linux-kernel - [PATCH 3.16 167/305] usb: dwc3: exynos: Fix deferred probing storm.

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Message-ID: <lsq.1471110171.574352701@decadent.org.uk>
Date:	Sat, 13 Aug 2016 18:42:51 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Vivek Gautam" <gautam.vivek@...sung.com>,
	"Steinar H. Gunderson" <sesse@...gle.com>,
	"Felipe Balbi" <felipe.balbi@...ux.intel.com>,
	"Krzysztof Kozlowski" <k.kozlowski@...sung.com>
Subject: [PATCH 3.16 167/305] usb: dwc3: exynos: Fix deferred probing storm.

3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Steinar H. Gunderson" <sesse@...gle.com>

commit 4879efb34f7d49235fac334d76d9c6a77a021413 upstream.

dwc3-exynos has two problems during init if the regulators are slow
to come up (for instance if the I2C bus driver is not on the initramfs)
and return probe deferral. First, every time this happens, the driver
leaks the USB phys created; they need to be deallocated on error.

Second, since the phy devices are created before the regulators fail,
this means that there's a new device to re-trigger deferred probing,
which causes it to essentially go into a busy loop of re-probing the
device until the regulators come up.

Move the phy creation to after the regulators have succeeded, and also
fix cleanup on failure. On my ODROID XU4 system (with Debian's initramfs
which doesn't contain the I2C driver), this reduces the number of probe
attempts (for each of the two controllers) from more than 2000 to eight.

Signed-off-by: Steinar H. Gunderson <sesse@...gle.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
Reviewed-by: Vivek Gautam <gautam.vivek@...sung.com>
Fixes: d720f057fda4 ("usb: dwc3: exynos: add nop transceiver support")
Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/dwc3/dwc3-exynos.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

--- a/drivers/usb/dwc3/dwc3-exynos.c
+++ b/drivers/usb/dwc3/dwc3-exynos.c
@@ -129,12 +129,6 @@ static int dwc3_exynos_probe(struct plat

 	platform_set_drvdata(pdev, exynos);

-	ret = dwc3_exynos_register_phys(exynos);
-	if (ret) {
-		dev_err(dev, "couldn't register PHYs\n");
-		return ret;
-	}
-
 	clk = devm_clk_get(dev, "usbdrd30");
 	if (IS_ERR(clk)) {
 		dev_err(dev, "couldn't get clock\n");
@@ -168,20 +162,29 @@ static int dwc3_exynos_probe(struct plat
 		goto err3;
 	}

+	ret = dwc3_exynos_register_phys(exynos);
+	if (ret) {
+		dev_err(dev, "couldn't register PHYs\n");
+		goto err4;
+	}
+
 	if (node) {
 		ret = of_platform_populate(node, NULL, NULL, dev);
 		if (ret) {
 			dev_err(dev, "failed to add dwc3 core\n");
-			goto err4;
+			goto err5;
 		}
 	} else {
 		dev_err(dev, "no device node, failed to add dwc3 core\n");
 		ret = -ENODEV;
-		goto err4;
+		goto err5;
 	}

 	return 0;

+err5:
+	platform_device_unregister(exynos->usb2_phy);
+	platform_device_unregister(exynos->usb3_phy);
 err4:
 	regulator_disable(exynos->vdd10);
 err3: