[PATCH v5] usb: exynos: add workaround for the USB device bindings conflict

[Marek Szyprowski <m.szyprowski@samsung.com>]

Commit 69bec7259853 ("USB: core: let USB device know device node") added
support for attaching devicetree node for USB devices. Those nodes are
children of their USB host controller. However Exynos EHCI and OHCI
driver bindings already define child-nodes for each physical root hub
port and assigns respective PHY controller and parameters to them. Those
bindings predates support for USB device tree nodes.

To mitigate the side-effects of the conflict between those bindings,
lets reset Exynos host controller of_node pointer before registering it
to USB subsystem. This fixes the issue raised by the commit 01fdf179f4b0
("usb: core: skip interfaces disabled in devicetree"), which incorrectly
disabled some devices on Exynos based boards.

Reported-by: Markus Reichl <m.reichl@fivetechno.de>
Suggested-by: Måns Rullgård <mans@mansr.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
v5:
- fixed error path handling as pointed by Alan

v4: https://patchwork.kernel.org/patch/10947773/
- moved workaround to Exynos OHCI/EHCI drivers as suggested by Måns

v3: https://lkml.org/lkml/2019/5/9/119
- replaced ad hoc checks by proper test for proper value of the
  compatible string in drivers/usb/core/of.c

v2: https://lkml.org/lkml/2019/5/8/321

v1: https://lkml.org/lkml/2019/5/7/715
---
 drivers/usb/host/ehci-exynos.c | 11 +++++++++++
 drivers/usb/host/ohci-exynos.c | 11 +++++++++++
 2 files changed, 22 insertions(+)

diff --git a/drivers/usb/host/ehci-exynos.c b/drivers/usb/host/ehci-exynos.c
index 8e3bab1e0c1f..3a29a1a8519c 100644
--- a/drivers/usb/host/ehci-exynos.c
+++ b/drivers/usb/host/ehci-exynos.c
@@ -39,6 +39,7 @@ static struct hc_driver __read_mostly exynos_ehci_hc_driver;
 
 struct exynos_ehci_hcd {
 	struct clk *clk;
+	struct device_node *of_node;
 	struct phy *phy[PHY_NUMBER];
 };
 
@@ -203,6 +204,13 @@ static int exynos_ehci_probe(struct platform_device *pdev)
 	ehci = hcd_to_ehci(hcd);
 	ehci->caps = hcd->regs;
 
+	/*
+	 * Workaround: reset of_node pointer to avoid conflict between Exynos
+	 * EHCI port subnodes and generic USB device bindings
+	 */
+	exynos_ehci->of_node = pdev->dev.of_node;
+	pdev->dev.of_node = NULL;
+
 	/* DMA burst Enable */
 	writel(EHCI_INSNREG00_ENABLE_DMA_BURST, EHCI_INSNREG00(hcd->regs));
 
@@ -219,6 +227,7 @@ static int exynos_ehci_probe(struct platform_device *pdev)
 
 fail_add_hcd:
 	exynos_ehci_phy_disable(&pdev->dev);
+	pdev->dev.of_node = exynos_ehci->of_node;
 fail_io:
 	clk_disable_unprepare(exynos_ehci->clk);
 fail_clk:
@@ -231,6 +240,8 @@ static int exynos_ehci_remove(struct platform_device *pdev)
 	struct usb_hcd *hcd = platform_get_drvdata(pdev);
 	struct exynos_ehci_hcd *exynos_ehci = to_exynos_ehci(hcd);
 
+	pdev->dev.of_node = exynos_ehci->of_node;
+
 	usb_remove_hcd(hcd);
 
 	exynos_ehci_phy_disable(&pdev->dev);
diff --git a/drivers/usb/host/ohci-exynos.c b/drivers/usb/host/ohci-exynos.c
index c0c4dcca6f3c..905c6317e0c3 100644
--- a/drivers/usb/host/ohci-exynos.c
+++ b/drivers/usb/host/ohci-exynos.c
@@ -30,6 +30,7 @@ static struct hc_driver __read_mostly exynos_ohci_hc_driver;
 
 struct exynos_ohci_hcd {
 	struct clk *clk;
+	struct device_node *of_node;
 	struct phy *phy[PHY_NUMBER];
 };
 
@@ -170,6 +171,13 @@ static int exynos_ohci_probe(struct platform_device *pdev)
 		goto fail_io;
 	}
 
+	/*
+	 * Workaround: reset of_node pointer to avoid conflict between Exynos
+	 * OHCI port subnodes and generic USB device bindings
+	 */
+	exynos_ohci->of_node = pdev->dev.of_node;
+	pdev->dev.of_node = NULL;
+
 	err = usb_add_hcd(hcd, irq, IRQF_SHARED);
 	if (err) {
 		dev_err(&pdev->dev, "Failed to add USB HCD\n");
@@ -180,6 +188,7 @@ static int exynos_ohci_probe(struct platform_device *pdev)
 
 fail_add_hcd:
 	exynos_ohci_phy_disable(&pdev->dev);
+	pdev->dev.of_node = exynos_ohci->of_node;
 fail_io:
 	clk_disable_unprepare(exynos_ohci->clk);
 fail_clk:
@@ -192,6 +201,8 @@ static int exynos_ohci_remove(struct platform_device *pdev)
 	struct usb_hcd *hcd = platform_get_drvdata(pdev);
 	struct exynos_ohci_hcd *exynos_ohci = to_exynos_ohci(hcd);
 
+	pdev->dev.of_node = exynos_ohci->of_node;
+
 	usb_remove_hcd(hcd);
 
 	exynos_ohci_phy_disable(&pdev->dev);
-- 
2.17.1