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From: Matthias Kaehlcke <>
To: Krzysztof Kozlowski <>
Cc: Greg Kroah-Hartman <>,
	Rob Herring <>,
	Frank Rowand <>,, Peter Chen <>,
	Stephen Boyd <>,
	Alan Stern <>,
	Ravi Chandra Sadineni <>,
	Bastien Nocera <>,,
	Douglas Anderson <>,, Al Cooper <>,
	"Alexander A. Klimov" <>,
	Andy Gross <>,
	Bjorn Andersson <>,
	Masahiro Yamada <>,
	Mathias Nyman <>,
Subject: Re: [PATCH v5 0/4] USB: misc: Add onboard_usb_hub driver
Date: Wed, 10 Feb 2021 14:37:30 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <20210210210451.3coi62cynptzb6wf@kozik-lap>

Hi Krzysztof,

On Wed, Feb 10, 2021 at 10:04:51PM +0100, Krzysztof Kozlowski wrote:
> On Wed, Feb 10, 2021 at 09:10:35AM -0800, Matthias Kaehlcke wrote:
> > This series adds the onboard_usb_hub_driver, the corresponding
> > device tree bindings and creation of onboard_usb_hub platform in
> > the xhci-plat driver during probe().
> > 
> > The main issue the driver addresses is that a USB hub needs to be
> > powered before it can be discovered. For discrete onboard hubs (an
> > example for such a hub is the Realtek RTS5411) this is often solved
> > by supplying the hub with an 'always-on' regulator, which is kind
> > of a hack.
> It seems you are re-developing the power sequence drivers which perform
> exactly this. Peter Chen some time ago was bringing power sequence to
> USB devices, but I lost track where this ended up.
> Some of his (and my) very old work (2017...) can be found here:

pwrseq was brought up in the discussion about this driver, but wasn't
deemed suitable for this use case which might require more complex

> Instead of adding custom driver hiding some USB hub implementation,
> power sequence seems a generic solution. What if you need to power cycle
> other embedded USB device? Not a hub?

The driver could be extended to also cover other types of devices if desired.
Maybe it should be called usb-pwrseq then, even though it's not directly
related with the original pwrseq series.

  reply	other threads:[~2021-02-10 22:38 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-10 17:10 [PATCH v5 0/4] USB: misc: Add onboard_usb_hub driver Matthias Kaehlcke
2021-02-10 17:10 ` [PATCH v5 4/4] arm64: dts: qcom: sc7180-trogdor: Add nodes for onboard USB hub Matthias Kaehlcke
2021-02-10 21:04 ` [PATCH v5 0/4] USB: misc: Add onboard_usb_hub driver Krzysztof Kozlowski
2021-02-10 22:37   ` Matthias Kaehlcke [this message]
2021-02-24 13:25 ` Michal Simek

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