[igt-dev] [PATCH i-g-t v5] tools: Add an intel_dbuf_map tool

Juha-Pekka Heikkilä juha-pekka.heikkila at intel.com
Mon Dec 30 14:18:21 UTC 2019


just some small comments below on the code. I'll need to run the tool 
somewhere to give more meaningful comments.

/Juha-Pekka

On 30.12.2019 11.07, Stanislav Lisovskiy wrote:
> As in modern platforms more Display buffer
> slices/pipes are coming, which have different
> pipe affinities and other constraints, so BSpec
> contains their connection in form of a Graph.
> 
> So we can generate optimal DBuf assignment,
> from the graph which we have in BSpec, to avoid
> manual calculations prone to human error and
> copy-pasting. The generated table is in C form
> and can be used in i915 driver rightaway and also
> for verification.
> 
> v2: Removed unused i, j, made some functions static,
>      to make CI checkers a bit happier. Also had to
>      change IGT_LIST to IGT_LIST_HEAD and other stuff,
>      as functions seem to be renamed in latest master.
> 
> v3: Added command line arguments "--graph" and
>      "slices_per_pipe" which allow to define and
>      get DBuf assignment from graph without recompiling
>      the tool, but right away.
>      Example usage:
>      intel_dbuf_map --graph PIPE_A-DBUF_S1-DBUF_S2-PIPE_B-PIPE_C --slices_per_pipe 2
> 
>      Generates output:
>      Graph:
>      Type PIPE id 0
>          (1)->
>               Type DBUF_SLICE id 0
>                  (1)->
>                      Type DBUF_SLICE id 1
>                          (1)->
>                              Type PIPE id 1
>                                  (1)->
>                                      Type PIPE id 2
>      Combination with least weight 3(total combinations 1):
>      { BIT(PIPE_A), { DBUF_S1_BIT | DBUF_S2_BIT, 0, 0, 0 } },
>      Combination with least weight 3(total combinations 1):
>      { BIT(PIPE_B), { 0, DBUF_S2_BIT | DBUF_S1_BIT, 0, 0 } },
>      Combination with least weight 2(total combinations 2):
>      { BIT(PIPE_A) | BIT(PIPE_B), { DBUF_S1_BIT, DBUF_S2_BIT, 0, 0 } },
>      Combination with least weight 5(total combinations 1):
>      { BIT(PIPE_C), { 0, 0, DBUF_S2_BIT | DBUF_S1_BIT, 0 } },
>      Combination with least weight 3(total combinations 2):
>      { BIT(PIPE_A) | BIT(PIPE_C), { DBUF_S1_BIT, 0, DBUF_S2_BIT, 0 } },
>      Combination with least weight 4(total combinations 2):
>      { BIT(PIPE_B) | BIT(PIPE_C), { 0, DBUF_S2_BIT, DBUF_S1_BIT, 0 } },
>      Combination with least weight 4(total combinations 6):
>      { BIT(PIPE_A) | BIT(PIPE_B) | BIT(PIPE_C), { DBUF_S1_BIT, DBUF_S2_BIT, DBUF_S2_BIT, 0 } },
> 
> v4: - Minor refactoring, simplified algorithm, removed redundant list
>        usage
>      - Fixed title
>      - Added debug option
>      - Removed unneeded ARRAY_SIZE definition, which already exists
>        (Juha-Pekka Heikkilä)
> 
> v5: - Switched to named pipe array initialization, to match current
>        kernel code.
>      - Minor code refactoring.
> 
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>   tools/intel_dbuf_map.c | 884 +++++++++++++++++++++++++++++++++++++++++
>   tools/meson.build      |   1 +
>   2 files changed, 885 insertions(+)
>   create mode 100644 tools/intel_dbuf_map.c
> 
> diff --git a/tools/intel_dbuf_map.c b/tools/intel_dbuf_map.c
> new file mode 100644
> index 00000000..ac42f608
> --- /dev/null
> +++ b/tools/intel_dbuf_map.c
> @@ -0,0 +1,884 @@
> +/*
> + * Copyright © 2019 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> + * DEALINGS IN THE SOFTWARE.
