linux-kernel - Re: [PATCH v2 1/2] usb: typec: Add USB Power Delivery sink port support

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Date:	Wed, 27 Jul 2016 11:13:43 +0300
From:	Felipe Balbi <felipe.balbi@...ux.intel.com>
To:	Bin Gao <bin.gao@...ux.intel.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Bin Gao <bin.gao@...el.com>,
	Chandra Sekhar Anagani <chandra.sekhar.anagani@...el.com>,
	Pranav Tipnis <pranav.tipnis@...el.com>
Subject: Re: [PATCH v2 1/2] usb: typec: Add USB Power Delivery sink port support


Hi,

Bin Gao <bin.gao@...ux.intel.com> writes:
> This patch implements a simple USB Power Delivery sink port state machine.
> It assumes the hardware only handles PD packet transmitting and receiving
> over the CC line of the USB Type-C connector. The state transition is
> completely controlled by software. This patch only implement the sink port
> function and it doesn't support source port and port swap yet.
>
> This patch depends on these two patches:
> https://lkml.org/lkml/2016/6/29/349
> https://lkml.org/lkml/2016/6/29/350
>
> Signed-off-by: Bin Gao <bin.gao@...el.com>
> Changes in v2:
>  - Removed work queue so messages are directly handled in phy driver's interrupt context
>  - used pr_debug instead of pr_info for message dump
>  - Converted PD driver to tristate and typec driver is independent of it

this should be after the tearline (---) below. We don't want this in
changelog ;-)

> +static void handle_source_cap(struct pd_sink_port *port, u8 msg_revision,
> +						u8 nr_objs, u8 *buf)
> +{
> +	int i;
> +	u32 *obj;
> +	u8 type;
> +	struct pd_source_cap *cap = port->source_caps;
> +
> +	/*
> +	 * The PD spec revision included in SOURCE_CAPABILITY message is the
> +	 * highest revision that the Source supports.
> +	 */
> +	port->pd_rev = msg_revision;
> +
> +	/*
> +	 * First we need to save all PDOs - they may be used in the future.
> +	 * USB PD spec says we must use PDOs in the most recent
> +	 * SOURCE_CAPABILITY message. Here we replace old PDOs with new ones.
> +	 */
> +	port->nr_source_caps = 0;
> +	for (i = 0; i < nr_objs; i++) {
> +		obj = (u32 *)(buf + i * PD_OBJ_SIZE);
> +		type = (*obj >> SOURCE_CAP_TYPE_BIT) & SOURCE_CAP_TYPE_MASK;
> +		switch (type) {
> +		case PS_TYPE_FIXED:
> +			cap->ps_type = PS_TYPE_FIXED;
> +			cap->fixed = *(struct pd_pdo_src_fixed *)obj;
> +			break;
> +		case PS_TYPE_VARIABLE:
> +			cap->ps_type = PS_TYPE_VARIABLE;
> +			cap->variable = *(struct pd_pdo_variable *)obj;
> +			break;
> +		case PS_TYPE_BATTERY:
> +			cap->ps_type = PS_TYPE_BATTERY;
> +			cap->battery = *(struct pd_pdo_battery *)obj;
> +			break;
> +		default: /* shouldn't come here */
> +			pr_err("Invalid Source Capability type: %u.\n", type);
> +			continue;
> +		}
> +		port->nr_source_caps++;
> +		cap++;
> +	}
> +
> +	if (port->nr_source_caps == 0) {
> +		pr_err("There is no valid PDOs in SOURCE_CAPABILITY message\n");
> +		return;
> +	}
> +
> +	/* If a contract is not established, we need send a REQUEST message */
> +	if (port->state == PD_SINK_STATE_WAIT_FOR_SRC_CAP) {

this is wrong. Read the fluxchart in figure 8-42. Source can decide to
send another Source Capability before receiving our Good CRC and we need
to work with that. This state check is, at a minimum, wrong. I'd
actually just go ahead and remove it.

> +		if (!send_request(port))
> +			port->state = PD_SINK_STATE_REQUEST_SENT;
> +	}
> +}

-- 
balbi

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