linux-kernel - Re: [PATCH v2] usb: dwc3: core: enable CCI support for AMD-xilinx DWC3 controller

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Message-ID: <20240320004810.6omwumwbcxk5as4k@synopsys.com>
Date: Wed, 20 Mar 2024 00:48:14 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: "Pandey, Radhey Shyam" <radhey.shyam.pandey@....com>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski@...aro.org>,
        Rob Herring <robh+dt@...nel.org>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "Simek, Michal" <michal.simek@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "git (AMD-Xilinx)" <git@....com>
Subject: Re: [PATCH v2] usb: dwc3: core: enable CCI support for AMD-xilinx
 DWC3 controller

+devicetree maintainers

On Mon, Mar 18, 2024, Pandey, Radhey Shyam wrote:
> > 
> > Instead, perhaps we can do it as following:
> >  * Keep the setting of the controller registers in the core
> >  * Create a software_node to pass a software property to the core
> Thanks. By software property you mean flags or caps that can be passed
> glue drivers to dwc3 core driver ?
> 
> dwc3_set_quirks(struct dwc3 *dwc, u64 flags);
> 
> Defines quirks in core.h
> 
> DWC3_FLAGS_COMMON
> DWC3_XLNX_CCI
> DWC3_XLNX_IPD
> DWC3_REALTEK_RES_FIX
> 
> Then based on these quirks/flags program it in core.c.
> Is this approach fine and aligned with your thoughts?
> 

Not as a flag. Create 4 properties for GSBUSCFG0.DATRDREQINFO,
DESRDREQINFO, DATWRREQINFO, and DESWRREQINFO in your glue driver. Pass
them through your software node as PROPERTY_ENTRY_U16. The core will
override the default coreConsultant value of GSBUSCFG0 based on these
properties in dwc3_get_properties().

Check drivers/usb/dwc3/host.c for reference.

> 
> > 
> > These software properties will not be documented in the devicetree
> > binding. Just document them in the driver core header. They are simply
> > driver properties that get passed through software node.
> > 
> > You can add the software node using device_add_software_node(). This can
> > be done before calling of_platform_populate() in dwc3-xilinx (can be
> > done in pltfm_init())
> > 
> > Let me know if this works for you.
> > 

Hi Rob/Krzysztof,

Just want to check in with you for your opinion. To summarize my
suggestion to Pandey, here are the key notes:
* Platform specific settings are set in glue drivers (match through
  compatible string)
* These settings are set by controller registers that should only
  be accessible in the dwc3 core
* So, the suggestion is to pass these settings as properties using
  software_node created from the glue driver to the dwc3 core
* These properties will not be documented in the devicetree binding, but
  only in the driver

We're already doing that to some properties such as
"linux,sysdev_is_parent"

If this suggestion makes sense, would the prefix "linux," for linux
specific binding or "snps," is a better fit?

Thanks,
Thinh