> + *
> + * Authors:
> + *    Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> + *
> + */
> +
> +#include <stdlib.h>
> +#include "igt.h"
> +
> +enum NodeType {
> +	DBUF_SLICE,
> +	PIPE
> +};
> +
> +const char *node_type_to_str[] = { "DBUF_SLICE", "PIPE" };
> +
> +#define MAX_CONNECTIONS 10
> +#define MAX_NODES 10
> +#define MAX_EDGES (MAX_NODES * 2)
> +
> +struct GraphEdge;
> +
> +/*
> + * Graph node, which can be DBuf or Pipe
> + */
> +struct GraphNode {
> +	int id;
> +	enum NodeType type;
> +	unsigned int use_count;
> +	int visited;
> +	struct GraphEdge *connections[MAX_CONNECTIONS];
> +	int num_connections;
> +};
> +
> +static struct GraphNode *all_nodes[MAX_NODES];
> +static struct GraphEdge *all_edges[MAX_EDGES];
> +static int num_nodes;
> +static int num_edges;
> +
> +/*
> + * Graph edge, which connects Graph nodes
> + * and has a weight property.
> + */
> +struct GraphEdge {
> +	unsigned int weight;
> +	struct GraphNode *node;
> +};

If you move GraphEdge structure bit upward you can take out forward 
declaration for this structure above GraphNode.

> +
> +static struct GraphNode *create_graph_node(enum NodeType type, int id)
> +{
> +	struct GraphNode *node = 0;
> +
> +	if (num_nodes >= MAX_NODES) {
> +		igt_info("Too much nodes %d", num_nodes);
> +		return NULL;
> +	}
> +
> +	node = malloc(sizeof(struct GraphNode));
> +	node->type = type;
> +	node->id = id;
> +	node->use_count = 0;
> +	node->visited = 0;
> +	memset(node->connections, 0,
> +			MAX_CONNECTIONS * sizeof(struct GraphEdge *));

You could allocate with calloc instead of malloc + memset + zeroing 
individual members.

> +	node->num_connections = 0;
> +
> +	all_nodes[num_nodes] = node;
> +	num_nodes++;
> +
> +	return node;
> +}
> +
> +static struct GraphEdge *create_graph_edge(int weight, struct GraphNode *node)
> +{
> +	struct GraphEdge *edge = 0;
> +
> +	if (num_edges >= MAX_EDGES) {
> +		igt_info("Too much edges %d", num_edges);
> +		return NULL;
> +	}
> +
> +	edge = malloc(sizeof(struct GraphEdge));
> +
> +	edge->node = node;
> +	edge->weight = weight;
> +
> +	all_edges[num_edges] = edge;
> +	num_edges++;
> +
> +	return edge;
> +}
> +
> +static void connect_nodes(struct GraphNode *node1, struct GraphNode *node2, int weight)
> +{
> +	struct GraphEdge *edge1;
> +	struct GraphEdge *edge2;
> +
> +	if (node1->num_connections >= MAX_CONNECTIONS) {
> +		igt_info("Node %d has too much connections\n", node1->id);
> +		return;
> +	}
> +
> +	if (node2->num_connections >= MAX_CONNECTIONS) {
> +		igt_info("Node %d has too much connections\n", node2->id);
> +		return;
> +	}
> +
> +	edge1 = create_graph_edge(weight, node1);
> +	edge2 = create_graph_edge(weight, node2);
> +
> +	node1->connections[node1->num_connections] = edge2;
> +	node1->num_connections++;
> +	node2->connections[node2->num_connections] = edge1;
> +	node2->num_connections++;
> +}
> +
> +static void reset_node(struct GraphNode *node)
> +{
> +	node->use_count = 0;
> +	node->visited = 0;
> +	memset(node->connections, 0,
> +		MAX_CONNECTIONS * sizeof(struct GraphEdge *));
> +	node->num_connections = 0;
> +}
> +
> +static void destroy_node(struct GraphNode *node)
> +{
> +	free(node);
> +}
> +
> +static void destroy_edge(struct GraphEdge *edge)
> +{
> +	free(edge);
> +}
> +
> +static void destroy_all_edges(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < num_edges; i++) {
> +		destroy_edge(all_edges[i]);
> +	}
> +	num_edges = 0;
> +}
> +
> +static void destroy_all_nodes(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < num_nodes; i++) {
> +		destroy_node(all_nodes[i]);
> +	}
> +	num_nodes = 0;
> +}
> +
> +static void reset_all_nodes(void)
> +{
> +	int i;
> +
> +	destroy_all_edges();
> +
> +	for (i = 0; i < num_nodes; i++) {
> +		reset_node(all_nodes[i]);
> +	}
> +}
> +
> +/*
> + * Traverse and try to print graph in a
> + * somewhat graphical form.
