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Message-ID: <c5c6903d-ec7d-6218-35d3-2ac6caa9d2c5@xs4all.nl>
Date:   Tue, 14 Jun 2022 17:47:49 +0200
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Subject: Re: [PATCH v8 14/17] media: hantro: Stop using Hantro dedicated
 control
Content-Language: en-US
To:     Nicolas Dufresne <nicolas.dufresne@collabora.com>,
        Benjamin Gaignard <benjamin.gaignard@collabora.com>,
        mchehab@kernel.org, ezequiel@vanguardiasur.com.ar,
        p.zabel@pengutronix.de, gregkh@linuxfoundation.org,
        mripard@kernel.org, paul.kocialkowski@bootlin.com, wens@csie.org,
        jernej.skrabec@gmail.com, samuel@sholland.org,
        andrzej.p@collabora.com
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-rockchip@lists.infradead.org, linux-staging@lists.linux.dev,
        linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev,
        kernel@collabora.com
References: <20220614083614.240641-1-benjamin.gaignard@collabora.com>
 <20220614083614.240641-15-benjamin.gaignard@collabora.com>
 <b244e86d-06de-7423-d0df-e77485ce4c87@xs4all.nl>
 <958ab30f9cfbb14e4a7ea55826064e6a20d5ffd2.camel@collabora.com>
From:   Hans Verkuil <hverkuil@xs4all.nl>
In-Reply-To: <958ab30f9cfbb14e4a7ea55826064e6a20d5ffd2.camel@collabora.com>
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On 6/14/22 17:43, Nicolas Dufresne wrote:
> Le mardi 14 juin 2022 à 15:58 +0200, Hans Verkuil a écrit :
>> On 6/14/22 10:36, Benjamin Gaignard wrote:
>>> The number of bits to skip in the slice header can be computed
>>> in the driver by using sps, pps and decode_params information.
>>> This allow to remove Hantro dedicated control.
>>
>> allow -> makes it possible
>>
>>>
>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>>> ---
>>>  drivers/staging/media/hantro/hantro_drv.c     | 36 -----------
>>>  .../staging/media/hantro/hantro_g2_hevc_dec.c | 62 ++++++++++++++++++-
>>>  include/media/hevc-ctrls.h                    | 13 ----
>>>  3 files changed, 61 insertions(+), 50 deletions(-)
>>>
>>> diff --git a/drivers/staging/media/hantro/hantro_drv.c b/drivers/staging/media/hantro/hantro_drv.c
>>> index 536c8c374952..5aac3a090480 100644
>>> --- a/drivers/staging/media/hantro/hantro_drv.c
>>> +++ b/drivers/staging/media/hantro/hantro_drv.c
>>> @@ -304,26 +304,6 @@ static int hantro_jpeg_s_ctrl(struct v4l2_ctrl *ctrl)
>>>  	return 0;
>>>  }
>>>  
>>> -static int hantro_hevc_s_ctrl(struct v4l2_ctrl *ctrl)
>>> -{
>>> -	struct hantro_ctx *ctx;
>>> -
>>> -	ctx = container_of(ctrl->handler,
>>> -			   struct hantro_ctx, ctrl_handler);
>>> -
>>> -	vpu_debug(1, "s_ctrl: id = %d, val = %d\n", ctrl->id, ctrl->val);
>>> -
>>> -	switch (ctrl->id) {
>>> -	case V4L2_CID_HANTRO_HEVC_SLICE_HEADER_SKIP:
