linux-kernel - Re: [PATCH 1/2] dt-bindings: usb: dwc3: Add binding for USB Gen2 de-emphasis

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAOSNQF1A_gsXeRuuR4qeZQi9FicrsPxYfjvLpmgxkaGq0-mZmA@mail.gmail.com>
Date: Tue, 8 Oct 2024 18:10:10 +0530
From: Joy Chakraborty <joychakr@...gle.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Thinh Nguyen <Thinh.Nguyen@...opsys.com>, Felipe Balbi <balbi@...nel.org>, linux-usb@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: usb: dwc3: Add binding for USB Gen2 de-emphasis

On Tue, Oct 8, 2024 at 5:40 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On 08/10/2024 13:59, Joy Chakraborty wrote:
> >>>
> >>>>
> >>>>> +    description: When set core will set Tx de-emphasis for USB Gen2
> >>>>
> >>>> And why it cannot be implied by compatible?
> >>>
> >>> As per my understanding these are tuning coefficients for de-emphasis
> >>> particular to a platform and not the dwc3 controller, hence should not
> >>> be a controller compatible.
> >>
> >> Platforms must have specific compatible, so this should be implied by
> >> compatible.
> >
> > Maybe I am using the word "platform" incorrectly here, what I
> > understand is that the same controller(in a chip) when used on 2
> > different physical form factors might need different deemphasis
>
> You mean boards? This is board-level property?

Yes, the USB controller can be paired with different phys in a SoC and
used on different board layouts where we should be able to drive
different de-emphasis coefficients to the phy as per the link
equalization requirements is my understanding.

>
> > coefficient values to be passed to its Phy. Someone could correct me
> > from the USB link stand point if I am mistaken here.
> >
>
> Then please point me to the upstream DTS boards using these properties.
> Lore link is enough, if board or DTS change is being upstreamed.
>

The DTS change is not being upstreamed currently.
But this change would help bring up a new or development board where
USB compliance is being run and this parameter needs tuning,  hence
being able to upstream this would help.

> Best regards,
> Krzysztof
>