> + */
> +static void traverse_graph(struct GraphNode *start_node,
> +			   int depth)
> +{
> +	int i, space;
> +
> +	if (!depth)
> +		igt_info("Graph: \n");
> +
> +	for (space = 0; space < depth * 4; space++)
> +		igt_info(" ");
> +
> +	start_node->visited++;
> +	igt_info("Type %s id %d\n", node_type_to_str[start_node->type],
> +		 start_node->id);
> +	for (i = 0; i < start_node->num_connections; i++) {
> +		if (!start_node->connections[i]->node->visited) {
> +			for (space = 0; space < (depth + 1) * 4; space++)
> +				igt_info(" ");
> +			igt_info("(%d)-> \n", start_node->connections[i]->weight);
> +			traverse_graph(start_node->connections[i]->node, depth+2);
> +			start_node->connections[i]->node->visited--;
> +		}
> +	}
> +}
> +
> +bool debug = false;
> +
> +static void print_node_debug(struct GraphNode *node)
> +{
> +	igt_info("%s node %d visited %d use count %d\n",
> +		 node_type_to_str[node->type], node->id,
> +		 node->visited,
> +		 node->use_count);
> +}
> +
> +/*
> + * This function recursively searches for a free DBuf slice
> + * for correspondent pipe, based on different constraints, like
> + * weight, usage count. This algorithm is "greedy" which means
> + * that it accounts for local optimum only, which means that
> + * total comparison has to be done in the end.
> + * In graph theory this is called breadth-first search.
> + * As this algorithm tries to utilize nearest neighbours first
> + * it allows to skip many unrequired path calculations which
> + * would be needed if we really would build a matrix like:
> + *   Pipe - DBUF
> + *         0    1
> + *   0     1    2
> + *
> + *   1     2    1
> + * Then we would have to go thourgh all N Dbuf * N Pipes * N Pipes!
> + * to check all possible pipe accomodations.
> + * For above matrix the algorithm would immediately return slice 0
> + * for pipe 0 and slice 1 for pipe 1 as nearest neighbours, skipping
> + * unneccessary paths for pipe0 - slice1, pipe1 - slice0.
> + * Anyway for more complex cases, like:
> + *  Pipe - DBUF
> + *         0    1
> + *   0     1    1
> + *
> + *   1     2    1
> + * checking for all possible accomodations is still needed. However
> + * nearest "greedy" approach first still allows to filter out some of
> + * the redundant combinations, which would be seen if full matrix is built.
> + * Instead we save time by just choosing the nearest ones first which
> + * are expected to have lower cost(greedy approach), however then
> + * we will still check all possible accomodations as we would do with
> + * full matrix approach.
> + */
> +static struct GraphNode *find_slice_for_pipe(struct GraphNode *start_node,
> +					     int acc_weight, int max_use_count,
> +					     unsigned int *total_weight,
> +					     int depth,
> +					     int *skip)
> +{
> +	int i;
> +	struct GraphNode *node = NULL;
> +
> +	if (debug) {
> +		igt_info("Entering node(resursion depth %d skips %d): \n",
> +			 depth, *skip);
> +		print_node_debug(start_node);
> +		igt_info("Accumulated weight %d max use count %d\n",
> +			 acc_weight, max_use_count);
> +	}
> +
> +	start_node->visited++;
> +
> +	/*
> +	 * Iterate through neighbouring slices(graph breadth-first search),
> +	 * checking if it's use count allows usage and skip if needed,
> +	 * skips are needed when we use multiple slices for
> +	 * same pipe to prevent algorithm from returning the
> +	 * same DBuf.
> +	 */
> +	for (i = 0; i < start_node->num_connections; i++) {
> +		struct GraphEdge *cur_edge = start_node->connections[i];
> +
> +		if (debug) {
> +			igt_info("    Neighbour node: ");
> +			print_node_debug(cur_edge->node);
> +		}
> +
> +		if (cur_edge->node->type != DBUF_SLICE)
> +			continue;
> +
> +		if (cur_edge->node->use_count < max_use_count) {
> +			if (!(*skip)) {
> +				cur_edge->node->use_count++;
> +				*total_weight = acc_weight + cur_edge->weight;
> +				node = cur_edge->node;
> +				goto out;
> +			}
> +		}
> +
> +		if (*skip)
> +			(*skip)--;
> +	}
> +
> +	/*
> +	 * If couldn't find suitable DBuf node from our
> +	 * neighbours, have to continue further, checking
> +	 * visited flag, to prevent loops.
