linux-kernel - Re: [PATCH v2 4/4] media: aspeed: Fix timing polarity incorrect

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Message-ID: <fbe1742c-2afd-bc09-b565-783b080a1418@aspeedtech.com>
Date:   Tue, 25 Jan 2022 09:37:51 +0800
From:   Jammy Huang <jammy_huang@...eedtech.com>
To:     Hans Verkuil <hverkuil@...all.nl>,
        "eajames@...ux.ibm.com" <eajames@...ux.ibm.com>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "joel@....id.au" <joel@....id.au>,
        "andrew@...id.au" <andrew@...id.au>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/4] media: aspeed: Fix timing polarity incorrect


On 2022/1/24 下午 06:22, Hans Verkuil wrote:
> On 24/01/2022 03:29, Jammy Huang wrote:
>> On 2022/1/21 下午 03:30, Hans Verkuil wrote:
>>> On 12/22/21 09:21, Jammy Huang wrote:
>>>> This is a workaround for sync polarity unstable.
>>>> Sync value get by VR09C counts from sync's rising edge, which means
>>>> sync's polarity is negative if sync value is bigger than total/2.
>>> Do you have an example of such a format, or is this mostly theoretical?
>>>
>>> Either provide the example or make a note that it is theoretical.
>> OK, I will update an example in next patch. Let me explain first.
>>
>> This is a must-be result. Please refer to the graph below as I sent in 3/4 of this
>> series. For negative sync, sync width equals to back porch + data enable + front porch.
>> Thus, sync would be bigger than 90% of total in most cases.
> Right, I suspected that might be the case.
>
> I think it would be better to combine patches 3 and 4 into a single
> patch, since they are closely related and it is actually easier to
> understand if it's just a single patch.
OK, I will combine 3/4 into a single patch in next series.
Thanks.

Best Regards,

         Jammy
>
> Regards,
>
> 	Hans
>
>>                    +-------------------+
>>                    |    v i d e o      |
>>        +--+  +-----+                   +-----+  +---+
>>           |  |                               |  |
>>           +--+                               +--+
>>         vsync+-------------------------------+
>>     frame_top+-----+
>> frame_bottom+-------------------------+
>>
>>
>> Following registers are what I got for 1920x1200@60.
>>
>> 1e700090: 07ee206f 04c9001a c4d3efff 04cc001f
>>
>> 1e7000a0: 0000081f 00000000 00000000 00000000
>>
>> vertical total = 0x4D3 (VR098[27:16]) = 1235
>> vertical sync = 0x4CC (VR09C[27:16]) = 1228
>>
>>> Regards,
>>>
>>>      Hans
>>>
>>>> Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
>>>> ---
>>>>    v2:
>>>>     - Use 'total/2' rather than 'total<<1'
>>>>     - Update comment
>>>> ---
>>>>    drivers/media/platform/aspeed-video.c | 20 ++++++++++++++++++++
>>>>    1 file changed, 20 insertions(+)
>>>>
>>>> diff --git a/drivers/media/platform/aspeed-video.c b/drivers/media/platform/aspeed-video.c
>>>> index 7c50567f5ab0..c3e3343d91e1 100644
>>>> --- a/drivers/media/platform/aspeed-video.c
>>>> +++ b/drivers/media/platform/aspeed-video.c
>>>> @@ -989,6 +989,16 @@ static void aspeed_video_get_resolution(struct aspeed_video *video)
>>>>              video->frame_bottom = FIELD_GET(VE_SRC_TB_EDGE_DET_BOT, src_tb_edge);
>>>>            video->frame_top = FIELD_GET(VE_SRC_TB_EDGE_DET_TOP, src_tb_edge);
>>>> +
>>>> +        /*
>>>> +         * This is a workaround for polarity detection when the sync
>>>> +         * value is larger than half.
>>>> +         */
>>>> +        if (vsync > (vtotal / 2))
>>>> +            det->polarities &= ~V4L2_DV_VSYNC_POS_POL;
>>>> +        else
>>>> +            det->polarities |= V4L2_DV_VSYNC_POS_POL;
>>>> +
>>>>            if (det->polarities & V4L2_DV_VSYNC_POS_POL) {
>>>>                det->vbackporch = video->frame_top - vsync;
>>>>                det->vfrontporch = vtotal - video->frame_bottom;
>>>> @@ -1003,6 +1013,16 @@ static void aspeed_video_get_resolution(struct aspeed_video *video)
>>>>              video->frame_right = FIELD_GET(VE_SRC_LR_EDGE_DET_RT, src_lr_edge);
>>>>            video->frame_left = FIELD_GET(VE_SRC_LR_EDGE_DET_LEFT, src_lr_edge);
>>>> +
>>>> +        /*
>>>> +         * This is a workaround for polarity detection when the sync
>>>> +         * value is larger than half.
>>>> +         */
>>>> +        if (hsync > (htotal / 2))
>>>> +            det->polarities &= ~V4L2_DV_HSYNC_POS_POL;
>>>> +        else
>>>> +            det->polarities |= V4L2_DV_HSYNC_POS_POL;
>>>> +
>>>>            if (det->polarities & V4L2_DV_HSYNC_POS_POL) {
>>>>                det->hbackporch = video->frame_left - hsync;
>>>>                det->hfrontporch = htotal - video->frame_right;