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

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Message-ID: <CAMtoTm2jEWQHKp2hOO7ngG1KosqH4sxgG=fg7qoHqe7Ei5DuHQ@mail.gmail.com>
Date: Mon, 6 Jan 2025 21:25:17 +0800
From: Jos Wang <joswang1221@...il.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: heikki.krogerus@...ux.intel.com, dmitry.baryshkov@...aro.org, 
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Jos Wang <joswang@...ovo.com>, stable@...r.kernel.org
Subject: Re: [PATCH 1/1] usb: pd: fix the SenderResponseTimer conform to specification

On Sun, Jan 5, 2025 at 9:00 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Sun, Jan 05, 2025 at 08:52:51PM +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
>
> Please put urls on one line so that they can be linked to correctly.
>

OK，Thanks

> > 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 */
>
> Why 27 and not 30?  The comment seems odd here, right?
>

1、As mentioned in the commit message, "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. Since it takes
time for the tcpm framework layer to initiate a Hard Reset (writing
the PD PHY register through I2C operation), setting tSenderResponse to
30ms (PD2.0 spec max) will cause this test item to fail in PD2.0 mode.

2、The comments here are indeed unreasonable, how about modifying it like this?
+#define PD_T_SENDER_RESPONSE 27 /* PD2.0 spec 24ms -30ms, PD3.1 spec
27ms - 33ms, setting 27ms meets the requirements of PD2.0 and PD3.1.
*/

3、This patch was originally discussed here
(https://patchwork.kernel.org/project/linux-usb/patch/20241222105239.2618-2-joswang1221@gmail.com/)
Dmitry Baryshkov suggested splitting the "[v2,2/2] usb: typec: tcpm:
fix the sender response time issue" patch and submitting it
separately.
(1) Set SenderResponse timer timeout to 27ms
(2) Make timeout depend on the PD version
(3) Make timeouts configurable via DT
Actually, I would prefer to merge (1) and (2) and submit them. Do you
have any better suggestions?

> thanks,
>
> greg k-h