linux-kernel - Re: [PATCH] v4l: vsp1: Fix continuous mode for dual pipelines

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Date:   Fri, 9 Feb 2018 14:53:46 +0000
From:   Kieran Bingham <kieran.bingham@...asonboard.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     mchehab@...nel.org, linux-media@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        "Stable v4.14+" <stable@...r.kernel.org>
Subject: Re: [PATCH] v4l: vsp1: Fix continuous mode for dual pipelines

Hi Laurent,

On 09/02/18 13:27, Laurent Pinchart wrote:
> Hi Kieran,
> 
> Thank you for the patch.
> 
> On Friday, 9 February 2018 15:18:25 EET Kieran Bingham wrote:
>> From: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
>>
>> To allow dual pipelines utilising two WPF entities when available, the
>> VSP was updated to support header-mode display list in continuous
>> pipelines.
>>
>> A small bug in the status check of the command register causes the
>> second pipeline to be directly afflicted by the running of the first;
>> appearing as a perceived performance issue with stuttering display.
>>
>> Fix the vsp1_dl_list_hw_update_pending() call to ensure that the read
>> comparison corresponds to the correct pipeline.
>>
>> Fixes: eaf4bfad6ad8 ("v4l: vsp1: Add support for header display
>> lists in continuous mode")
>> Cc: "Stable v4.14+" <stable@...r.kernel.org>
>>
>> Signed-off-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> 
> Good catch !
> 
> The patch looks good to me, but I wonder if we shouldn't write the subject 
> line as "v4l: vsp1: Fix header display list status check in continuous mode". 

I'm fine with that,

Will resend with your RB tag.


> Sure, we're fixing continuous mode for dual pipelines, but that's more of a 
> side effect, it's header display lists that are broken as a whole in 
> continuous mode, even if we only use that for dual pipelines right now.
> 
> Apart from that,
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> 
> Please let me know if you'd like to rewrite the commit message.
> 
>> ---
>>  drivers/media/platform/vsp1/vsp1_dl.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/platform/vsp1/vsp1_dl.c
>> b/drivers/media/platform/vsp1/vsp1_dl.c index 8cd03ee45f79..34b5ed2592f8
>> 100644
>> --- a/drivers/media/platform/vsp1/vsp1_dl.c
>> +++ b/drivers/media/platform/vsp1/vsp1_dl.c
>> @@ -509,7 +509,8 @@ static bool vsp1_dl_list_hw_update_pending(struct
>> vsp1_dl_manager *dlm) return !!(vsp1_read(vsp1, VI6_DL_BODY_SIZE)
>>  			  & VI6_DL_BODY_SIZE_UPD);
>>  	else
>> -		return !!(vsp1_read(vsp1, VI6_CMD(dlm->index) & VI6_CMD_UPDHDR));
>> +		return !!(vsp1_read(vsp1, VI6_CMD(dlm->index))
>> +			  & VI6_CMD_UPDHDR);
> 
> /me feels so ashamed.

Bah, it's only a brace out of place. I mean, what harm could it do ... hehe :-)

Personally I still blame the compiler for not picking up on the fact that we
told it to do something we didn't want it to do.

/me ducks to avoid all the items thrown by the compiler guys...

>>  }
>>
>>  static bool vsp1_dl_hw_active(struct vsp1_dl_manager *dlm)

--
Kieran