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

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On 5/7/19 5:40 PM, Angus Ainslie (Purism) wrote:
Show an error when the VBUS voltage is out of range.

Signed-off-by: Angus Ainslie (Purism) <angus@xxxxxxxx>
---
  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);
+
Extra empty line.

+		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);
+		}

This doesn't report anything if reading the VBUS voltage
returns an error.

Also, per TCPCI specification, you probably want to check
POWER_CONTROL.VBUS_VOLTAGE Monitor to see if it is enabled
in the first place.

On a higher level, the driver doesn't currently set limits for low
and high voltage alarms, and it doesn't enable those alarms. As such,
I wonder if/how you can get those alerts. Can you clarify ?

Thanks,
Guenter

+	}
+
  	return IRQ_HANDLED;
  }
  EXPORT_SYMBOL_GPL(tcpci_irq);





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