linux-kernel - Re: [PATCH 1/1] usb: pd: fix the SenderResponseTimer conform to specification

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Message-ID: <CAMtoTm1xeviEXJGCAECF65RidexGTG9pjKhU8OyW17rOq7evfA@mail.gmail.com>
Date: Wed, 8 Jan 2025 22:49:44 +0800
From: Jos Wang <joswang1221@...il.com>
To: dmitry.baryshkov@...aro.org
Cc: gregkh@...uxfoundation.org, linux-usb@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Jos Wang <joswang@...ovo.com>, stable@...r.kernel.org, 
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: Re: [PATCH 1/1] usb: pd: fix the SenderResponseTimer conform to specification

On Sun, Jan 5, 2025 at 8:53 PM joswang <joswang1221@...il.com> 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
>
> Set the SenderResponseTimer timeout to 27ms to meet the PD2
> and PD3 mode requirements.
>
> Fixes: f0690a25a140 ("staging: typec: USB Type-C Port Manager (tcpm)")
> Cc: stable@...r.kernel.org
> Signed-off-by: Jos Wang <joswang@...ovo.com>
> ---
>  include/linux/usb/pd.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/usb/pd.h b/include/linux/usb/pd.h
> index 3068c3084eb6..99ca49bbf376 100644
> --- a/include/linux/usb/pd.h
> +++ b/include/linux/usb/pd.h
> @@ -475,7 +475,7 @@ static inline unsigned int rdo_max_power(u32 rdo)
>  #define PD_T_NO_RESPONSE       5000    /* 4.5 - 5.5 seconds */
>  #define PD_T_DB_DETECT         10000   /* 10 - 15 seconds */
>  #define PD_T_SEND_SOURCE_CAP   150     /* 100 - 200 ms */
> -#define PD_T_SENDER_RESPONSE   60      /* 24 - 30 ms, relaxed */
> +#define PD_T_SENDER_RESPONSE   27      /* 24 - 30 ms */
>  #define PD_T_RECEIVER_RESPONSE 15      /* 15ms max */
>  #define PD_T_SOURCE_ACTIVITY   45
>  #define PD_T_SINK_ACTIVITY     135
> --
> 2.17.1
>

Hi Dmitry

Discuss here "https://patchwork.kernel.org/project/linux-usb/patch/20241222105239.2618-2-joswang1221@gmail.com/",
you suggest setting PD_T_SENDER_RESPONSE to 27ms.
1、In actual testing, setting the timeout to 27ms can solve the CTS
problem in PD2 mode. For PD3 mode, since 27ms is at the boundary, it
cannot solve the CTS problem well.
For example, in the test item “TEST.PD.PROT.SRC.3 SenderResponseTimer
Deadline (As a Sink, the Tester checks that the UUT accepts a Request
Message sent at the deadline limit of tSenderResponse min in reply to
a Source_Capabilities Message.)”, after the Tester (sink) receives the
Source_cap message, it will send a Request message 25.26 ms later. The
tcpm framework layer on the source side should take more than 2
seconds to receive and process the Request message，which means that a
Hard Reset may be sent before the Request message is fully processed.
2、The current modification is as follows:
#define PD_T_SENDER_RESPONSE 27 /* I am confused by the comments here,
such as 24ms - 30ms or 24ms - 33 ms or others */
There is no suitable comment here. In the next patch "Make timeout
depend on the PD version", this line of code may need to be modified
again.
In summary, I might consider including the following changes in one commit:
(1) include/linux/usb/pd.h
+#define PD_T_PD2_SENDER_RESPONSE 27 /* PD20 spec 24 - 30 ms */
+#define PD_T_PD3_SENDER_RESPONSE 30 /* PD30 spec 27 - 33 ms */
(2) drivers/usb/typec/tcpm/tcpm.c
Make timeout depend on the PD version
In fact, it is to patch "[v2,2/2] usb: typec: tcpm: fix the sender
response time issue", remove "Make timeouts configurable via DT"

Do you have a better idea?

Thanks

Jos Wang