> +	 */
> +	for (i = 0; i < start_node->num_connections; i++) {
> +		struct GraphEdge *cur_edge = start_node->connections[i];
> +
> +		if (cur_edge->node->visited)
> +			continue;
> +
> +		node = find_slice_for_pipe(cur_edge->node,
> +					   acc_weight + cur_edge->weight,
> +					   max_use_count, total_weight,
> +					   depth + 1, skip);
> +		cur_edge->node->visited--;
> +		if (node)
> +			goto out;
> +	}
> +
> +out:
> +	if (debug)
> +		igt_info("Leaving node %d\n", start_node->id);
> +
> +	/* If we are at recursion depth 0 - release the root node */
> +	if (depth == 0)
> +		start_node->visited = 0;
> +
> +	return node;
> +}
> +
> +static int hweight32(int mask)
> +{
> +	int i;
> +	int count = 0;
> +
> +	for (i = 0; i < 32; i++)
> +		if ((1<<i) & mask)
> +			count += 1;
> +	return count;
> +}
> +
> +#define I915_MAX_PIPES 4
> +#define I915_MAX_SLICES_PER_PIPE 4
> +#define I915_MAX_SLICES (I915_MAX_PIPES * I915_MAX_SLICES_PER_PIPE)
> +
> +const char *pipe_names[] = { "PIPE_A", "PIPE_B", "PIPE_C", "PIPE_D" };
> +const char *slice_names[] = { "DBUF_S1", "DBUF_S2", "DBUF_S3", "DBUF_S4" };
> +
> +static int factorial(int n)
> +{
> +	if (n <= 1)
> +		return 1;
> +	return n * factorial(n - 1);
> +}
> +
> +static void do_swap(struct GraphNode **pipe_nodes, int m, int n)
> +{
> +	struct GraphNode *node1 = pipe_nodes[m];
> +	struct GraphNode *node2 = pipe_nodes[n];
> +	unsigned long node_val1 = (unsigned long) node1;
> +	unsigned long node_val2 = (unsigned long) node2;
> +
> +	node_val1 ^= node_val2;
> +	node_val2 ^= node_val1;
> +	node_val1 ^= node_val2;
> +
> +	node1 = (struct GraphNode *)node_val1;
> +	node2 = (struct GraphNode *)node_val2;
> +}
> +
> +struct PipeNodesCombination {
> +	unsigned int total_weight;
> +	struct GraphNode *pipe_nodes[I915_MAX_PIPES];
> +	struct GraphNode *slices[I915_MAX_SLICES];
> +};
> +
> +struct IterateContext {
> +	struct PipeNodesCombination min_comb;
> +	int max_use_count;
> +	int num_pipes;
> +	int num_slices;
> +	int slices_per_pipe;
> +	int max_combinations;
> +};
> +
> +struct PipeDBuf {
> +	struct GraphNode *pipe;
> +	struct GraphNode *dbuf[I915_MAX_SLICES_PER_PIPE];
> +};
> +
> +static void print_pipe_nodes(struct GraphNode **pipe_nodes)
> +{
> +	int i;
> +	for (i = 0; i < I915_MAX_PIPES; i++) {
> +		if (!pipe_nodes[i])
> +			igt_info("(null)");
> +		else
> +			igt_info("%d", pipe_nodes[i]->id);
> +		if ( i < (I915_MAX_PIPES - 1))
> +			igt_info(" ,");
> +	}
> +	igt_info("\n");
> +}
> +
> +
> +static void compare_weight(struct IterateContext *ctx,
> +			   struct PipeNodesCombination *comb)
> +{
> +	unsigned int weight;
> +	int j = 0;
> +	int pipe = 0;
> +	int skip = 0;
> +	int slice_num = 0;
> +
> +	comb->total_weight = 0;
> +
> +	if (debug) {
> +		igt_info("Combination: ");
> +		print_pipe_nodes(comb->pipe_nodes);
> +	}
> +
> +	/*
> +	 * Get a free DBuf slice for each pipe, then
> +	 * calculate total weight, which will be
> +	 * then compared to minimal weight to find
> +	 * combination with total minimal weight.