>>> -		ctx->hevc_dec.ctrls.hevc_hdr_skip_length = ctrl->val;
>>> -		break;
>>> -	default:
>>> -		return -EINVAL;
>>> -	}
>>> -
>>> -	return 0;
>>> -}
>>> -
>>>  static const struct v4l2_ctrl_ops hantro_ctrl_ops = {
>>>  	.try_ctrl = hantro_try_ctrl,
>>>  };
>>> @@ -332,10 +312,6 @@ static const struct v4l2_ctrl_ops hantro_jpeg_ctrl_ops = {
>>>  	.s_ctrl = hantro_jpeg_s_ctrl,
>>>  };
>>>  
>>> -static const struct v4l2_ctrl_ops hantro_hevc_ctrl_ops = {
>>> -	.s_ctrl = hantro_hevc_s_ctrl,
>>> -};
>>> -
>>>  #define HANTRO_JPEG_ACTIVE_MARKERS	(V4L2_JPEG_ACTIVE_MARKER_APP0 | \
>>>  					 V4L2_JPEG_ACTIVE_MARKER_COM | \
>>>  					 V4L2_JPEG_ACTIVE_MARKER_DQT | \
>>> @@ -487,18 +463,6 @@ static const struct hantro_ctrl controls[] = {
>>>  		.cfg = {
>>>  			.id = V4L2_CID_STATELESS_HEVC_SCALING_MATRIX,
>>>  		},
>>> -	}, {
>>> -		.codec = HANTRO_HEVC_DECODER,
>>> -		.cfg = {
>>> -			.id = V4L2_CID_HANTRO_HEVC_SLICE_HEADER_SKIP,
>>> -			.name = "Hantro HEVC slice header skip bytes",
>>> -			.type = V4L2_CTRL_TYPE_INTEGER,
>>> -			.min = 0,
>>> -			.def = 0,
>>> -			.max = 0x100,
>>> -			.step = 1,
>>> -			.ops = &hantro_hevc_ctrl_ops,
>>> -		},
>>>  	}, {
>>>  		.codec = HANTRO_VP9_DECODER,
>>>  		.cfg = {
>>> diff --git a/drivers/staging/media/hantro/hantro_g2_hevc_dec.c b/drivers/staging/media/hantro/hantro_g2_hevc_dec.c
>>> index d28653d04d20..3be8d6e60bf0 100644
>>> --- a/drivers/staging/media/hantro/hantro_g2_hevc_dec.c
>>> +++ b/drivers/staging/media/hantro/hantro_g2_hevc_dec.c
>>> @@ -117,6 +117,66 @@ static void prepare_tile_info_buffer(struct hantro_ctx *ctx)
>>>  		vpu_debug(1, "%s: no chroma!\n", __func__);
>>>  }
>>>  
>>> +static unsigned int ceil_log2(unsigned int v)
>>> +{
>>> +	/* Compute Ceil(Log2(v))
>>> +	 * Derived from branchless code for integer log2(v) from:
>>> +	 * <http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog>
>>> +	 */
>>> +	unsigned int r, shift;
>>> +
>>> +	v--;
>>> +	r = (v > 0xFFFF) << 4;
>>> +	v >>= r;
>>> +	shift = (v > 0xFF) << 3;
>>> +	v >>= shift;
>>> +	r |= shift;
>>> +	shift = (v > 0xF) << 2;
>>> +	v >>= shift;
>>> +	r |= shift;
>>> +	shift = (v > 0x3) << 1;
>>> +	v >>= shift;
>>> +	r |= shift;
>>> +	r |= (v >> 1);
>>> +
>>> +	return r + 1;
>>> +}
>>
>> Isn't this identical to fls(v - 1)? See also lib/math/reciprocal_div.c
>> where this is used.
> 
> Thanks for pointing this out, I was wondering if there was an equivalent, and
> never knew there was a relation between log2() and the "last set bit". Not sure
> about the -1 here though, can you extend ?

Based on how lib/math/reciprocal_div.c did it. Also, the ceil_log2 function
starts with v--, while fls doesn't. That said, it's wise to verify that that
is correct.

