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SubjectRe: [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@akkea.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);
> +
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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