linux-kernel - Re: [PATCH 1/2 v3] tcpm: During PR_SWAP, source caps should be sent only after tSwapSourceStart

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Date:   Mon, 17 Aug 2020 11:07:23 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Badhri Jagan Sridharan <badhri@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2 v3] tcpm: During PR_SWAP, source caps should be sent
 only after tSwapSourceStart

On Thu, Aug 13, 2020 at 12:40:04PM -0700, Badhri Jagan Sridharan wrote:
> Hi Heikki,
> 
> Sure. Same as the other patch I will try to address your question here
> and will update the commit description once you are satisfied with the
> description.
> 
> Subject:
> During PR_SWAP, source caps should be sent only after tSwapSourceStart
> 
> Commit description:
> The patch addresses the compliance test failures while running
> TD.PD.CP.E3, TD.PD.CP.E4, TD.PD.CP.E5 of the "Deterministic PD
> Compliance MOI" test plan published in https://www.usb.org/usbc.
> For a product to be Type-C compliant, it's expected that these tests
> are run on usb.org certified Type-C compliance tester as mentioned in
> https://www.usb.org/usbc.
> 
> The purpose of the tests TD.PD.CP.E3, TD.PD.CP.E4, TD.PD.CP.E5 is to
> verify the PR_SWAP response of the device. While doing so, the test
> asserts that Source Capabilities message is NOT received from the test
> device within tSwapSourceStart min (20 ms) from the time the last bit
> of GoodCRC corresponding to the RS_RDY message sent by the UUT was
> sent. If it does then the test fails.
> 
> This is in line with the requirements from the USB Power Delivery
> Specification Revision 3.0, Version 1.2:
> "6.6.8.1 SwapSourceStartTimer
> The SwapSourceStartTimer Shall be used by the new Source, after a
> Power Role Swap or Fast Role Swap, to ensure that it does not send
> Source_Capabilities Message before the new Sink is ready to receive
> the
> Source_Capabilities Message. The new Source Shall Not send the
> Source_Capabilities Message earlier than tSwapSourceStart after the
> last bit of the EOP of GoodCRC Message sent in response to the PS_RDY
> Message sent by the new Source indicating that its power supply is
> ready."
> 
> The patch makes sure that TCPM does not send the Source_Capabilities
> Message within tSwapSourceStart(20ms) by transitioning into
> SRC_STARTUP only after  tSwapSourceStart(20ms).

That looks good to me. Thanks.

Br,

-- 
heikki