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

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Message-ID: <aa3cae53-38bb-e8a8-62df-aeda0272f1f4@aspeedtech.com>
Date:   Wed, 22 Dec 2021 14:10:37 +0800
From:   Jammy Huang <jammy_huang@...eedtech.com>
To:     Joel Stanley <joel@....id.au>
CC:     Eddie James <eajames@...ux.ibm.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Andrew Jeffery <andrew@...id.au>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-aspeed <linux-aspeed@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] media: aspeed: Fix timing polarity incorrect

Hi Joel,

OK, I will update in next patch as you advised.
Thanks for your review.

On 2021/12/22 上午 09:22, Joel Stanley wrote:
> On Fri, 17 Dec 2021 at 09:54, Jammy Huang <jammy_huang@...eedtech.com> wrote:
>> This is a workaround for 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.
>>
>> Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
>> ---
>>   drivers/media/platform/aspeed-video.c | 18 ++++++++++++++++++
>>   1 file changed, 18 insertions(+)
>>
>> diff --git a/drivers/media/platform/aspeed-video.c b/drivers/media/platform/aspeed-video.c
>> index 5ad3a20c5bac..f628f69bb7dd 100644
>> --- a/drivers/media/platform/aspeed-video.c
>> +++ b/drivers/media/platform/aspeed-video.c
>> @@ -989,6 +989,15 @@ static void aspeed_video_get_resolution(struct aspeed_video *video)
>>                  video->frame_top = FIELD_GET(VE_SRC_TB_EDGE_DET_TOP,
>>                                               src_tb_edge);
>>                  det->vsync = FIELD_GET(VE_SYNC_STATUS_VSYNC, sync);
>> +               /*
>> +                * Workaround for polarity detection
>> +                * Use sync(VR098) counts from sync's rising edge till falling
>> +                * edge to tell sync polarity.
>> +                */
>> +               if (det->vsync > (FIELD_GET(VE_MODE_DETECT_V_LINES, mds) >> 1))
> Are you right shifting as this is the value / 2? I think it's clearer
> to write / 2 instead of >> 1.
>
> Mention in the comment that this is a workaround for when the sync
> value is larger than half.
>
>> +                       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 - det->vsync;
>>                          det->vfrontporch =
>> @@ -1010,6 +1019,15 @@ static void aspeed_video_get_resolution(struct aspeed_video *video)
>>                  video->frame_left = FIELD_GET(VE_SRC_LR_EDGE_DET_LEFT,
>>                                                src_lr_edge);
>>                  det->hsync = FIELD_GET(VE_SYNC_STATUS_HSYNC, sync);
>> +               /*
>> +                * Workaround for polarity detection
>> +                * Use sync(VR098) counts from sync's rising edge till falling
>> +                * edge to tell sync polarity.
>> +                */
>> +               if (det->hsync > (htotal >> 1))
>> +                       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 - det->hsync;
>>                          det->hfrontporch = htotal - video->frame_right;
>> --
>> 2.25.1
>>
-- 
Best Regards
Jammy