[PATCH v2 2/2] usb: dwc3: Add role switch reset quirk for Apple DWC3

Sven Peter
2021-11-08T17:10:11Z

As mad as it sounds, the dwc3 controller present on Apple SoCs must be
reset and reinitialized whenever a device is unplugged from the root port
and triggers a role switch notification from the USB PD controller.

This is required for at least two reasons:

- The USB2 D+/D- lines are connected through a stateful eUSB2 repeater
which in turn is controlled by a variant of the TI TPS6598x USB PD
chip. When the USB PD controller detects a hotplug event it resets
the eUSB2 repeater. Afterwards, no new device is recognized before
the DWC3 core and PHY are reset as well.

- It's possible to completely break the dwc3 controller by switching
it to device mode and unplugging the cable at just the wrong time.
Even a CORESOFTRESET is not enough to allow new devices again.
The only workaround is to trigger a hard reset of the entire
dwc3 core. This also happens when running macOS on these
machines.

Signed-off-by: Sven Peter <sven@svenpeter.dev>
---
v1 -> v2:
- enable the quirk based on the compatible instead of a property
as requested by robh

drivers/usb/dwc3/core.c | 39 ++++++++++++++++++++++++++++++++++++---
drivers/usb/dwc3/core.h | 6 ++++++
drivers/usb/dwc3/drd.c | 7 +++++++
3 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 0104a80b185e..b76d7536eafe 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -115,6 +115,8 @@ void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode)
}

static int dwc3_core_soft_reset(struct dwc3 *dwc);
+static void dwc3_core_exit(struct dwc3 *dwc);
+static int dwc3_core_init_for_resume(struct dwc3 *dwc);

static void __dwc3_set_mode(struct work_struct *work)
{
@@ -130,10 +132,11 @@ static void __dwc3_set_mode(struct work_struct *work)
if (dwc->current_dr_role == DWC3_GCTL_PRTCAP_OTG)
dwc3_otg_update(dwc, 0);

- if (!dwc->desired_dr_role)
+ if (!dwc->desired_dr_role && !dwc->role_switch_reset_quirk)
goto out;

- if (dwc->desired_dr_role == dwc->current_dr_role)
+ if (dwc->desired_dr_role == dwc->current_dr_role &&
+ !dwc->role_switch_reset_quirk)
goto out;

if (dwc->desired_dr_role == DWC3_GCTL_PRTCAP_OTG && dwc->edev)
@@ -158,6 +161,34 @@ static void __dwc3_set_mode(struct work_struct *work)
break;
}

+ if (dwc->role_switch_reset_quirk) {
+ if (dwc->current_dr_role) {
+ dwc->current_dr_role = 0;
+ dwc3_core_exit(dwc);
+ }
+
+ if (dwc->desired_dr_role) {
+ /*
+ * the first call to __dwc3_set_mode comes from
+ * dwc3_drd_init. In that case dwc3_core_init has been
+ * called but dwc->current_dr_role is zero such that
+ * we must not reinitialize the core again here.
+ */
+ if (dwc->role_switch_reset_quirk_initialized) {
+ ret = dwc3_core_init_for_resume(dwc);
+ if (ret) {
+ dev_err(dwc->dev,
+ "failed to reinitialize core\n");
+ goto out;
+ }
+ }
+
+ dwc->role_switch_reset_quirk_initialized = 1;
+ } else {
+ goto out;
+ }
+ }
+
/* For DRD host or device mode only */
if (dwc->desired_dr_role != DWC3_GCTL_PRTCAP_OTG) {
reg = dwc3_readl(dwc->regs, DWC3_GCTL);
@@ -1586,6 +1617,8 @@ static int dwc3_probe(struct platform_device *pdev)
else
dwc->num_clks = ret;

+ if (of_device_is_compatible(dev->of_node, "apple,dwc3"))
+ dwc->role_switch_reset_quirk = true;
}

ret = reset_control_deassert(dwc->reset);
@@ -1715,7 +1748,6 @@ static int dwc3_remove(struct platform_device *pdev)
return 0;
}

-#ifdef CONFIG_PM
static int dwc3_core_init_for_resume(struct dwc3 *dwc)
{
int ret;
@@ -1742,6 +1774,7 @@ static int dwc3_core_init_for_resume(struct dwc3 *dwc)
return ret;
}

+#ifdef CONFIG_PM
static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
{
unsigned long flags;
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 5612bfdf37da..3fc5c5bc4c57 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -1080,6 +1080,9 @@ struct dwc3_scratchpad_array {
* 3 - Reserved
* @dis_metastability_quirk: set to disable metastability quirk.
* @dis_split_quirk: set to disable split boundary.
+ * @role_switch_reset_quirk: set to force reinitialization after any role switch
+ * @role_switch_reset_quirk_initialized: set to true after the first role switch
+ * which is triggered from dwc3_drd_init directly
* @imod_interval: set the interrupt moderation interval in 250ns
* increments or 0 to disable.
* @max_cfg_eps: current max number of IN eps used across all USB configs.
@@ -1291,6 +1294,9 @@ struct dwc3 {
unsigned dis_split_quirk:1;
unsigned async_callbacks:1;

+ unsigned role_switch_reset_quirk:1;
+ unsigned role_switch_reset_quirk_initialized:1;
+
u16 imod_interval;

int max_cfg_eps;
diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
index d7f76835137f..403e88a72f0e 100644
--- a/drivers/usb/dwc3/drd.c
+++ b/drivers/usb/dwc3/drd.c
@@ -506,6 +506,9 @@ static int dwc3_usb_role_switch_set(struct usb_role_switch *sw,
break;
}

+ if (dwc->role_switch_reset_quirk && role == USB_ROLE_NONE)
+ mode = 0;
+
dwc3_set_mode(dwc, mode);
return 0;
}
@@ -534,6 +537,10 @@ static enum usb_role dwc3_usb_role_switch_get(struct usb_role_switch *sw)
role = USB_ROLE_DEVICE;
break;
}
+
+ if (dwc->role_switch_reset_quirk && !dwc->current_dr_role)
+ role = USB_ROLE_NONE;
+
spin_unlock_irqrestore(&dwc->lock, flags);
return role;
}
--
2.25.1