Re: [PATCH] media: staging: ipu3-imgu: Initialise height_per_slice in the stripes

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Bingbu,

On Thu, Sep 23, 2021 at 10:29:33AM +0000, Cao, Bingbu wrote:
> On Thursday, September 23, 2021 5:46 PM, Laurent Pinchart wrote:
> > On Thu, Sep 23, 2021 at 09:06:32AM +0000, Cao, Bingbu wrote:
> > > Jean-Michel,
> > >
> > > Firstly, the .height_per_slice could be 0 if your .grid.width larger
> > > than 32.
> > 
> > Which .height_per_slice are you talking about ? A field of that name
> > exists in both ipu3_uapi_acc_param.awb.config.grid and struct
> > ipu3_uapi_grid_config and imgu_abi_awb_config.stripes.grid.
> > 
> > They are both computed by the driver, in imgu_css_cfg_acc(). The former
> > is set to
> > 
> > 	acc->awb.config.grid.height_per_slice =
> > 		IMGU_ABI_AWB_MAX_CELLS_PER_SET / acc->awb.config.grid.width,
> > 
> > IMGU_ABI_AWB_MAX_CELLS_PER_SET is equal to 160, so it can only be 0 if
> > grid.width > 160, which is invalid.
> 
> For awb_fr and af, it could be 0 if the .config.grid_cfg.width > 32.

Indeed, my bad. I was focussing on the AWB statistics.

What are the implications of a height_per_slice value of 0 ?

While we are on this topic, what is a "slice" ? Does it matter for the
user, as in does it have an impact on the statistics values, or on how
they're arranged in memory, or is it an implementation detail of the
firmware that has no consequence on what can be seen by the user ? (The
"user" here is the code that reads the statistics in userspace).

> > > From your configuration, looks like something wrong in the stripe
> > > configuration cause not entering the 2 stripes branch.
> > 
> > Why is that ? Isn't it valid for a grid configuration to use a single
> > stripe, if the image is small enough, or if the grid only covers the left
> > part of the image ?
> > 
> > > On Wednesday, September 22, 2021 1:54 PM, Jean-Michel Hautbois wrote:
> > > > On 22/09/2021 06:33, Cao, Bingbu wrote:
> > > > > Jean-Michel,
> > > > >
> > > > > Thanks for you patch.
> > > > > What is the value of .config.grid_cfg.width for your low resolutions?
> > > >
> > > > I don't know if a 1920x1280 output is a low resolution, but the grid
> > > > is configured as:
> > > > - grid_cfg.width = 79
> > > > - grid_cfg.height = 24
> > > > - grid_cfg.block_width_log2 = 4
> > > > - grid_cfg.block_height_log2 = 6
> > > >
> > > > Here is a full debug output of the AWB part in imgu_css_cfg_acc():
> > > >
> > > > acc->stripe.down_scaled_stripes[0].width: 1280
> > > > acc->stripe.down_scaled_stripes[0].height: 1536
> > > > acc->stripe.down_scaled_stripes[0].offset: 0
> > > > acc->stripe.bds_out_stripes[0].width: 1280
> > > > acc->stripe.bds_out_stripes[0].height: 1536
> > > > acc->stripe.bds_out_stripes[0].offset: 0
> > > > acc->acc->awb.stripes[0].grid.width: 79
> > > > acc->awb.stripes[0].grid.block_width_log2: 4
> > > > acc->acc->awb.stripes[0].grid.height: 24
> > > > acc->awb.stripes[0].grid.block_height_log2: 6
> > > > acc->awb.stripes[0].grid.x_start: 0
> > > > acc->awb.stripes[0].grid.x_end: 1263
> > > > acc->awb.stripes[0].grid.y_start: 0
> > > > acc->awb.stripes[0].grid.y_end: 1535
> > > > acc->stripe.down_scaled_stripes[1].width: 1280
> > > > acc->stripe.down_scaled_stripes[1].height: 1536
> > > > acc->stripe.down_scaled_stripes[1].offset: 1024
> > > > acc->stripe.bds_out_stripes[1].width: 1280
> > > > acc->stripe.bds_out_stripes[1].height: 1536
> > > > acc->stripe.bds_out_stripes[1].offset: 1024
> > > > acc->acc->awb.stripes[1].grid.width: 79
> > > > acc->awb.stripes[1].grid.block_width_log2: 4
> > > > acc->acc->awb.stripes[1].grid.height: 24
> > > > acc->awb.stripes[1].grid.block_height_log2: 6
> > > > acc->awb.stripes[1].grid.x_start: 0
> > > > acc->awb.stripes[1].grid.x_end: 1263
> > > > acc->awb.stripes[1].grid.y_start: 0
> > > > acc->awb.stripes[1].grid.y_end: 1535
> 
> Are these dumps from 1920x1280 output?

