Re: [PATCH 2/6] usb: typec: tcpm: Move locking into tcpm_queue_vdm()

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On 7/15/20 6:22 AM, Hans de Goede wrote:
> Various callers (all the typec_altmode_ops) take the port-lock just for
> the tcpm_queue_vdm() call.
> 
> Rename the raw (unlocked) tcpm_queue_vdm() call to
> tcpm_queue_vdm_unlocked() and add a new tcpm_queue_vdm() helper which takes
> the lock, so that its callers don't have to do this themselves.
> 
> This is a preparation patch for fixing an AB BA lock inversion between the
> tcpm code and some altmode drivers.
> 
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 27 ++++++++++++++-------------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index fc6455a29c74..30e997d6ea1e 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -958,9 +958,11 @@ static void tcpm_queue_message(struct tcpm_port *port,
>  /*
>   * VDM/VDO handling functions
>   */
> -static void tcpm_queue_vdm(struct tcpm_port *port, const u32 header,
> -			   const u32 *data, int cnt)
> +static void tcpm_queue_vdm_unlocked(struct tcpm_port *port, const u32 header,
> +				    const u32 *data, int cnt)

The new function name is misleading. I think tcpm_queue_vdm_locked()
would be a much better name. Alternatively, consider keeping tcpm_queue_vdm()
as is and add tcpm_queue_vdm_unlocked().

>  {
> +	WARN_ON(!mutex_is_locked(&port->lock));
> +
>  	port->vdo_count = cnt + 1;
>  	port->vdo_data[0] = header;
>  	memcpy(&port->vdo_data[1], data, sizeof(u32) * cnt);
> @@ -971,6 +973,14 @@ static void tcpm_queue_vdm(struct tcpm_port *port, const u32 header,
>  	mod_delayed_work(port->wq, &port->vdm_state_machine, 0);
>  }
>  
> +static void tcpm_queue_vdm(struct tcpm_port *port, const u32 header,
> +			   const u32 *data, int cnt)
> +{
> +	mutex_lock(&port->lock);
> +	tcpm_queue_vdm_unlocked(port, header, data, cnt);
> +	mutex_unlock(&port->lock);
> +}
> +
>  static void svdm_consume_identity(struct tcpm_port *port, const __le32 *payload,
>  				  int cnt)
>  {
> @@ -1249,7 +1259,7 @@ static void tcpm_handle_vdm_request(struct tcpm_port *port,
>  		rlen = tcpm_pd_svdm(port, payload, cnt, response);
>  
>  	if (rlen > 0)
> -		tcpm_queue_vdm(port, response[0], &response[1], rlen - 1);
> +		tcpm_queue_vdm_unlocked(port, response[0], &response[1], rlen - 1);
>  }
>  
>  static void tcpm_send_vdm(struct tcpm_port *port, u32 vid, int cmd,
> @@ -1263,7 +1273,7 @@ static void tcpm_send_vdm(struct tcpm_port *port, u32 vid, int cmd,
>  	/* set VDM header with VID & CMD */
>  	header = VDO(vid, ((vid & USB_SID_PD) == USB_SID_PD) ?
>  			1 : (PD_VDO_CMD(cmd) <= CMD_ATTENTION), cmd);
> -	tcpm_queue_vdm(port, header, data, count);
> +	tcpm_queue_vdm_unlocked(port, header, data, count);
>  }
>  
>  static unsigned int vdm_ready_timeout(u32 vdm_hdr)
> @@ -1506,13 +1516,10 @@ static int tcpm_altmode_enter(struct typec_altmode *altmode, u32 *vdo)
>  	struct tcpm_port *port = typec_altmode_get_drvdata(altmode);
>  	u32 header;
>  
> -	mutex_lock(&port->lock);
>  	header = VDO(altmode->svid, vdo ? 2 : 1, CMD_ENTER_MODE);
>  	header |= VDO_OPOS(altmode->mode);
>  
>  	tcpm_queue_vdm(port, header, vdo, vdo ? 1 : 0);
> -	mutex_unlock(&port->lock);
> -
>  	return 0;
>  }
>  
> @@ -1521,13 +1528,10 @@ static int tcpm_altmode_exit(struct typec_altmode *altmode)
>  	struct tcpm_port *port = typec_altmode_get_drvdata(altmode);
>  	u32 header;
>  
> -	mutex_lock(&port->lock);
>  	header = VDO(altmode->svid, 1, CMD_EXIT_MODE);
>  	header |= VDO_OPOS(altmode->mode);
>  
>  	tcpm_queue_vdm(port, header, NULL, 0);
> -	mutex_unlock(&port->lock);
> -
>  	return 0;
>  }
>  
> @@ -1536,10 +1540,7 @@ static int tcpm_altmode_vdm(struct typec_altmode *altmode,
>  {
>  	struct tcpm_port *port = typec_altmode_get_drvdata(altmode);
>  
> -	mutex_lock(&port->lock);
>  	tcpm_queue_vdm(port, header, data, count - 1);
> -	mutex_unlock(&port->lock);
> -
>  	return 0;
>  }
>  
> 




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