usb: dwc3: support clocks and resets for DWC3 core

Historically, the clocks and resets are handled on the glue layer
side instead of the DWC3 core.  For simple cases, dwc3-of-simple.c
takes care of arbitrary number of clocks and resets.  The DT node
structure typically looks like as follows:

  dwc3-glue {
          compatible = "foo,dwc3";
          clocks = ...;
          resets = ...;
          ...

          dwc3 {
                  compatible = "snps,dwc3";
                  ...
          };
  }

By supporting the clocks and the reset in the dwc3/core.c, it will
be turned into a single node:

  dwc3 {
          compatible = "foo,dwc3", "snps,dwc3";
          clocks = ...;
          resets = ...;
          ...
  }

This commit adds the binding of clocks and resets specific to this IP.
The number of clocks should generally be the same across SoCs, it is
just some SoCs either tie clocks together or do not provide software
control of some of the clocks.

I took the clock names from the Synopsys datasheet: "ref" (ref_clk),
"bus_early" (bus_clk_early), and "suspend" (suspend_clk).

I found only one reset line in the datasheet, hence the reset-names
property is omitted.

Those clocks are required for new platforms.  Enforcing the new
binding breaks existing platforms since they specify clocks (and
resets) in their glue layer node, but nothing in the core node.
I listed such exceptional cases in the DT binding.  The driver
code has been relaxed to accept no clock.  This change is based
on the discussion [1].

I inserted reset_control_deassert() and clk_bulk_enable() before the
first register access, i.e. dwc3_cache_hwparams().

[1] https://patchwork.kernel.org/patch/10284265/

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 4f3b43809917..1765e014aa08 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -891,6 +891,9 @@ struct dwc3_scratchpad_array {
  * @eps: endpoint array
  * @gadget: device side representation of the peripheral controller
  * @gadget_driver: pointer to the gadget driver
+ * @clks: array of clocks
+ * @num_clks: number of clocks
+ * @reset: reset control
  * @regs: base address for our registers
  * @regs_size: address space size
  * @fladj: frame length adjustment
@@ -1013,6 +1016,11 @@ struct dwc3 {
 	struct usb_gadget	gadget;
 	struct usb_gadget_driver *gadget_driver;
 
+	struct clk_bulk_data	*clks;
+	int			num_clks;
+
+	struct reset_control	*reset;
+
 	struct usb_phy		*usb2_phy;
 	struct usb_phy		*usb3_phy;