Jean-Michel, could you comment on this ?

Note that the grid is configured with 79 cells of 16 pixels, covering
1264 pixels horizontally. That's not the full image for a 1920 pixels
output, and will probably not be done in practice, but there's nothing
preventing the grid from covering part of the image only.

> > > > This has been outputted with: https://paste.debian.net/1212791/
> > > >
> > > > The examples I gave before were 1280x720 output and not 1920x1080,
> > > > here are they:
> > > > - without the patch: https://pasteboard.co/hHo4QkVUSk8e.png
> > > > - with the patch: https://pasteboard.co/YUGUvS5tD0bo.png
> > > >
> > > > As you can see we have the same behaviour.
> > > >
> > > > > On Tuesday, September 21, 2021 10:34 PM, Laurent Pinchart wrote:
> > > > >> On Tue, Sep 21, 2021 at 03:04:37PM +0200, Jean-Michel Hautbois wrote:
> > > > >>> On 21/09/2021 13:07, Sakari Ailus wrote:
> > > > >>>> On Thu, Sep 16, 2021 at 07:25:04PM +0200, Jean-Michel Hautbois wrote:
> > > > >>>>> While playing with low resolutions for the grid, it appeared
> > > > >>>>> that height_per_slice is not initialised if we are not using
> > > > >>>>> both stripes for the calculations. This pattern occurs three times:
> > > > >>>>> - for the awb_fr processing block
> > > > >>>>> - for the af processing block
> > > > >>>>> - for the awb processing block
> > > > >>>>>
> > > > >>>>> The idea of this small portion of code is to reduce complexity
> > > > >>>>> in loading the statistics, it could be done also when only one
> > > > >>>>> stripe is used. Fix it by getting this initialisation code
> > > > >>>>> outside of the
> > > > >>>>> else() test case.
> > > > >>>>>
> > > > >>>>> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
> > > > >>>>> ---
> > > > >>>>>  drivers/staging/media/ipu3/ipu3-css-params.c | 44 >>>>> ++++++++++----------
> > > > >>>>>  1 file changed, 22 insertions(+), 22 deletions(-)
> > > > >>>>>
> > > > >>>>> diff --git a/drivers/staging/media/ipu3/ipu3-css-params.c
> > > > >>>>> b/drivers/staging/media/ipu3/ipu3-css-params.c
> > > > >>>>> index e9d6bd9e9332..05da7dbdca78 100644
> > > > >>>>> --- a/drivers/staging/media/ipu3/ipu3-css-params.c
> > > > >>>>> +++ b/drivers/staging/media/ipu3/ipu3-css-params.c
> > > > >>>>> @@ -2428,16 +2428,16 @@ int imgu_css_cfg_acc(struct imgu_css *css, unsigned int pipe,
> > > > >>>>>  					acc->awb_fr.stripes[1].grid_cfg.width,
> > > > >>>>>  					b_w_log2);
> > > > >>>>>  		acc->awb_fr.stripes[1].grid_cfg.x_end = end;
> > > > >>>>> -
> > > > >>>>> -		/*
> > > > >>>>> -		 * To reduce complexity of debubbling and loading
> > > > >>>>> -		 * statistics fix grid_height_per_slice to 1 for both
> > > > >>>>> -		 * stripes.
> > > > >>>>> -		 */
> > > > >>>>> -		for (i = 0; i < stripes; i++)
> > > > >>>>> -			acc->awb_fr.stripes[i].grid_cfg.height_per_slice = 1;
> > > > >>>>>  	}
> > > > >>>>>
> > > > >>>>> +	/*
> > > > >>>>> +	 * To reduce complexity of debubbling and loading
> > > > >>>>> +	 * statistics fix grid_height_per_slice to 1 for both
> > > > >>>>> +	 * stripes.
> > > > >>>>> +	 */
> > > > >>>>> +	for (i = 0; i < stripes; i++)
> > > > >>>>> +		acc->awb_fr.stripes[i].grid_cfg.height_per_slice = 1;
> > > > >>>>> +
> > > > >>>>>  	if (imgu_css_awb_fr_ops_calc(css, pipe, &acc->awb_fr))
> > > > >>>>>  		return -EINVAL;
> > > > >>>>>
> > > > >>>>> @@ -2591,15 +2591,15 @@ int imgu_css_cfg_acc(struct imgu_css *css, unsigned int pipe,
> > > > >>>>>  			imgu_css_grid_end(acc->af.stripes[1].grid_cfg.x_start,
> > > > >>>>>  					  acc->af.stripes[1].grid_cfg.width,
> > > > >>>>>  					  b_w_log2);
> > > > >>>>> -
> > > > >>>>> -		/*
> > > > >>>>> -		 * To reduce complexity of debubbling and loading statistics
> > > > >>>>> -		 * fix grid_height_per_slice to 1 for both stripes
> > > > >>>>> -		 */
> > > > >>>>> -		for (i = 0; i < stripes; i++)
> > > > >>>>> -			acc->af.stripes[i].grid_cfg.height_per_slice = 1;