> +	 */
> +	while (pipe < I915_MAX_PIPES) {
> +		if (comb->pipe_nodes[pipe]) {
> +			slice_num = 0;
> +			skip = 0;
> +			while (slice_num < ctx->slices_per_pipe) {
> +				skip = slice_num;
> +				comb->slices[j] =
> +				    find_slice_for_pipe(comb->pipe_nodes[pipe],
> +						0, ctx->max_use_count,
> +						&weight, 0, &skip);
> +				if (!comb->slices[j])
> +					break;
> +				slice_num++;
> +				j++;
> +				comb->total_weight += weight;
> +			}
> +		} else {
> +			j += ctx->slices_per_pipe;
> +		}
> +		pipe++;
> +	}
> +
> +	if (debug)
> +		igt_info("Total weight %d\n", comb->total_weight);
> +
> +	for (j = 0; j < I915_MAX_SLICES; j++) {
> +		if (comb->slices[j])
> +			comb->slices[j]->use_count = 0;
> +	}
> +
> +	if (ctx->min_comb.total_weight > comb->total_weight) {
> +		memcpy(&ctx->min_comb, comb,
> +		       sizeof(struct PipeNodesCombination));
> +	}
> +}
> +
> +/*
> + * Generate all possible combinations for elements in
> + * pipe array(total is calculated as n!).
> + */
> +static void iterate_all_combinations(struct IterateContext *ctx,
> +				     struct GraphNode **pipe_nodes,
> +				     int start, int step,
> +				     void (*func)(struct IterateContext *ctx,
> +				     struct PipeNodesCombination *comb))
> +{
> +	int i, j;
> +	struct GraphNode *nodes[I915_MAX_PIPES];
> +	struct PipeNodesCombination comb;
> +
> +	memcpy(comb.pipe_nodes, pipe_nodes,
> +	       I915_MAX_PIPES * sizeof(struct GraphNode *));
> +	memset(comb.slices, 0,
> +	       I915_MAX_SLICES * sizeof(struct GraphNode *));
> +
> +	if (func)
> +		(*func)(ctx, &comb);
> +
> +	if ((step == 0) || (ctx->num_pipes == 1))
> +		return;
> +
> +	for (j = step; j > 0; j--) {
> +		for (i = start; i < I915_MAX_PIPES - j; i++) {
> +			if (!pipe_nodes[i] || !pipe_nodes[i + j])
> +				continue;
> +			memcpy(nodes, pipe_nodes,
> +			       I915_MAX_PIPES * sizeof(struct GraphNode *));
> +			do_swap(nodes, i, i + j);
> +			iterate_all_combinations(ctx, nodes, i + 1,
> +						 step - 1, func);
> +		}
> +	}
> +}
> +
> +/*
> + * This function calculates and prints optimal
> + * weight-based DBuf assignment for active pipes.
> + */
> +static int
> +print_dbuf_mask_for_pipes(int active_pipes,
> +			  struct GraphNode **pipe_nodes,
> +			  int num_slices)
> +{
> +	int i;
> +	int num_pipes = hweight32(active_pipes), pipes_count;
> +	int max_use_count = num_slices < num_pipes ? 2 : 1;
> +	int pipe = 0;
> +	int slices_per_pipe = max(num_slices / num_pipes, 1);
> +	struct IterateContext ctx;
> +	struct PipeDBuf pipe_dbuf[I915_MAX_PIPES];
> +
> +	memcpy(ctx.min_comb.pipe_nodes, pipe_nodes,
> +	       sizeof(struct GraphNode *) * I915_MAX_PIPES);
> +	memset(ctx.min_comb.slices, 0,
> +	       I915_MAX_SLICES * sizeof(struct GraphNode *));
> +	ctx.min_comb.total_weight = ~0;
> +	ctx.max_use_count = max_use_count;
> +	ctx.num_pipes = num_pipes;
> +	ctx.num_slices = num_slices;
> +	ctx.slices_per_pipe = slices_per_pipe;
> +	ctx.max_combinations = factorial(num_pipes);
> +
> +	iterate_all_combinations(&ctx, pipe_nodes,
> +				 0, I915_MAX_PIPES - 1, compare_weight);
> +
> +	if (debug)
> +		igt_info("Combination with least weight %d(total combinations %d):\n",
> +		         ctx.min_comb.total_weight, ctx.max_combinations);
> +
> +	memset(pipe_dbuf, 0, sizeof(struct PipeDBuf) * I915_MAX_PIPES);
> +
