media: hantro: Add H.264 field decoding support

This adds the required code to support field decoding. While most of
the code is derived from Rockchip and VSI reference code, the
reduction of the reference list to 16 entries was found by
trial and errors. The list consists of all the references with the
opposite field parity.

The strategy is to deduplicate the reference picture that points
to the same storage (same index). The choice of opposite parity has
been made to keep the other field of the current field pair in the
list. This method may not be robust if a field was lost.

[hverkuil: fix typos in the comment before deduplicate_reflist()]
[hverkuil: document new cur_poc field]

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Author: ndufresne

drivers/staging/media/hantro/hantro_h264.c

@@ -22,6 +22,12 @@
 #define POC_BUFFER_SIZE			34
 #define SCALING_LIST_SIZE		(6 * 16 + 2 * 64)
 
+/*
+ * For valid and long term reference marking, index are reversed, so bit 31
+ * indicates the status of the picture 0.
+ */
+#define REF_BIT(i)			BIT(32 - 1 - (i))
+
 /* Data structure describing auxiliary buffer format. */
 struct hantro_h264_dec_priv_tbl {
 	u32 cabac_table[CABAC_INIT_BUFFER_SIZE];
@@ -227,6 +233,7 @@ static void prepare_table(struct hantro_ctx *ctx)
 {
 	const struct hantro_h264_dec_ctrls *ctrls = &ctx->h264_dec.ctrls;
 	const struct v4l2_ctrl_h264_decode_params *dec_param = ctrls->decode;
+	const struct v4l2_ctrl_h264_sps *sps = ctrls->sps;
 	struct hantro_h264_dec_priv_tbl *tbl = ctx->h264_dec.priv.cpu;
 	const struct v4l2_h264_dpb_entry *dpb = ctx->h264_dec.dpb;
 	u32 dpb_longterm = 0;
@@ -237,20 +244,45 @@ static void prepare_table(struct hantro_ctx *ctx)
 		tbl->poc[i * 2] = dpb[i].top_field_order_cnt;
 		tbl->poc[i * 2 + 1] = dpb[i].bottom_field_order_cnt;
 
+		if (!(dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_VALID))
+			continue;
+
 		/*
 		 * Set up bit maps of valid and long term DPBs.
-		 * NOTE: The bits are reversed, i.e. MSb is DPB 0.
+		 * NOTE: The bits are reversed, i.e. MSb is DPB 0. For frame
+		 * decoding, bit 31 to 15 are used, while for field decoding,
+		 * all bits are used, with bit 31 being a top field, 30 a bottom
+		 * field and so on.
 		 */
-		if (dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_ACTIVE)
-			dpb_valid |= BIT(HANTRO_H264_DPB_SIZE - 1 - i);
-		if (dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM)
-			dpb_longterm |= BIT(HANTRO_H264_DPB_SIZE - 1 - i);
+		if (dec_param->flags & V4L2_H264_DECODE_PARAM_FLAG_FIELD_PIC) {
+			if (dpb[i].fields & V4L2_H264_TOP_FIELD_REF)
+				dpb_valid |= REF_BIT(i * 2);
+
+			if (dpb[i].fields & V4L2_H264_BOTTOM_FIELD_REF)
+				dpb_valid |= REF_BIT(i * 2 + 1);
+
+			if (dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM) {
+				dpb_longterm |= REF_BIT(i * 2);
+				dpb_longterm |= REF_BIT(i * 2 + 1);
+			}
+		} else {
+			dpb_valid |= REF_BIT(i);
+
+			if (dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM)
+				dpb_longterm |= REF_BIT(i);
+		}
+	}
+	ctx->h264_dec.dpb_valid = dpb_valid;
+	ctx->h264_dec.dpb_longterm = dpb_longterm;
+
+	if ((dec_param->flags & V4L2_H264_DECODE_PARAM_FLAG_FIELD_PIC) ||
+	    !(sps->flags & V4L2_H264_SPS_FLAG_MB_ADAPTIVE_FRAME_FIELD)) {
+		tbl->poc[32] = ctx->h264_dec.cur_poc;
+		tbl->poc[33] = 0;
+	} else {
+		tbl->poc[32] = dec_param->top_field_order_cnt;
+		tbl->poc[33] = dec_param->bottom_field_order_cnt;
 	}
-	ctx->h264_dec.dpb_valid = dpb_valid << 16;
-	ctx->h264_dec.dpb_longterm = dpb_longterm << 16;
-
-	tbl->poc[32] = dec_param->top_field_order_cnt;
-	tbl->poc[33] = dec_param->bottom_field_order_cnt;
 
 	assemble_scaling_list(ctx);
 }
@@ -326,6 +358,8 @@ dma_addr_t hantro_h264_get_ref_buf(struct hantro_ctx *ctx,
 {
 	struct v4l2_h264_dpb_entry *dpb = ctx->h264_dec.dpb;
 	dma_addr_t dma_addr = 0;
+	s32 cur_poc = ctx->h264_dec.cur_poc;
+	u32 flags;
 
 	if (dpb[dpb_idx].flags & V4L2_H264_DPB_ENTRY_FLAG_ACTIVE)
 		dma_addr = hantro_get_ref(ctx, dpb[dpb_idx].reference_ts);
@@ -343,7 +377,12 @@ dma_addr_t hantro_h264_get_ref_buf(struct hantro_ctx *ctx,
 		dma_addr = hantro_get_dec_buf_addr(ctx, buf);
 	}
 
