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SubjectRe: [PATCH v2 2/2] usb: dwc3: support clocks and resets for DWC3 core
On Thu, Apr 19, 2018 at 08:03:38PM +0900, Masahiro Yamada wrote:
> 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.
>
> Supporting those clocks and resets is the requirement 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 is loosened up to accept no clock/reset. 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>
> ---
>
> Changes in v2:
> - Make clocks specific to this IP based on Synopsys datasheet
> - Use clk_bulk API
> - Add description to struct header
>
> Documentation/devicetree/bindings/usb/dwc3.txt | 21 ++++++
> drivers/usb/dwc3/core.c | 89 +++++++++++++++++++++++++-
> drivers/usb/dwc3/core.h | 8 +++
> 3 files changed, 116 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
> index 0dbd308..feb1cc33 100644
> --- a/Documentation/devicetree/bindings/usb/dwc3.txt
> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
> @@ -7,6 +7,27 @@ Required properties:
> - compatible: must be "snps,dwc3"
> - reg : Address and length of the register set for the device
> - interrupts: Interrupts used by the dwc3 controller.
> + - clock-names: should contain "ref", "bus_early", "suspend"
> + - clocks: list of phandle and clock specifier pairs corresponding to
> + entries in the clock-names property.
> + - resets: a single pair of phandle and reset specifier

This should be optional as some SoCs don't have separate, s/w controlled
resets of modules.

Otherise, for the DT binding:

Reviewed-by: Rob Herring <robh@kernel.org>

Rob

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