[PATCH v1 1/1] usb: ulpi: defer ulpi_register on ulpi_read_id timeout

[Ferry Toth <ftoth@exalondelft.nl>]

Since commit 0f010171
Dual Role support on Intel Merrifield platform broke due to rearranging
the call to dwc3_get_extcon().

It appears to be caused by ulpi_read_id() on the first test write failing
with -ETIMEDOUT. Currently ulpi_read_id() expects to discover the phy via
DT when the test write fails and returns 0 in that case even if DT does not
provide the phy. Due to the timeout being masked dwc3 probe continues by
calling dwc3_core_soft_reset() followed by dwc3_get_extcon() which happens
to return -EPROBE_DEFER. On deferred probe ulpi_read_id() finally succeeds.

This patch changes ulpi_read_id() to return -ETIMEDOUT when it occurs and
catches the error in dwc3_core_init(). It handles the error by calling
dwc3_core_soft_reset() after which it requests -EPROBE_DEFER. On deferred
probe ulpi_read_id() again succeeds.

Signed-off-by: Ferry Toth <ftoth@exalondelft.nl>
---
 drivers/usb/common/ulpi.c | 5 +++--
 drivers/usb/dwc3/core.c   | 5 ++++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
index d7c8461976ce..d8f22bc2f9d0 100644
--- a/drivers/usb/common/ulpi.c
+++ b/drivers/usb/common/ulpi.c
@@ -206,8 +206,9 @@ static int ulpi_read_id(struct ulpi *ulpi)
 
 	/* Test the interface */
 	ret = ulpi_write(ulpi, ULPI_SCRATCH, 0xaa);
-	if (ret < 0)
-		goto err;
+	if (ret < 0) {
+		return ret;
+	}
 
 	ret = ulpi_read(ulpi, ULPI_SCRATCH);
 	if (ret < 0)
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 648f1c570021..e293ef70039b 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1106,8 +1106,11 @@ static int dwc3_core_init(struct dwc3 *dwc)
 
 	if (!dwc->ulpi_ready) {
 		ret = dwc3_core_ulpi_init(dwc);
-		if (ret)
+		if (ret) {
+			dwc3_core_soft_reset(dwc);
+			ret = -EPROBE_DEFER;
 			goto err0;
+		}
 		dwc->ulpi_ready = true;
 	}
 
-- 
2.34.1