On 10/28/2016 04:56 AM, David Lechner wrote:
> On 10/26/2016 05:58 AM, Alexandre Bailon wrote:
>> When the phy is forced in host mode, only the first hot plug and
>> hot remove works. That is actually because the driver execute the
>> OTG workaround, whereas it is not applicable in host or device mode.
>> Indeed, to work correctly, the VBUS sense and session end comparator
>> must be enabled, what is only possible when the phy is in OTG mode.
>> Only execute the workaround if the phy is in OTG mode.
>>
>> Signed-off-by: Alexandre Bailon <abailon@xxxxxxxxxxxx>
>> ---
>> drivers/usb/musb/da8xx.c | 11 +++++++++++
>> 1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/usb/musb/da8xx.c b/drivers/usb/musb/da8xx.c
>> index 6749aa1..b8a6b65 100644
>> --- a/drivers/usb/musb/da8xx.c
>> +++ b/drivers/usb/musb/da8xx.c
>> @@ -145,6 +145,17 @@ static void otg_timer(unsigned long _musb)
>> unsigned long flags;
>>
>> /*
>> + * We should only execute the OTG workaround when the phy is in OTG
>> + * mode. The workaround require the VBUS sense and the session end
>> + * comparator to be enabled, what is only possible if the phy is in
>> + * OTG mode. As the workaround is only required to detect if the
>> + * controller must act as host or device, we can safely exit OTG is
>> + * not in use.
>> + */
>> + if (musb->port_mode != MUSB_PORT_MODE_DUAL_ROLE)
>
> musb->port_mode is not valid if we have changed the mode via sysfs. It
> only reflects the mode set during driver probe.
>
> Furthermore, this breaks the host mode completely for me. The first hot
> plug is not even detected.
>
>> + return;
>> +
>> + /*
>> * We poll because DaVinci's won't expose several OTG-critical
>> * status change events (from the transceiver) otherwise.
>> */
>>
>
>
> The way this is working for me (on AM1808) is this:
>
> The problem is not that the OTG workaround is being used. The problem is
> that after disconnect, the VBUSDRV is turned off. If you look at the
> handler for DA8XX_INTR_DRVVBUS in da8xx_musb_interrupt(), you will see
> that if VBUSDRV is off, then drvvbus == 0, which puts the musb state
> back to device mode.
>
> I also ran into a similar problem a while back[1] that if you use a
> self-powered device in host mode, it immediately becomes disconnected.
> This is for the exact same reason. When a port detects a self-powered
> device, it turns of VBUSDRV, which triggers the DA8XX_INTR_DRVVBUS
> interrupt. As we have seen above, this takes the port out of host mode.
>
> The workaround that I have found that seems to fix both cases is to add
> and else if statement that toggles the PHY host override when we are
> forcing host mode and the VBUSDRV is turned off.
I like this workaround.
>
> Here is a partial diff of drivers/usb/musb/da8xx.c to show what I mean:
>
> @@ -304,10 +309,14 @@ static irqreturn_t da8xx_musb_interrupt(int irq,
> void *hci)
> * Also, DRVVBUS pulses for SRP (but not at 5 V)...
> */
> if (status & (DA8XX_INTR_DRVVBUS << DA8XX_INTR_USB_SHIFT)) {
> + struct da8xx_glue *glue =
> + dev_get_drvdata(musb->controller->parent);
> int drvvbus = musb_readl(reg_base, DA8XX_USB_STAT_REG);
> void __iomem *mregs = musb->mregs;
> u8 devctl = musb_readb(mregs, MUSB_DEVCTL);
> - int err;
> + int cfgchip2, err;
> +
> + regmap_read(glue->cfgchip, CFGCHIP(2), &cfgchip2);
>
> err = musb->int_usb & MUSB_INTR_VBUSERROR;
> if (err) {
> @@ -332,10 +341,25 @@ static irqreturn_t da8xx_musb_interrupt(int irq,
> void *hci)
> musb->xceiv->otg->state = OTG_STATE_A_WAIT_VRISE;
> portstate(musb->port1_status |=
> USB_PORT_STAT_POWER);
> del_timer(&otg_workaround);
> + } else if ((cfgchip2 & CFGCHIP2_OTGMODE_MASK)
> + == CFGCHIP2_OTGMODE_FORCE_HOST) {
> + /*
> + * If we are forcing host mode, VBUSDRV is
> turned off
> + * after a device is disconnected. We need to
> toggle the
> + * VBUS/ID override to trigger turn it back on,
> which
> + * has the effect of triggering
> DA8XX_INTR_DRVVBUS again.
> + */
> + regmap_write_bits(glue->cfgchip, CFGCHIP(2),
> + CFGCHIP2_OTGMODE_MASK,
> + CFGCHIP2_OTGMODE_NO_OVERRIDE);
> + regmap_write_bits(glue->cfgchip, CFGCHIP(2),
> + CFGCHIP2_OTGMODE_MASK,
> + CFGCHIP2_OTGMODE_FORCE_HOST);
> } else {
> musb->is_active = 0;
> MUSB_DEV_MODE(musb);
>
I haven't thought to this workaround.
Actually, my goal with this patch was to prevent VBUSDRV to be turned
off. When I hit the issues, I captured some traces and these traces
let think VBUSDRV is turned off when the OTG workaround clear
the bit MUSB_DEVCTL_SESSION.
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
