linux-kernel - [PATCH v1 1/1] usb: ulpi: defer ulpi_register on ulpi_read

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Message-Id: <20221109221749.8210-1-ftoth@exalondelft.nl>
Date:   Wed,  9 Nov 2022 23:17:49 +0100
From:   Ferry Toth <ftoth@...londelft.nl>
To:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Sean Anderson <sean.anderson@...o.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Stephen Boyd <stephen.boyd@...aro.org>,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Ferry Toth <ftoth@...londelft.nl>
Subject: [PATCH v1 1/1] usb: ulpi: defer ulpi_register on ulpi_read_id timeout

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@...londelft.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