linux-kernel - [PATCH v4 2/2] usb: dwc3: core: defer probe on ulpi_read

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Message-Id: <20221120153704.9090-3-ftoth@exalondelft.nl>
Date:   Sun, 20 Nov 2022 16:37:04 +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>,
        Ferry Toth <fntoth@...il.com>,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Ferry Toth <ftoth@...londelft.nl>, stable@...r.kernel.org
Subject: [PATCH v4 2/2] usb: dwc3: core: defer probe on ulpi_read_id timeout

Since commit 0f0101719138 ("usb: dwc3: Don't switch OTG -> peripheral if extcon is present"),
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() masking the timeout on the first
test write. In the past dwc3 probe continued by calling dwc3_core_soft_reset()
followed by dwc3_get_extcon() which happend to return -EPROBE_DEFER.
On deferred probe ulpi_read_id() finally succeeded. Due to above mentioned
rearranging -EPROBE_DEFER is not returned and probe completes without phy.

As we now changed ulpi_read_id() to return -ETIMEDOUT in this case, we
need to handle the error by calling dwc3_core_soft_reset() and request
-EPROBE_DEFER. On deferred probe ulpi_read_id() is retried and succeeds.

Fixes: ef6a7bcfb01c ("usb: ulpi: Support device discovery via DT")
Cc: stable@...r.kernel.org

Signed-off-by: Ferry Toth <ftoth@...londelft.nl>
---
 drivers/usb/dwc3/core.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 648f1c570021..2779f17bffaf 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1106,8 +1106,13 @@ static int dwc3_core_init(struct dwc3 *dwc)
 
 	if (!dwc->ulpi_ready) {
 		ret = dwc3_core_ulpi_init(dwc);
-		if (ret)
+		if (ret) {
+			if (ret == -ETIMEDOUT) {
+				dwc3_core_soft_reset(dwc);
+				ret = -EPROBE_DEFER;
+			}
 			goto err0;
+		}
 		dwc->ulpi_ready = true;
 	}
 
-- 
2.37.2