> +	for (i = 0; i < I915_MAX_PIPES; i++) {
> +		if (ctx.min_comb.pipe_nodes[i]) {
> +			int pipe_index = ctx.min_comb.pipe_nodes[i]->id;
> +
> +			pipe_dbuf[pipe_index].pipe = ctx.min_comb.pipe_nodes[i];
> +			memcpy(&pipe_dbuf[pipe_index].dbuf,
> +			       &ctx.min_comb.slices[i * slices_per_pipe],
> +			       sizeof(struct GraphNode *) * slices_per_pipe);
> +		}
> +	}
> +
> +	igt_info("\t\t{\n");
> +	pipe = 0;
> +	igt_info("\t\t\t\t.active_pipes = ");
> +	for (i = 0; i < I915_MAX_PIPES; i++) {
> +		if (pipe_dbuf[i].pipe) {
> +			igt_info("BIT(%s)", pipe_names[pipe_dbuf[i].pipe->id]);
> +			if (pipe < (num_pipes - 1))
> +				igt_info(" | ");
> +			pipe++;
> +		}
> +	}
> +	igt_info(",\n\t\t\t\t{\n");
> +	num_pipes = 0;
> +	for (pipe = 0; pipe < I915_MAX_PIPES; pipe++)
> +		if (pipe_dbuf[pipe].pipe)
> +			num_pipes++;
> +
> +	pipes_count = 0;
> +	for (pipe = 0; pipe < I915_MAX_PIPES; pipe++) {
> +		if (pipe_dbuf[pipe].pipe) {
> +			igt_info("\t\t\t\t\t\t[%s] = ", pipe_names[pipe_dbuf[pipe].pipe->id]);
> +			for (i = 0; i < slices_per_pipe; i++) {
> +				int slice_index_converted;
> +				struct GraphNode *next_slice =
> +						pipe_dbuf[pipe].dbuf[i+1];
> +				bool not_last = i < (slices_per_pipe - 1);
> +
> +				if (!pipe_dbuf[pipe].dbuf[i])
> +					break;
> +
> +				slice_index_converted =
> +					pipe_dbuf[pipe].dbuf[i]->id;
> +
> +				if (not_last && next_slice) {
> +					igt_info("BIT(DBUF_S%d) | ",
> +						 slice_index_converted + 1);
> +				} else {
> +					igt_info("BIT(DBUF_S%d)",
> +						 slice_index_converted + 1);
> +				}
> +				pipes_count++;
> +			}
> +			if (pipes_count < num_pipes) {
> +					igt_info(",\n");
> +			}
> +			else
> +				break;
> +		}
> +	}
> +	igt_info("\n\t\t\t\t}\n\t\t},\n");
> +
> +	return 0;
> +}
> +
> +static void print_table(struct GraphNode **pipes, int num_pipes,
> +			struct GraphNode **slices, int num_slices,
> +			int slices_per_pipe)
> +{
> +	unsigned int i, j;
> +	int num_combinations = 1 << num_pipes;
> +
> +	if (num_pipes > I915_MAX_PIPES) {
> +		igt_info("Too many pipes %d\n", num_pipes);
> +		return;
> +	}
> +
> +	if (num_slices > I915_MAX_SLICES) {
> +		igt_info("Too many slices %d\n", num_slices);
> +		return;
> +	}
> +
> +	igt_info("/* Autogenerated with igt/tools/intel_dbuf_map tool: */\n");
> +	igt_info("{\n");
> +	for (i = 1; i < num_combinations; i++) {
> +		struct GraphNode *tmp[I915_MAX_PIPES];
> +
> +		memcpy(tmp, pipes, I915_MAX_PIPES * sizeof(struct GraphNode *));
> +
> +		for (j = 0; j < I915_MAX_SLICES; j++) {
> +			if (slices[j])
> +				slices[j]->use_count = 0;
> +		}
> +
> +		for (j = 0; j < I915_MAX_PIPES; j++) {
> +			if (!(i & (1 << j))) {
> +				tmp[j] = 0;
> +			}
> +		}
> +
> +		if (print_dbuf_mask_for_pipes(i, tmp, num_slices))
> +			break;
> +	}
> +	igt_info("};\n");
> +}
> +
> +enum opt {
> +	OPT_UNKNOWN = '?',
> +	OPT_END = -1,
> +	OPT_GEN,
> +	OPT_USAGE,
> +	OPT_GRAPH,
> +	OPT_DEBUG,
> +	OPT_SLICES_PER_PIPE
> +};
> +
> +static void usage(const char *toolname)
> +{
> +	fprintf(stderr, "usage: %s", toolname);
> +	fprintf(stderr, " [--gen=<GEN>]"
> +			" [--slices_per_pipe=<number>]"
> +			" [--graph=\"PIPE_A-DBUF_S1-PIPE_B-...\"]"
> +			" [--debug]"
> +			" [--help]\n");
> +}
> +
> +static int pipe_str_to_num(const char *str)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(pipe_names); i++) {
