From: Rob Herring <robh@kernel.org>
To: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Cc: Felipe Balbi <balbi@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-usb@vger.kernel.org, devicetree@vger.kernel.org,
John Youn <John.Youn@synopsys.com>
Subject: Re: [PATCH v2 06/12] usb: devicetree: Introduce num-lanes and lsm
Date: Thu, 23 Jul 2020 14:29:36 -0600 [thread overview]
Message-ID: <20200723202936.GA801155@bogus> (raw)
In-Reply-To: <d605a437f0a4bc837a05269caaa3875c2e0b29d8.1595468673.git.thinhn@synopsys.com>
On Wed, Jul 22, 2020 at 07:12:39PM -0700, Thinh Nguyen wrote:
> According to USB 3.2 spec, a super-speed-plus device can operate at
> gen2x2, gen2x1, or gen1x2. Introduce "num-lanes" and
> "lane-speed-mantissa-gbps" properties for devices operating in
> super-speed-plus. If the USB controller device supports multiple lanes
> at different transfer rate, the user can specify the HW capability via
> these properties.
>
> Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
> ---
> Changes in v2:
> - Make "num-lanes" and "lane-speed-mantissa-gbps" common USB properties
>
> Documentation/devicetree/bindings/usb/generic.txt | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/usb/generic.txt b/Documentation/devicetree/bindings/usb/generic.txt
> index ba472e7aefc9..a8253da684af 100644
> --- a/Documentation/devicetree/bindings/usb/generic.txt
> +++ b/Documentation/devicetree/bindings/usb/generic.txt
> @@ -7,6 +7,17 @@ Optional properties:
> "low-speed". In case this isn't passed via DT, USB
> controllers should default to their maximum HW
> capability.
> + - num-lanes: tells USB controllers that we want to work up to a certain number
> + of lanes. Valid arguments are 1 or 2. Apply if the
> + maximum-speed is super-speed-plus. In case this isn't
> + passed via DT, the USB controllers should default to
> + their maximum HW capability.
> + - lane-speed-mantissa-gbps: tells USB controllers that we want the symmetric
> + lanes to operate up to a certain rate in Gbps. Valid
> + inputs are 5 or 10 (i.e. Gen 1/Gen 2 transfer rate).
> + Apply if the maximum-speed is super-speed-plus. In case
> + this isn't passed via DT, the USB controllers should
> + default to their maximum HW capability.
This still leaves 'maximum-speed = "super-speed-plus"' ambiguous. Fix
that please.
To put it another way, we already have one way to define USB speeds.
Don't define a new and different way that only covers a fraction of the
possibilities.
Rob
next prev parent reply other threads:[~2020-07-23 20:29 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 2:12 [PATCH v2 00/12] usb: Handle different sublink speeds Thinh Nguyen
2020-07-23 2:12 ` [PATCH v2 06/12] usb: devicetree: Introduce num-lanes and lsm Thinh Nguyen
2020-07-23 20:29 ` Rob Herring [this message]
2020-07-24 2:39 ` Thinh Nguyen
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