linux-kernel - [PATCH 1/1] usb: typec: tcpci: add functions to read the VBUS voltage

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Date:   Tue,  7 May 2019 18:40:27 -0600
From:   "Angus Ainslie (Purism)" <angus@...ea.ca>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Angus Ainslie (Purism)" <angus@...ea.ca>
Subject: [PATCH 1/1] usb: typec: tcpci: add functions to read the VBUS voltage

Show an error when the VBUS voltage is out of range.

Signed-off-by: Angus Ainslie (Purism) <angus@...ea.ca>
---
 drivers/usb/typec/tcpm/tcpci.c | 35 ++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/drivers/usb/typec/tcpm/tcpci.c b/drivers/usb/typec/tcpm/tcpci.c
index a5746657b190..223941e11ef3 100644
--- a/drivers/usb/typec/tcpm/tcpci.c
+++ b/drivers/usb/typec/tcpm/tcpci.c
@@ -261,6 +261,26 @@ static int tcpci_set_pd_rx(struct tcpc_dev *tcpc, bool enable)
 	return 0;
 }
 
+static int tcpci_get_vbus_voltage(struct tcpc_dev *tcpc)
+{
+	struct tcpci *tcpci = tcpc_to_tcpci(tcpc);
+	u16 vbus_reg;
+	unsigned int vbus_voltage;
+	int ret, scale;
+
+	ret = tcpci_read16(tcpci, TCPC_VBUS_VOLTAGE, &vbus_reg);
+	if (ret < 0)
+		return ret;
+
+	vbus_voltage = vbus_reg & 0x3f;
+
+	scale = (vbus_reg >> 10) & 3;
+	if (scale == 3)
+		return -EIO;
+
+	return (vbus_voltage << scale) * 25;
+}
+
 static int tcpci_get_vbus(struct tcpc_dev *tcpc)
 {
 	struct tcpci *tcpci = tcpc_to_tcpci(tcpc);
@@ -401,6 +421,7 @@ static int tcpci_init(struct tcpc_dev *tcpc)
 irqreturn_t tcpci_irq(struct tcpci *tcpci)
 {
 	u16 status;
+	int ret;
 
 	tcpci_read16(tcpci, TCPC_ALERT, &status);
 
@@ -474,6 +495,20 @@ irqreturn_t tcpci_irq(struct tcpci *tcpci)
 		tcpci_write16(tcpci, TCPC_FAULT_STATUS, fault_status);
 	}
 
+	if (status & (TCPC_ALERT_V_ALARM_LO | TCPC_ALERT_V_ALARM_HI)) {
+		ret = tcpci_get_vbus_voltage(&tcpci->tcpc);
+
+		if (ret >= 0) {
+			if (status & TCPC_ALERT_V_ALARM_LO)
+				dev_err(tcpci->dev, "Low VBUS voltage %d mV\n",
+						ret);
+
+			if (status & TCPC_ALERT_V_ALARM_HI)
+				dev_err(tcpci->dev, "High VBUS voltage %d mV\n",
+						ret);
+		}
+	}
+
 	return IRQ_HANDLED;
 }
 EXPORT_SYMBOL_GPL(tcpci_irq);
-- 
2.17.1