> +		if (!strcmp(str, pipe_names[i])) {
> +			return i;
> +		}
> +	}
> +	return -1;
> +}
> +
> +static int dbuf_str_to_num(const char *str)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(slice_names); i++) {
> +		if (!strcmp(str, slice_names[i])) {
> +			return i;
> +		}
> +	}
> +	return -1;
> +}
> +
> +#define MAX_GRAPH_STR 80
> +
> +static void parse_graph_str(char *graph_str, struct GraphNode **pipes,
> +			    struct GraphNode **slices, int *num_slices,
> +			    int *num_pipes)
> +{
> +	char* token = strtok(graph_str, "-");
> +	struct GraphNode *cur_node = NULL, *last_node = NULL;
> +	int n_pipes = 0, n_slices = 0;
> +
> +	while (token != NULL) {
> +		int index;
> +
> +		index = pipe_str_to_num(token);
> +
> +		last_node = cur_node;
> +		if (index >= 0) {
> +			cur_node = pipes[index];
> +			n_pipes++;
> +		} else {
> +			index = dbuf_str_to_num(token);
> +			if (index >= 0) {
> +				cur_node = slices[index];
> +				n_slices++;
> +			}
> +		}
> +		if (last_node && cur_node)
> +			connect_nodes(last_node, cur_node, 1);
> +
> +		token = strtok(NULL, "-");
> +	}
> +	*num_slices = n_slices;
> +	*num_pipes = n_pipes;
> +}
> +
> +int main(int argc, char **argv)
> +{
> +	struct GraphNode *pipes[I915_MAX_PIPES];
> +	struct GraphNode *slices[I915_MAX_SLICES];
> +	struct GraphNode *pipeA, *pipeB, *pipeC, *pipeD;
> +	struct GraphNode *slice1, *slice2, *slice3, *slice4;
> +	int gen = 12, index;
> +	enum opt opt;
> +	char *endp;
> +	char graph_str[MAX_GRAPH_STR];
> +	int slices_per_pipe = I915_MAX_SLICES_PER_PIPE;
> +	const char *toolname = argv[0];
> +	static struct option options[] = {
> +		{ "gen",		required_argument,	NULL,	OPT_GEN },
> +		{ "graph",		required_argument,	NULL,	OPT_GRAPH },
> +		{ "slices_per_pipe",	required_argument,	NULL,	OPT_SLICES_PER_PIPE },
> +		{ "help",		no_argument,		NULL,	OPT_USAGE },
> +		{ "debug",		no_argument,		NULL,	OPT_DEBUG },
> +		{ 0 }
> +	};
> +
> +	num_edges = 0;
> +	num_nodes = 0;
> +
> +	for (opt = 0; opt != OPT_END; ) {
> +		opt = getopt_long(argc, argv, "", options, &index);
> +
> +		switch (opt) {
> +		case OPT_GEN:
> +			gen = strtoul(optarg, &endp, 0);
> +			break;
> +		case OPT_SLICES_PER_PIPE:
> +			slices_per_pipe = min(strtoul(optarg, &endp, 0),
> +					      I915_MAX_SLICES_PER_PIPE);
> +			break;
> +		case OPT_DEBUG:
> +			debug = true;
> +			break;
> +		case OPT_GRAPH:
> +			strncpy(graph_str, optarg, MAX_GRAPH_STR);
> +			graph_str[MAX_GRAPH_STR - 1] = 0;
> +			gen = 0;
> +		case OPT_END:
> +			break;
> +		case OPT_USAGE: /* fall-through */
> +		case OPT_UNKNOWN:
> +			usage(toolname);
> +			return EXIT_FAILURE;
> +		}
> +	}
> +	pipeA = create_graph_node(PIPE, 0);
> +	pipeB = create_graph_node(PIPE, 1);
> +	pipeC = create_graph_node(PIPE, 2);
> +	pipeD = create_graph_node(PIPE, 3);
> +	slice1 = create_graph_node(DBUF_SLICE, 0);
> +	slice2 = create_graph_node(DBUF_SLICE, 1);
> +	slice3 = create_graph_node(DBUF_SLICE, 2);
> +	slice4 = create_graph_node(DBUF_SLICE, 3);
> +
> +	memset(pipes, 0, I915_MAX_PIPES * sizeof(struct GraphNode *));
> +	memset(slices, 0, I915_MAX_SLICES * sizeof(struct GraphNode *));
> +
> +	if (!gen) {
> +		int num_slices = 0, num_pipes = 0;
> +		/*
> +		 * Prepare to generate assignments for ICL, which
> +		 * has 3 pipes and 2 DBuf slices.
