[PATCH 2/2 v4] typec: tcpm: Only request matching pdos

[Badhri Jagan Sridharan <badhri@google.com>]

At present, TCPM code assumes that local device supports
variable/batt pdos and always selects the pdo with highest
possible power within the board limit. This assumption
might not hold good for all devices. To overcome this,
this patch makes TCPM only accept a source_pdo when there is
a matching sink pdo.

For Fixed pdos: The voltage should match between the
incoming source_cap and the registered snk_pdo
For Variable/Batt pdos: The incoming source_cap voltage
range should fall within the registered snk_pdo's voltage
range.

Also, when the cap_mismatch bit is set, the max_power/current
should be set to the max_current/power of the sink_pdo.
This is according to:

"If the Capability Mismatch bit is set to one
The Maximum Operating Current/Power field may contain a value
larger than the maximum current/power offered in the Source
Capabilities message’s PDO as referenced by the Object position field.
This enables the Sink to indicate that it requires more current/power
than is being offered. If the Sink requires a different voltage this
will be indicated by its Sink Capabilities message.

Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>
---
Changelog since v1:
- Rebased the patch on top of drivers/usb/type/tcpm.c
- Added duplicate pdo check for variable/batt pdo.
- Fixed tabs as suggested by dan.carpenter@oracle.com

Changelog since v2:
- Rebase

Changelog since v2:
- Refactored code fixed formatting issues as suggested
  by heikki.krogerus@linux.intel.com

 drivers/usb/typec/tcpm.c | 146 +++++++++++++++++++++++++++++++++++------------
 1 file changed, 111 insertions(+), 35 deletions(-)

diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
index ecdad71a6159..44a080202a70 100644
--- a/drivers/usb/typec/tcpm.c
+++ b/drivers/usb/typec/tcpm.c
@@ -261,6 +261,9 @@ struct tcpm_port {
 	unsigned int nr_src_pdo;
 	u32 snk_pdo[PDO_MAX_OBJECTS];
 	unsigned int nr_snk_pdo;
+	unsigned int nr_fixed; /* number of fixed sink PDOs */
+	unsigned int nr_var; /* number of variable sink PDOs */
+	unsigned int nr_batt; /* number of battery sink PDOs */
 	u32 snk_vdo[VDO_MAX_OBJECTS];
 	unsigned int nr_snk_vdo;
 
@@ -1761,39 +1764,86 @@ static int tcpm_pd_check_request(struct tcpm_port *port)
 	return 0;
 }
 
-static int tcpm_pd_select_pdo(struct tcpm_port *port)
+#define min_power(x, y) min(pdo_max_power(x), pdo_max_power(y))
+#define min_current(x, y) min(pdo_max_current(x), pdo_max_current(y))
+
+static int tcpm_pd_select_pdo(struct tcpm_port *port, int *sink_pdo)
 {
-	unsigned int i, max_mw = 0, max_mv = 0;
+	unsigned int i, j, max_mw = 0, max_mv = 0, mw = 0, mv = 0, ma = 0;
 	int ret = -EINVAL;
 
 	/*
-	 * Select the source PDO providing the most power while staying within
-	 * the board's voltage limits. Prefer PDO providing exp
+	 * Select the source PDO providing the most power which has a
+	 * matchig sink cap.
 	 */
 	for (i = 0; i < port->nr_source_caps; i++) {
 		u32 pdo = port->source_caps[i];
 		enum pd_pdo_type type = pdo_type(pdo);
-		unsigned int mv, ma, mw;
 
-		if (type == PDO_TYPE_FIXED)
-			mv = pdo_fixed_voltage(pdo);
-		else
-			mv = pdo_min_voltage(pdo);
-
-		if (type == PDO_TYPE_BATT) {
-			mw = pdo_max_power(pdo);
-		} else {
-			ma = min(pdo_max_current(pdo),
-				 port->max_snk_ma);
-			mw = ma * mv / 1000;
-		}
-
-		/* Perfer higher voltages if available */
-		if ((mw > max_mw || (mw == max_mw && mv > max_mv)) &&
-		    mv <= port->max_snk_mv) {
-			ret = i;
-			max_mw = mw;
-			max_mv = mv;
+		if (type == PDO_TYPE_FIXED) {
+			for (j = 0; j < port->nr_fixed; j++) {
+				if (pdo_fixed_voltage(pdo) ==
+				    pdo_fixed_voltage(port->snk_pdo[j])) {
+					ma = min_current(pdo, port->snk_pdo[j]);
+					mv = pdo_fixed_voltage(pdo);
+					mw = ma * mv / 1000;
+					if (mw > max_mw ||
+					    (mw == max_mw && mv > max_mv)) {
+						ret = i;
+						*sink_pdo = j;
+						max_mw = mw;
+						max_mv = mv;
+					}
+					/* There could only be one fixed pdo
+					 * at a specific voltage level.
+					 * So breaking here.
+					 */
+					break;
+				}
+			}
+		} else if (type == PDO_TYPE_BATT) {
+			for (j = port->nr_fixed;
+			     j < port->nr_fixed +
+				 port->nr_batt;
+			     j++) {
+				if (pdo_min_voltage(pdo) >=
+				     pdo_min_voltage(port->snk_pdo[j]) &&
+				     pdo_max_voltage(pdo) <=
+				     pdo_max_voltage(port->snk_pdo[j])) {
+					mw = min_power(pdo, port->snk_pdo[j]);
+					mv = pdo_min_voltage(pdo);
+					if (mw > max_mw ||
+					    (mw == max_mw && mv > max_mv)) {
+						ret = i;
+						*sink_pdo = j;
+						max_mw = mw;
+						max_mv = mv;
+					}
+				}
+			}
+		} else if (type == PDO_TYPE_VAR) {
+			for (j = port->nr_fixed +
+				 port->nr_batt;
+			     j < port->nr_fixed +
+				 port->nr_batt +
+				 port->nr_var;
+			     j++) {
+				if (pdo_min_voltage(pdo) >=
+				     pdo_min_voltage(port->snk_pdo[j]) &&
+				     pdo_max_voltage(pdo) <=
+				     pdo_max_voltage(port->snk_pdo[j])) {
+					ma = min_current(pdo, port->snk_pdo[j]);
+					mv = pdo_min_voltage(pdo);
+					mw = ma * mv / 1000;
+					if (mw > max_mw ||
+					    (mw == max_mw && mv > max_mv)) {
+						ret = i;
+						*sink_pdo = j;
+						max_mw = mw;
+						max_mv = mv;
+					}
+				}
+			}
 		}
 	}
 
