linux-kernel - Re: [PATCH v2] usb: typec: tcpm: fix multiple times discover svids error

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Date:   Thu, 20 Apr 2023 06:49:03 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Frank Wang <frank.wang@...k-chips.com>, heiko@...ech.de,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, huangtao@...k-chips.com,
        william.wu@...k-chips.com, jianwei.zheng@...k-chips.com,
        yubing.zhang@...k-chips.com, wmc@...k-chips.com
Subject: Re: [PATCH v2] usb: typec: tcpm: fix multiple times discover svids
 error

On 4/20/23 01:08, Greg KH wrote:
> On Fri, Mar 17, 2023 at 01:27:13PM +0200, Heikki Krogerus wrote:
>> On Thu, Mar 16, 2023 at 04:11:49PM +0800, Frank Wang wrote:
>>> PD3.0 Spec 6.4.4.3.2 say that only Responder supports 12 or more SVIDs,
>>> the Discover SVIDs Command Shall be executed multiple times until a
>>> Discover SVIDs VDO is returned ending either with a SVID value of
>>> 0x0000 in the last part of the last VDO or with a VDO containing two
>>> SVIDs with values of 0x0000.
>>>
>>> In the current implementation, if the last VDO does not find that the
>>> Discover SVIDs Command would be executed multiple times even if the
>>> Responder SVIDs are less than 12, and we found some odd dockers just
>>> meet this case. So fix it.
>>>
>>> Signed-off-by: Frank Wang <frank.wang@...k-chips.com>
>>> ---
>>>   drivers/usb/typec/tcpm/tcpm.c | 16 +++++++++++++++-
>>>   1 file changed, 15 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
>>> index 66de02a56f512..a3ae2c79f3540 100644
>>> --- a/drivers/usb/typec/tcpm/tcpm.c
>>> +++ b/drivers/usb/typec/tcpm/tcpm.c
>>> @@ -1515,7 +1515,21 @@ static bool svdm_consume_svids(struct tcpm_port *port, const u32 *p, int cnt)
>>>   		pmdata->svids[pmdata->nsvids++] = svid;
>>>   		tcpm_log(port, "SVID %d: 0x%x", pmdata->nsvids, svid);
>>>   	}
>>> -	return true;
>>> +
>>> +	/*
>>> +	 * PD3.0 Spec 6.4.4.3.2: The SVIDs are returned 2 per VDO (see Table
>>> +	 * 6-43), and can be returned maximum 6 VDOs per response (see Figure
>>> +	 * 6-19). If the Respondersupports 12 or more SVID then the Discover
>>> +	 * SVIDs Command Shall be executed multiple times until a Discover
>>> +	 * SVIDs VDO is returned ending either with a SVID value of 0x0000 in
>>> +	 * the last part of the last VDO or with a VDO containing two SVIDs
>>> +	 * with values of 0x0000.
>>> +	 *
>>> +	 * However, some odd dockers support SVIDs less than 12 but without
>>> +	 * 0x0000 in the last VDO, so we need to break the Discover SVIDs
>>> +	 * request and return false here.
>>> +	 */
>>> +	return cnt == 7;
>>>   abort:
>>>   	tcpm_log(port, "SVID_DISCOVERY_MAX(%d) too low!", SVID_DISCOVERY_MAX);
>>>   	return false;
>>
>> This is OK by men, but let's wait for Guenter.
> 
> What ever happened to this patch?
> 

It got lost in space.

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

Guenter