linux-kernel - Re: [v5 PATCH 1/5] extcon: Add Type-C and DP support

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Message-id: <5786E1B6.2000805@samsung.com>
Date:	Thu, 14 Jul 2016 09:49:58 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Chris Zhong <zyw@...k-chips.com>, dianders@...omium.org,
	tfiga@...omium.org, heiko@...ech.de, yzq@...k-chips.com,
	groeck@...omium.org, myungjoo.ham@...sung.com, wulf@...k-chips.com,
	marcheu@...omium.org
Cc:	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [v5 PATCH 1/5] extcon: Add Type-C and DP support

Hi Chris,

On 2016년 07월 13일 11:54, Chris Zhong wrote:
> Hi Chanwoo Choi
> 
> On 07/13/2016 10:05 AM, Chanwoo Choi wrote:
>> Hi Chris,
>>
>> On 2016년 07월 13일 10:39, Chris Zhong wrote:
>>> Hi Chanwoo Choi
>>>
>>>
>>> On 07/13/2016 09:11 AM, Chanwoo Choi wrote:
>>>> Hi Chris,
>>>>
>>>> I'm now developing the extcon property on extcon-test branch.
>>>> But, it has not been completed.
>>>>
>>>> On next version, I'll remove the notification about extcon property
>>>> and only support the following two functions.
>>>> - extcon_set_cable_property()
>>>> - extcon_get_cable_property()
>>>>
>>>> Because the number of properties would be risen and the all properties
>>>> depend on the specific external connector(e.g., EXTCON_PROP_USB_VBUS
>>>> depend on the EXTCON_TYPE_USB type). When the specific external connector
>>>> is detached, extcon framework should make the property state as default state.
>>> Yes, I think getting the notification from cable state is enough, actually I am using it like you said.
>> OK.
>>
>>>> It may send the too many notification for extcon property.
>>>> For example, Assume that EXTCON_TYPE_USB has the over 20 properties,
>>>> when EXTCON_USB or EXTCON_USB_HOST is detached, extcon should send
>>>> the notification for the over 20 properties and one more notificaiton
>>>> for state of external connector.
>>>>
>>>> So, I'll send the RFC patchset without the notification of proerty.
>>>>
>>>> Lastly,
>>>> I have a comment on below.
>>>>
>>>> Thanks,
>>>> Chanwoo Choi
>>>>
>>>> On 2016년 07월 13일 00:09, Chris Zhong wrote:
>>>>> Add EXTCON_DISP_DP for the Display external connector. For Type-C
>>>>> connector the DisplayPort can work as an Alternate Mode(VESA DisplayPort
>>>>> Alt Mode on USB Type-C Standard). The Type-C support both normal and
>>>>> flipped orientation, so add a property to extcon.
>>>>>
>>>>> Signe-off-by: Chris Zhong <zyw@...k-chips.com>
>>>>>
>>>>> Signed-off-by: Chris Zhong <zyw@...k-chips.com>
>>>>> ---
>>>>>
>>>>> Changes in v5:
>>>>> - support get property
>>>>>
>>>>> Changes in v4: None
>>>>> Changes in v3: None
>>>>> Changes in v2: None
>>>>> Changes in v1: None
>>>>>
>>>>>    drivers/extcon/extcon.c | 28 ++++++++++++++++++++++++++++
>>>>>    include/linux/extcon.h  | 13 +++++++++++++
>>>>>    2 files changed, 41 insertions(+)
>>>>>
>>>>> diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
>>>>> index a1117db..2591b28 100644
>>>>> --- a/drivers/extcon/extcon.c
>>>>> +++ b/drivers/extcon/extcon.c
>>>>> @@ -157,6 +157,11 @@ struct __extcon_info {
>>>>>            .id = EXTCON_DISP_VGA,
>>>>>            .name = "VGA",
>>>>>        },
>>>>> +    [EXTCON_DISP_DP] = {
>>>>> +        .type = EXTCON_TYPE_DISP,
>>>>> +        .id = EXTCON_DISP_DP,
>>>>> +        .name = "DP",
>>>>> +    },
>>>>>          /* Miscellaneous external connector */
>>>>>        [EXTCON_DOCK] = {
>>>>> @@ -270,6 +275,7 @@ static bool is_extcon_property_supported(unsigned int id,