@@ -1805,13 +1855,14 @@ static int tcpm_pd_build_request(struct tcpm_port *port, u32 *rdo)
 	unsigned int mv, ma, mw, flags;
 	unsigned int max_ma, max_mw;
 	enum pd_pdo_type type;
-	int index;
-	u32 pdo;
+	int index, snk_pdo_index;
+	u32 pdo, matching_snk_pdo;
 
-	index = tcpm_pd_select_pdo(port);
+	index = tcpm_pd_select_pdo(port, &snk_pdo_index);
 	if (index < 0)
 		return -EINVAL;
 	pdo = port->source_caps[index];
+	matching_snk_pdo = port->snk_pdo[snk_pdo_index];
 	type = pdo_type(pdo);
 
 	if (type == PDO_TYPE_FIXED)
@@ -1819,26 +1870,29 @@ static int tcpm_pd_build_request(struct tcpm_port *port, u32 *rdo)
 	else
 		mv = pdo_min_voltage(pdo);
 
-	/* Select maximum available current within the board's power limit */
+	/* Select maximum available current within the sink pdo's limit */
 	if (type == PDO_TYPE_BATT) {
-		mw = pdo_max_power(pdo);
-		ma = 1000 * min(mw, port->max_snk_mw) / mv;
+		mw = min(pdo_max_power(pdo), pdo_max_power(matching_snk_pdo));
+		ma = 1000 * mw / mv;
 	} else {
 		ma = min(pdo_max_current(pdo),
-			 1000 * port->max_snk_mw / mv);
+			 pdo_max_current(matching_snk_pdo));
+		mw = ma * mv / 1000;
 	}
-	ma = min(ma, port->max_snk_ma);
 
 	flags = RDO_USB_COMM | RDO_NO_SUSPEND;
 
 	/* Set mismatch bit if offered power is less than operating power */
-	mw = ma * mv / 1000;
 	max_ma = ma;
 	max_mw = mw;
 	if (mw < port->operating_snk_mw) {
 		flags |= RDO_CAP_MISMATCH;
-		max_mw = port->operating_snk_mw;
-		max_ma = max_mw * 1000 / mv;
+		if (type == PDO_TYPE_BATT &&
+		    (pdo_max_power(matching_snk_pdo) > pdo_max_power(pdo)))
+			max_mw = pdo_max_power(matching_snk_pdo);
+		else if (pdo_max_current(matching_snk_pdo) >
+			 pdo_max_current(pdo))
+			max_ma = pdo_max_current(matching_snk_pdo);
 	}
 
 	tcpm_log(port, "cc=%d cc1=%d cc2=%d vbus=%d vconn=%s polarity=%d",
@@ -3587,6 +3641,19 @@ int tcpm_update_sink_capabilities(struct tcpm_port *port, const u32 *pdo,
 }
 EXPORT_SYMBOL_GPL(tcpm_update_sink_capabilities);
 
+static int nr_type_pdos(const u32 *pdo, unsigned int nr_pdo,
+			enum pd_pdo_type type)
+{
+	int count = 0;
+	int i;
+
+	for (i = 0; i < nr_pdo; i++) {
+		if (pdo_type(pdo[i]) == type)
+			count++;
+	}
+	return count;
+}
+
 struct tcpm_port *tcpm_register_port(struct device *dev, struct tcpc_dev *tcpc)
 {
 	struct tcpm_port *port;
@@ -3632,6 +3699,15 @@ struct tcpm_port *tcpm_register_port(struct device *dev, struct tcpc_dev *tcpc)
 					  tcpc->config->nr_src_pdo);
 	port->nr_snk_pdo = tcpm_copy_pdos(port->snk_pdo, tcpc->config->snk_pdo,
 					  tcpc->config->nr_snk_pdo);
+	port->nr_fixed =  nr_type_pdos(port->snk_pdo,
+				       port->nr_snk_pdo,
+				       PDO_TYPE_FIXED);
+	port->nr_var = nr_type_pdos(port->snk_pdo,
+				    port->nr_snk_pdo,
+				    PDO_TYPE_VAR);
+	port->nr_batt = nr_type_pdos(port->snk_pdo,
+				     port->nr_snk_pdo,
+				     PDO_TYPE_BATT);
 	port->nr_snk_vdo = tcpm_copy_vdos(port->snk_vdo, tcpc->config->snk_vdo,
 					  tcpc->config->nr_snk_vdo);
 
-- 
2.15.0.403.gc27cc4dac6-goog