> > > > >>>>>  	}
> > > > >>>>>
> > > > >>>>> +	/*
> > > > >>>>> +	 * To reduce complexity of debubbling and loading statistics
> > > > >>>>> +	 * fix grid_height_per_slice to 1 for both stripes
> > > > >>>>> +	 */
> > > > >>>>> +	for (i = 0; i < stripes; i++)
> > > > >>>>> +		acc->af.stripes[i].grid_cfg.height_per_slice = 1;
> > > > >>>>> +
> > > > >>>>>  	if (imgu_css_af_ops_calc(css, pipe, &acc->af))
> > > > >>>>>  		return -EINVAL;
> > > > >>>>>
> > > > >>>>> @@ -2660,15 +2660,15 @@ int imgu_css_cfg_acc(struct imgu_css *css, unsigned int pipe,
> > > > >>>>>  			imgu_css_grid_end(acc->awb.stripes[1].grid.x_start,
> > > > >>>>>  					  acc->awb.stripes[1].grid.width,
> > > > >>>>>  					  b_w_log2);
> > > > >>>>> -
> > > > >>>>> -		/*
> > > > >>>>> -		 * To reduce complexity of debubbling and loading statistics
> > > > >>>>> -		 * fix grid_height_per_slice to 1 for both stripes
> > > > >>>>> -		 */
> > > > >>>>> -		for (i = 0; i < stripes; i++)
> > > > >>>>> -			acc->awb.stripes[i].grid.height_per_slice = 1;
> > > > >>>>>  	}
> > > > >>>>>
> > > > >>>>> +	/*
> > > > >>>>> +	 * To reduce complexity of debubbling and loading statistics
> > > > >>>>> +	 * fix grid_height_per_slice to 1 for both stripes
> > > > >>>>> +	 */
> > > > >>>>> +	for (i = 0; i < stripes; i++)
> > > > >>>>> +		acc->awb.stripes[i].grid.height_per_slice = 1;
> > > > >>>>> +
> > > > >>>>>  	if (imgu_css_awb_ops_calc(css, pipe, &acc->awb))
> > > > >>>>>  		return -EINVAL;
> > > > >>>>>
> > > > >>>>
> > > > >>>> While it seems like a sensible idea to initialise arguments to
> > > > >>>> firmware, does this have an effect on the statistics format? If
> > > > >>>> so, can the existing user space cope with that?
> > > > >>>
> > > > >>> To try and figure that out, we have tested several grid
> > > > >>> configurations and inspected the captured statistics. We have
> > > > >>> converted the statistics in an image, rendering each cell as a
> > > > >>> pixel whose red, green and blue components are the cell's red, green and blue averages.
> > > > >>> This turned out to be a very effectice tool to quickly visualize
> > > > >>> AWB statistics.
> > > > >>> We have made a lot of tests with different output resolutions,
> > > > >>> from a small one up to the full-scale one.
> > > > >>>
> > > > >>> Here is one example of a statistics output with a ViewFinder
> > > > >>> configured as 1920x1280, with a BDS output configuration set to
> > > > >>> 2304x1536 (sensor is 2592x1944).
> > > > >>>
> > > > >>> Without the patch, configuring a 79x45 grid of 16x16 cells we
> > > > >>> obtain the
> > > > >>> image: https://pasteboard.co/g4nC4fHjbVER.png.
> > > > >>> We can notice a weird padding every two lines and it seems to be
> > > > >>> missing half of the frame.
> > > > >>>
> > > > >>> With the patch applied, the same configuration gives us the image:
> > > > >>> https://pasteboard.co/rzap6axIvVdu.png
> > > > >>>
> > > > >>> We can clearly see the one padding pixel on the right, and the
> > > > >>> frame is all there, as expected.
> > > > >>>
> > > > >>> Tomasz: We're concerned that this patch may have an impact on
> > > > >>> the ChromeOS Intel Camera HAL with the IPU3. Is it possible for
> > > > >>> someone to review and test this please?
> > > > >>
> > > > >> As shown by the images above, this is a real fix. It only affects
> > > > >> grid configurations that use a single stripe (left or right), so
> > > > >> either "small" resolutions (less than 1280 pixels at the BDS
> > > > >> output if I recall correctly), or grid configurations that span
> > > > >> the left part of the image with higher resolutions. The latter is
> > > > >> probably unlikely. For the former, it may affect the binary
> > > > >> library, especially if it includes a workaround for the bug.
> > > > >>
> > > > >> Still, this change is good I believe, so it should be upstreamed.

-- 
Regards,

Laurent Pinchart