linux-kernel - Re: [PATCH v2, 2/2] usb: typec: tcpm: fix the sender response time issue

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Message-ID: <exu4kkmysquqfygz4gk26kfzediyqmq3wsxvu5ro454mi4fgyp@gr44ymyyxmng>
Date: Sun, 22 Dec 2024 15:13:55 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: joswang <joswang1221@...il.com>
Cc: heikki.krogerus@...ux.intel.com, robh@...nel.org, krzk+dt@...nel.org, 
	conor+dt@...nel.org, gregkh@...uxfoundation.org, linux-usb@...r.kernel.org, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, rdbabiera@...gle.com, 
	Jos Wang <joswang@...ovo.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2, 2/2] usb: typec: tcpm: fix the sender response time
 issue

On Sun, Dec 22, 2024 at 06:52:39PM +0800, joswang wrote:
> From: Jos Wang <joswang@...ovo.com>
> 
> According to the USB PD3 CTS specification
> (https://usb.org/document-library/
> usb-power-delivery-compliance-test-specification-0/
> USB_PD3_CTS_Q4_2024_OR.zip), the requirements for
> tSenderResponse are different in PD2 and PD3 modes, see
> Table 19 Timing Table & Calculations. For PD2 mode, the
> tSenderResponse min 24ms and max 30ms; for PD3 mode, the
> tSenderResponse min 27ms and max 33ms.
> 
> For the "TEST.PD.PROT.SRC.2 Get_Source_Cap No Request" test
> item, after receiving the Source_Capabilities Message sent by
> the UUT, the tester deliberately does not send a Request Message
> in order to force the SenderResponse timer on the Source UUT to
> timeout. The Tester checks that a Hard Reset is detected between
> tSenderResponse min and max，the delay is between the last bit of
> the GoodCRC Message EOP has been sent and the first bit of Hard
> Reset SOP has been received. The current code does not distinguish
> between PD2 and PD3 modes, and tSenderResponse defaults to 60ms.
> This will cause this test item and the following tests to fail:
> TEST.PD.PROT.SRC3.2 SenderResponseTimer Timeout
> TEST.PD.PROT.SNK.6 SenderResponseTimer Timeout
> 
> Considering factors such as SOC performance, i2c rate, and the speed
> of PD chip sending data, "pd2-sender-response-time-ms" and
> "pd3-sender-response-time-ms" DT time properties are added to allow
> users to define platform timing. For values that have not been
> explicitly defined in DT using this property, a default value of 27ms
> for PD2 tSenderResponse and 30ms for PD3 tSenderResponse is set.

You have several different changes squashed into the same commit:
- Change the timeout from 60 ms to 27-30 ms (I'd recommend using 27 ms
  as it fits both 24-30 ms and 27-33 ms ranges,
- Make timeout depend on the PD version,
- Make timeouts configurable via DT.

Only the first item is a fix per se and only that change should be
considered for backporting. Please unsquash your changes into logical
commits.  Theoretically the second change can be thought about as a part
of the third change (making timeouts configurable) or of the fist change
(fix the timeout to follow the standard), but I'd suggest having three
separate commits.

> 
> Fixes: 2eadc33f40d4 ("typec: tcpm: Add core support for sink side PPS")
> Cc: stable@...r.kernel.org
> Signed-off-by: Jos Wang <joswang@...ovo.com>
> ---
> v1 -> v2:
> - modify the commit message
> - patch 1/2 and patch 2/2 are placed in the same thread

-- 
With best wishes
Dmitry