-	return dma_addr;
+	flags = dpb[dpb_idx].flags & V4L2_H264_DPB_ENTRY_FLAG_FIELD ? 0x2 : 0;
+	flags |= abs(dpb[dpb_idx].top_field_order_cnt - cur_poc) <
+		 abs(dpb[dpb_idx].bottom_field_order_cnt - cur_poc) ?
+		 0x1 : 0;
+
+	return dma_addr | flags;
 }
 
 u16 hantro_h264_get_ref_nbr(struct hantro_ctx *ctx, unsigned int dpb_idx)
@@ -355,6 +394,47 @@ u16 hantro_h264_get_ref_nbr(struct hantro_ctx *ctx, unsigned int dpb_idx)
 	return dpb->frame_num;
 }
 
+/*
+ * Removes all references with the same parity as the current picture from the
+ * reference list. The remaining list will have references with the opposite
+ * parity. This is effectively a deduplication of references since each buffer
+ * stores two fields. For this reason, each buffer is found twice in the
+ * reference list.
+ *
+ * This technique has been chosen through trial and error. This simple approach
+ * resulted in the highest conformance score. Note that this method may suffer
+ * worse quality in the case an opposite reference frame has been lost. If this
+ * becomes a problem in the future, it should be possible to add a preprocessing
+ * to identify un-paired fields and avoid removing them.
+ */
+static void deduplicate_reflist(struct v4l2_h264_reflist_builder *b,
+				struct v4l2_h264_reference *reflist)
+{
+	int write_idx = 0;
+	int i;
+
+	if (b->cur_pic_fields == V4L2_H264_FRAME_REF) {
+		write_idx = b->num_valid;
+		goto done;
+	}
+
+	for (i = 0; i < b->num_valid; i++) {
+		if (!(b->cur_pic_fields == reflist[i].fields)) {
+			reflist[write_idx++] = reflist[i];
+			continue;
+		}
+	}
+
+done:
+	/* Should not happen unless we have a bug in the reflist builder. */
+	if (WARN_ON(write_idx > 16))
+		write_idx = 16;
+
+	/* Clear the remaining, some streams fails otherwise */
+	for (; write_idx < 16; write_idx++)
+		reflist[write_idx].index = 15;
+}
+
 int hantro_h264_dec_prepare_run(struct hantro_ctx *ctx)
 {
 	struct hantro_h264_dec_hw_ctx *h264_ctx = &ctx->h264_dec;
@@ -386,15 +466,29 @@ int hantro_h264_dec_prepare_run(struct hantro_ctx *ctx)
 	/* Update the DPB with new refs. */
 	update_dpb(ctx);
 
-	/* Prepare data in memory. */
-	prepare_table(ctx);
-
 	/* Build the P/B{0,1} ref lists. */
 	v4l2_h264_init_reflist_builder(&reflist_builder, ctrls->decode,
 				       ctrls->sps, ctx->h264_dec.dpb);
+	h264_ctx->cur_poc = reflist_builder.cur_pic_order_count;
+
+	/* Prepare data in memory. */
+	prepare_table(ctx);
+
 	v4l2_h264_build_p_ref_list(&reflist_builder, h264_ctx->reflists.p);
 	v4l2_h264_build_b_ref_lists(&reflist_builder, h264_ctx->reflists.b0,
 				    h264_ctx->reflists.b1);
+
+	/*
+	 * Reduce ref lists to at most 16 entries, Hantro hardware will deduce
+	 * the actual picture lists in field through the dpb_valid,
+	 * dpb_longterm bitmap along with the current frame parity.
+	 */
+	if (reflist_builder.cur_pic_fields != V4L2_H264_FRAME_REF) {
+		deduplicate_reflist(&reflist_builder, h264_ctx->reflists.p);
+		deduplicate_reflist(&reflist_builder, h264_ctx->reflists.b0);
+		deduplicate_reflist(&reflist_builder, h264_ctx->reflists.b1);
+	}
+
 	return 0;
 }
 

drivers/staging/media/hantro/hantro_hw.h

@@ -83,6 +83,7 @@ struct hantro_h264_dec_reflists {
  * @ctrls:	V4L2 controls attached to a run
  * @dpb_longterm: DPB long-term
  * @dpb_valid:	  DPB valid
+ * @cur_poc:	Current picture order count
  */
 struct hantro_h264_dec_hw_ctx {
 	struct hantro_aux_buf priv;
@@ -91,6 +92,7 @@ struct hantro_h264_dec_hw_ctx {
 	struct hantro_h264_dec_ctrls ctrls;
 	u32 dpb_longterm;
 	u32 dpb_valid;
+	s32 cur_poc;
 };
 
 /**