Re: [RFC PATCH 4/4] staging: media: omap4iss: use v4l2_get_link_freq() to get the external rate

[Andrey Konovalov <andrey.konovalov@linaro.org>]

Hi Sakari,

On 05.03.2021 18:41, Sakari Ailus wrote:
> Hi Andrey,
> 
> Thanks for the set.
> 
> On Wed, Mar 03, 2021 at 09:08:17PM +0300, Andrey Konovalov wrote:
>> This driver uses V4L2_CID_PIXEL_RATE to calculate the CSI2 link frequency,
>> but this may give incorrect result in some cases. Use v4l2_get_link_freq()
>> instead.
>>
>> Also the driver used the external_rate field in struct iss_pipeline as a
>> flag to prevent excessive v4l2_subdev_call's when processing the frames
>> in single-shot mode. Replace the external_rate with external_lfreq, and
>> use external_bpp and external_lfreq to call v4l2_subdev_call(get_fmt) and
>> v4l2_get_link_freq() respectively only once per iss_video_streamon().
>>
>> Signed-off-by: Andrey Konovalov <andrey.konovalov@linaro.org>
>> ---
>>   drivers/staging/media/omap4iss/iss.c        | 12 +-----------
>>   drivers/staging/media/omap4iss/iss_csiphy.c | 19 ++++++++++++++++---
>>   drivers/staging/media/omap4iss/iss_video.c  |  2 +-
>>   drivers/staging/media/omap4iss/iss_video.h  |  2 +-
>>   4 files changed, 19 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/staging/media/omap4iss/iss.c b/drivers/staging/media/omap4iss/iss.c
>> index dae9073e7d3c..0eb7b1b5dcc4 100644
>> --- a/drivers/staging/media/omap4iss/iss.c
>> +++ b/drivers/staging/media/omap4iss/iss.c
>> @@ -131,7 +131,7 @@ int omap4iss_get_external_info(struct iss_pipeline *pipe,
>>   	if (!pipe->external)
>>   		return 0;
>>   
>> -	if (pipe->external_rate)
>> +	if (pipe->external_bpp)
>>   		return 0;
>>   
>>   	memset(&fmt, 0, sizeof(fmt));
>> @@ -145,16 +145,6 @@ int omap4iss_get_external_info(struct iss_pipeline *pipe,
>>   
>>   	pipe->external_bpp = omap4iss_video_format_info(fmt.format.code)->bpp;
>>   
>> -	ctrl = v4l2_ctrl_find(pipe->external->ctrl_handler,
>> -			      V4L2_CID_PIXEL_RATE);
>> -	if (!ctrl) {
>> -		dev_warn(iss->dev, "no pixel rate control in subdev %s\n",
>> -			 pipe->external->name);
>> -		return -EPIPE;
>> -	}
>> -
>> -	pipe->external_rate = v4l2_ctrl_g_ctrl_int64(ctrl);
>> -
>>   	return 0;
>>   }
>>   
>> diff --git a/drivers/staging/media/omap4iss/iss_csiphy.c b/drivers/staging/media/omap4iss/iss_csiphy.c
>> index 96f2ce045138..cec0cd21f7e0 100644
>> --- a/drivers/staging/media/omap4iss/iss_csiphy.c
>> +++ b/drivers/staging/media/omap4iss/iss_csiphy.c
>> @@ -119,6 +119,7 @@ int omap4iss_csiphy_config(struct iss_device *iss,
>>   	struct iss_pipeline *pipe = to_iss_pipeline(&csi2_subdev->entity);
>>   	struct iss_v4l2_subdevs_group *subdevs = pipe->external->host_priv;
>>   	struct iss_csiphy_dphy_cfg csi2phy;
>> +	s64 link_freq;
>>   	int csi2_ddrclk_khz;
>>   	struct iss_csiphy_lanes_cfg *lanes;
>>   	unsigned int used_lanes = 0;
>> @@ -193,9 +194,21 @@ int omap4iss_csiphy_config(struct iss_device *iss,
>>   	if (lanes->clk.pos == 0 || used_lanes & (1 << lanes->clk.pos))
>>   		return -EINVAL;
>>   
>> -	csi2_ddrclk_khz = pipe->external_rate / 1000
>> -		/ (2 * csi2->phy->used_data_lanes)
>> -		* pipe->external_bpp;
>> +	if (!pipe->external_lfreq) {
>> +		link_freq = v4l2_get_link_freq(pipe->external->ctrl_handler,
> 
> I wonder if you could this unconditionally, and remove external_lfreq field
> altogether. The same could be done for external_bpp but that's out of scope
> for this patch.

Hard to tell.
This might be possible as all this logic to prevent multiple v4l2_subdev_call(get_fmt)
and v4l2_get_link_freq() calls per single iss_video_streamon() seems to be needed
only when ISS operates in memory-to-memory mode. Not sure how link frequency, and
used_lanes are related to memory-to-memory mode... Will try to find out.

Thanks,
Andrey

>> +					       pipe->external_bpp,
>> +					       2 * csi2->phy->used_data_lanes);
>> +		if (link_freq < 0) {
>> +			dev_warn(iss->dev,
>> +				 "failed to read the link frequency fromn subdev %s\n",
>> +				 pipe->external->name);
>> +			return -EINVAL;
>> +		}
>> +
>> +		pipe->external_lfreq = link_freq;
>> +	}
>> +
>> +	csi2_ddrclk_khz = div_s64(pipe->external_lfreq, 1000);
>>   
>>   	/*
>>   	 * THS_TERM: Programmed value = ceil(12.5 ns/DDRClk period) - 1.
>> diff --git a/drivers/staging/media/omap4iss/iss_video.c b/drivers/staging/media/omap4iss/iss_video.c
>> index 66975a37dc85..a654c8d18bbc 100644
>> --- a/drivers/staging/media/omap4iss/iss_video.c
>> +++ b/drivers/staging/media/omap4iss/iss_video.c
>> @@ -872,7 +872,7 @@ iss_video_streamon(struct file *file, void *fh, enum v4l2_buf_type type)
>>   	pipe = entity->pipe
>>   	     ? to_iss_pipeline(entity) : &video->pipe;
>>   	pipe->external = NULL;
>> -	pipe->external_rate = 0;
>> +	pipe->external_lfreq = 0;
>>   	pipe->external_bpp = 0;
>>   
>>   	ret = media_entity_enum_init(&pipe->ent_enum, entity->graph_obj.mdev);
>> diff --git a/drivers/staging/media/omap4iss/iss_video.h b/drivers/staging/media/omap4iss/iss_video.h
>> index 526281bf0051..2ad5c8483958 100644
>> --- a/drivers/staging/media/omap4iss/iss_video.h
>> +++ b/drivers/staging/media/omap4iss/iss_video.h
>> @@ -86,7 +86,7 @@ struct iss_pipeline {
>>   	bool error;
>>   	struct v4l2_fract max_timeperframe;
>>   	struct v4l2_subdev *external;
>> -	unsigned int external_rate;
>> +	s64 external_lfreq;
>>   	int external_bpp;
>>   };
>>   
>