On Armada 7K/8K we need to explicitly enable the register clock. This
clock is optional because not all the SoCs using this IP need it but at
least for Armada 7K/8K it is actually mandatory.

The change was done at xhci-plat level and not at a xhci-mvebu.c because,
it is expected that other SoC would have this kind of constraint.

The binding documentation is updating accordingly.

Signed-off-by: Gregory CLEMENT <gregory.clem...@bootlin.com>
---
 Documentation/devicetree/bindings/usb/usb-xhci.txt |  5 ++++-
 drivers/usb/host/xhci-plat.c                       | 25 ++++++++++++++++++----
 drivers/usb/host/xhci.h                            |  3 ++-
 3 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt 
b/Documentation/devicetree/bindings/usb/usb-xhci.txt
index c4c00dff4b56..bd1dd316fb23 100644
--- a/Documentation/devicetree/bindings/usb/usb-xhci.txt
+++ b/Documentation/devicetree/bindings/usb/usb-xhci.txt
@@ -28,7 +28,10 @@ Required properties:
   - interrupts: one XHCI interrupt should be described here.
 
 Optional properties:
-  - clocks: reference to a clock
+  - clocks: reference to the clocks
+  - clock-names: mandatory if there is a second clock, in this case
+    the name must be "core" for the first clock and "reg" for the
+    second one
   - usb2-lpm-disable: indicate if we don't want to enable USB2 HW LPM
   - usb3-lpm-capable: determines if platform is USB3 LPM capable
   - quirk-broken-port-ped: set if the controller has broken port disable 
mechanism
diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index f0231fea524e..596e7a71b666 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -157,6 +157,7 @@ static int xhci_plat_probe(struct platform_device *pdev)
        struct resource         *res;
        struct usb_hcd          *hcd;
        struct clk              *clk;
+       struct clk              *reg_clk;
        int                     ret;
        int                     irq;
 
@@ -226,17 +227,27 @@ static int xhci_plat_probe(struct platform_device *pdev)
        hcd->rsrc_len = resource_size(res);
 
        /*
-        * Not all platforms have a clk so it is not an error if the
-        * clock does not exists.
+        * Not all platforms have clks so it is not an error if the
+        * clock do not exist.
         */
+       reg_clk = devm_clk_get(&pdev->dev, "reg");
+       if (!IS_ERR(reg_clk)) {
+               ret = clk_prepare_enable(reg_clk);
+               if (ret)
+                       goto put_hcd;
+       } else if (PTR_ERR(reg_clk) == -EPROBE_DEFER) {
+               ret = -EPROBE_DEFER;
+               goto put_hcd;
+       }
+
        clk = devm_clk_get(&pdev->dev, NULL);
        if (!IS_ERR(clk)) {
                ret = clk_prepare_enable(clk);
                if (ret)
-                       goto put_hcd;
+                       goto disable_reg_clk;
        } else if (PTR_ERR(clk) == -EPROBE_DEFER) {
                ret = -EPROBE_DEFER;
-               goto put_hcd;
+               goto disable_reg_clk;
        }
 
        xhci = hcd_to_xhci(hcd);
@@ -252,6 +263,7 @@ static int xhci_plat_probe(struct platform_device *pdev)
        device_wakeup_enable(hcd->self.controller);
 
        xhci->clk = clk;
+       xhci->reg_clk = reg_clk;
        xhci->main_hcd = hcd;
        xhci->shared_hcd = __usb_create_hcd(driver, sysdev, &pdev->dev,
                        dev_name(&pdev->dev), hcd);
@@ -322,6 +334,9 @@ static int xhci_plat_probe(struct platform_device *pdev)
 disable_clk:
        clk_disable_unprepare(clk);
 
+disable_reg_clk:
+       clk_disable_unprepare(reg_clk);
+
 put_hcd:
        usb_put_hcd(hcd);
 
@@ -337,6 +352,7 @@ static int xhci_plat_remove(struct platform_device *dev)
        struct usb_hcd  *hcd = platform_get_drvdata(dev);
        struct xhci_hcd *xhci = hcd_to_xhci(hcd);
        struct clk *clk = xhci->clk;
+       struct clk *reg_clk = xhci->reg_clk;
 
        xhci->xhc_state |= XHCI_STATE_REMOVING;
 
@@ -347,6 +363,7 @@ static int xhci_plat_remove(struct platform_device *dev)
        usb_put_hcd(xhci->shared_hcd);
 
        clk_disable_unprepare(clk);
+       clk_disable_unprepare(reg_clk);
        usb_put_hcd(hcd);
 
        pm_runtime_set_suspended(&dev->dev);
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 05c909b04f14..6dfc4867dbcf 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1729,8 +1729,9 @@ struct xhci_hcd {
        int             page_shift;
        /* msi-x vectors */
        int             msix_count;
-       /* optional clock */
+       /* optional clocks */
        struct clk              *clk;
+       struct clk              *reg_clk;
        /* data structures */
        struct xhci_device_context_array *dcbaa;
        struct xhci_ring        *cmd_ring;
-- 
2.16.3

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