kcps: fix 0 module CPC case

If a module contains 0 as its CPC value, the consumption calculation
routine will assign a "safe" maximum value to keep the DSP running at
the maximum clock rate. This works when constructing a pipeline, but
when a pipeline is torn down, returning the maximum clock rate leads
to the clock being reduced to a small value. Fix this by detecting
such cases in pipeline termination code.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>

src/audio/pipeline/pipeline-stream.c

@@ -344,11 +344,18 @@ static int pipeline_calc_cps_consumption(struct comp_dev *current,
 
  if (cd->cpc == 0) {
  /* Use maximum clock budget, assume 1ms chunk size */
+ if (!ppl_data->kcps_acc[comp_core])
+ ppl_data->kcps_acc[comp_core] = ppl_data->kcps[comp_core];
  ppl_data->kcps[comp_core] = CLK_MAX_CPU_HZ / 1000;
  tr_warn(pipe,
  "0 CPS requested for module: %#x, core: %d using safe max KCPS: %u",
  current->ipc_config.id, comp_core, ppl_data->kcps[comp_core]);
 
+ /*
+ * This return code indicates to the caller, that the kcps calue
+ * shouldn't be used for slowing down the clock when terminating
+ * the pipeline
+ */
  return PPL_STATUS_PATH_STOP;
  } else {
  kcps = cd->cpc * 1000 / current->period;
@@ -430,6 +437,12 @@ int pipeline_trigger(struct pipeline *p, struct comp_dev *host, int cmd)
  ret = walk_ctx.comp_func(p->source_comp, NULL, &walk_ctx, PPL_DIR_DOWNSTREAM);
 
  for (int i = 0; i < arch_num_cpus(); i++) {
+ if (ret == PPL_STATUS_PATH_STOP) {
+ /* Restore the value before maximization */
+ data.kcps[i] -= data.kcps_acc[i];
+ data.kcps_acc[i] = 0;
+ }
+
  if (data.kcps[i] > 0) {
  core_kcps_adjust(i, -data.kcps[i]);
  tr_info(pipe, "Sum of KCPS consumption: %d, core: %d", core_kcps_get(i), i);

src/include/sof/audio/pipeline.h

@@ -124,6 +124,7 @@ struct pipeline_data {
  uint32_t delay_ms; /* between PRE_{START,RELEASE} and {START,RELEASE} */
 #if CONFIG_KCPS_DYNAMIC_CLOCK_CONTROL
  uint32_t kcps[CONFIG_CORE_COUNT]; /**< the max count of KCPS */
+ uint32_t kcps_acc[CONFIG_CORE_COUNT]; /**< accumulated KCPS before maximization */
 #endif
 };