
> -	if (ret)
> -		dev_err(ucsi->dev, "%s: ACK failed (%d)", __func__, ret);
> -
>  out_unlock:
>  	mutex_unlock(&con->lock);
>  }
> -- 
> 2.40.1

-- 
heikki