> +		 */

cut'n'paste comment above? :)

> +		slices[0] = slice1;
> +		slices[1] = slice2;
> +		slices[2] = slice3;
> +		slices[3] = slice4;
> +		pipes[0] = pipeA;
> +		pipes[1] = pipeB;
> +		pipes[2] = pipeC;
> +		pipes[3] = pipeD;
> +
> +		parse_graph_str(graph_str, pipes, slices, &num_slices,
> +				&num_pipes);
> +
> +		traverse_graph(pipes[0], 0);
> +
> +		print_table(pipes, num_pipes, slices, num_slices, slices_per_pipe);
> +
> +	} else if (gen == 11) {
> +
> +		/*
> +		 * Prepare to generate assignments for ICL, which
> +		 * has 3 pipes and 2 DBuf slices.
> +		 */
> +		slices[0] = slice1;
> +		slices[1] = slice2;
> +		pipes[0] = pipeA;
> +		pipes[1] = pipeB;
> +		pipes[2] = pipeC;
> +
> +		/*
> +		 * BSpec 12716. Generate DBuf Slices table for ICL,
> +		 * Graph(each edge assumed to have weight 1):
> +		 * PipeA - DBUF_S1 - PipeB - PipeC - DBUF_S2
> +		 */
> +		connect_nodes(pipeA, slice1, 1);
> +		connect_nodes(slice1, pipeB, 1);
> +		connect_nodes(pipeB, pipeC, 1);
> +		connect_nodes(pipeC, slice2, 1);
> +
> +		traverse_graph(pipeA, 0);
> +
> +		print_table(pipes, 3, slices, 2, 2);
> +
> +	} else if (gen == 12) {
> +
> +		/*
> +		 * Prepare to generate assignments for TGL, which
> +		 * has 4 pipes and 2 DBuf slices.
> +		 */
> +		slices[0] = slice1;
> +		slices[1] = slice2;
> +		pipes[0] = pipeA;
> +		pipes[1] = pipeB;
> +		pipes[2] = pipeC;
> +		pipes[3] = pipeD;
> +
> +		/*
> +		 * BSpec 49255. Generate DBuf Slices table for TGL.
> +		 * Graph(each edge assumed to have weight 1):
> +		 * PipeD - DBUF_S2 - PipeC - PipeA - DBUF_S1 - PipeB
> +		 */
> +		connect_nodes(pipeD, slice2, 1);
> +		connect_nodes(slice2, pipeC, 1);
> +		connect_nodes(pipeC, pipeA, 1);
> +		connect_nodes(pipeA, slice1, 1);
> +		connect_nodes(slice1, pipeB, 1);
> +
> +		traverse_graph(pipeA, 0);
> +
> +		print_table(pipes, 4, slices, 2, 2);
> +	}

What about if gen == 13? Maybe add some form of comment if none of the 
paths was chosen. Convert to switch {case:; default:;} where default 
would list why no path was chosen?

> +
> +	reset_all_nodes();
> +
> +	/*
> +	 * Further platforms can generate table same way.
> +	 */
> +
> +	destroy_all_nodes();
> +
> +	return  0;
> +}
> +
> diff --git a/tools/meson.build b/tools/meson.build
> index eecb122b..2b8df4b4 100644
> --- a/tools/meson.build
> +++ b/tools/meson.build
> @@ -35,6 +35,7 @@ tools_progs = [
>   	'intel_watermark',
>   	'intel_gem_info',
>   	'intel_gvtg_test',
> +	'intel_dbuf_map',
>   	'dpcd_reg',
>   ]
>   tool_deps = igt_deps
> 
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