>>>>>            switch (prop) {
>>>>>            case EXTCON_PROP_USB_ID:
>>>>>            case EXTCON_PROP_USB_VBUS:
>>>>> +        case EXTCON_PROP_TYPEC_POLARITY:
>>>>>                return true;
>>>>>            default:
>>>>>                break;
>>>>> @@ -286,6 +292,8 @@ static bool is_extcon_property_supported(unsigned int id,
>>>>>            }
>>>>>        case EXTCON_TYPE_DISP:
>>>>>            switch (prop) {
>>>>> +        case EXTCON_PROP_TYPEC_POLARITY:
>>>> Should EXTCON_PROP_TYPEC_POLARITY property add to both EXTCON_TYPE_USB and EXTCON_TYP_DISP?
>>>> EXTCON_PROP_TYPEC_POLARITY is the property of USB C-type?
>>> it is for USB Type-C, But at Display Port alt mode, both EXTCON_USB and EXTCON_USB_HOST may be detached. Does it support set the property to a detached cable, if so, I think move this case to EXTCON_USB is fine.
>> One external connector can set the state of one more external connector
>> if the one connector support the various functions.
>> For example, EXTCON_USB and EXTCON_CHG_USB_SDP
>> The existing extcon driver[1](e.g., max14577/max77693 etc.) set the state of both EXTCON_USB and EXTCON_CHG_USB_SDP connector at the same time
>> when usb cable is attached. Because in this case, the usb connector uses as both power supply(EXTCON_CHG_USB_SDP) and data transfer(EXTCON_USB).
>> [1] https://git.kernel.org/cgit/linux/kernel/git/chanwoo/extcon.git/commit/?h=extcon-next&id=8b45b6a0741678902810d7be95e635c210fbb198
>>
>> So, DP Alt mode uses the USB Type-C. So, When USB C-type connector is attached for DP Alt mode,
>> Maybe, you can set the following two state of connector and one property:
>> - extcon_set_cable_state(edev, [EXTCON_USB or EXTCON_USB_HOST], 1);
>> - extcon_set_cable_state(edev, EXTCON_DISP_DP, 1);
>> - extcon_set_cable_state(edev, [EXTCON_USB or EXTCON_USB_HOST], EXTCON_PROP_TYPEC_POLARITY, 0 or 1);
>>
>> Thanks,
>> Chanwoo Choi
> 
> There are 4 modes for Type-C DP alt mode:
> 1) USB host only  :
> 
> extcon_set_cable_state(edev, EXTCON_USB_HOST, 1);
> extcon_set_cable_state(edev, EXTCON_USB, 0);
> extcon_set_cable_state(edev, EXTCON_DISP_DP, 0);
> 
> 2) USB device only
> 
> extcon_set_cable_state(edev, EXTCON_USB_HOST, 0);
> extcon_set_cable_state(edev, EXTCON_USB, 1);
> extcon_set_cable_state(edev, EXTCON_DISP_DP, 0);
> 
> 3) DP only
> 
> extcon_set_cable_state(edev, EXTCON_USB_HOST, 0);
> extcon_set_cable_state(edev, EXTCON_USB, 0);
> extcon_set_cable_state(edev, EXTCON_DISP_DP, 1);
> 
> 4) USB + DP
> 
> extcon_set_cable_state(edev, EXTCON_USB_HOST, 1);
> extcon_set_cable_state(edev, EXTCON_USB, 0);
> extcon_set_cable_state(edev, EXTCON_DISP_DP, 1);
> 
> 
> for 3rd mode: DP only, there is only EXTCON_DISP_DP is attached, the EXTCON_USB_HOST
> and EXTCON_USB are detached, Can I set the property into these 2 detached cable?
> or just call extcon_set_cable_state(edev, EXTCON_DISP_DP, EXTCON_PROP_TYPEC_POLARITY, 0 or 1);

I'm thinking to solve this issue. In result, we can add one more type to specific connector.
For EXTCON_DISP_DP, we can add the two type as following. And EXTCON_PROP_TYPEC_POLARITY property
should be added to EXTCON_TYPE_USB.

+	[EXTCON_DISP_DP] = {
+		.type = EXTCON_TYPE_DISP | EXTCON_TYPE_USB,
+		.id = EXTCON_DISP_DP,
+		.name = "DP",
+	},

So, as you mentioned, EXTCON_DISP_DP can set the EXTCON_PROP_TYPEC_POLARITY property as following:
- extcon_set_cable_state(edev, EXTCON_DISP_DP, EXTCON_PROP_TYPEC_POLARITY, 0 or 1);

I'll again developing the extcon property.

Thanks,
Chanwoo Choi