Regards,

	Hans

> 
>>
>> Regards,
>>
>> 	Hans
>>
>>> +
>>> +static int compute_header_skip_lenght(struct hantro_ctx *ctx)
>>> +{
>>> +	const struct hantro_hevc_dec_ctrls *ctrls = &ctx->hevc_dec.ctrls;
>>> +	const struct v4l2_ctrl_hevc_decode_params *decode_params = ctrls->decode_params;
>>> +	const struct v4l2_ctrl_hevc_sps *sps = ctrls->sps;
>>> +	const struct v4l2_ctrl_hevc_pps *pps = ctrls->pps;
>>> +	int skip = 0;
>>> +
>>> +	if (pps->flags & V4L2_HEVC_PPS_FLAG_OUTPUT_FLAG_PRESENT)
>>> +		/* size of pic_output_flag */
>>> +		skip++;
>>> +
>>> +	if (sps->flags & V4L2_HEVC_SPS_FLAG_SEPARATE_COLOUR_PLANE)
>>> +		/* size of pic_order_cnt_lsb */
>>> +		skip += 2;
>>> +
>>> +	if (!(decode_params->flags & V4L2_HEVC_DECODE_PARAM_FLAG_IDR_PIC)) {
>>> +		/* size of pic_order_cnt_lsb */
>>> +		skip += sps->log2_max_pic_order_cnt_lsb_minus4 + 4;
>>> +
>>> +		/* size of short_term_ref_pic_set_sps_flag */
>>> +		skip++;
>>> +
>>> +		if (decode_params->short_term_ref_pic_set_size)
>>> +			/* size of st_ref_pic_set( num_short_term_ref_pic_sets ) */
>>> +			skip += decode_params->short_term_ref_pic_set_size;
>>> +		else if (sps->num_short_term_ref_pic_sets > 1)
>>> +			skip += ceil_log2(sps->num_short_term_ref_pic_sets);
>>> +
>>> +		skip += decode_params->long_term_ref_pic_set_size;
>>> +	}
>>> +
>>> +	return skip;
>>> +}
>>> +
>>>  static void set_params(struct hantro_ctx *ctx)
>>>  {
>>>  	const struct hantro_hevc_dec_ctrls *ctrls = &ctx->hevc_dec.ctrls;
>>> @@ -134,7 +194,7 @@ static void set_params(struct hantro_ctx *ctx)
>>>  
>>>  	hantro_reg_write(vpu, &g2_output_8_bits, 0);
>>>  
>>> -	hantro_reg_write(vpu, &g2_hdr_skip_length, ctrls->hevc_hdr_skip_length);
>>> +	hantro_reg_write(vpu, &g2_hdr_skip_length, compute_header_skip_lenght(ctx));
>>>  
>>>  	min_log2_cb_size = sps->log2_min_luma_coding_block_size_minus3 + 3;
>>>  	max_log2_ctb_size = min_log2_cb_size + sps->log2_diff_max_min_luma_coding_block_size;
>>> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
>>> index d6cb3779d190..efc0412ac41e 100644
>>> --- a/include/media/hevc-ctrls.h
>>> +++ b/include/media/hevc-ctrls.h
>>> @@ -467,17 +467,4 @@ struct v4l2_ctrl_hevc_scaling_matrix {
>>>  	__u8	scaling_list_dc_coef_32x32[2];
>>>  };
>>>  
>>> -/*  MPEG-class control IDs specific to the Hantro driver as defined by V4L2 */
>>> -#define V4L2_CID_CODEC_HANTRO_BASE				(V4L2_CTRL_CLASS_CODEC | 0x1200)
>>> -/*
>>> - * V4L2_CID_HANTRO_HEVC_SLICE_HEADER_SKIP -
>>> - * the number of data (in bits) to skip in the
>>> - * slice segment header.
>>> - * If non-IDR, the bits to be skipped go from syntax element "pic_output_flag"
>>> - * to before syntax element "slice_temporal_mvp_enabled_flag".
>>> - * If IDR, the skipped bits are just "pic_output_flag"
>>> - * (separate_colour_plane_flag is not supported).
>>> - */
>>> -#define V4L2_CID_HANTRO_HEVC_SLICE_HEADER_SKIP	(V4L2_CID_CODEC_HANTRO_BASE + 0)
>>> -
>>>  #endif
>>
>