Re: [PATCH] soundwire: qcom: wait for fifo space to be available before read/write

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+static int swrm_wait_for_rd_fifo_avail(struct qcom_swrm_ctrl *swrm)
+{
+	u32 fifo_outstanding_cmd, value;
+	u8 fifo_retry_count = SWR_OVERFLOW_RETRY_COUNT;
+
+	/* Check for fifo underflow during read */
+	swrm->reg_read(swrm, SWRM_CMD_FIFO_STATUS, &value);
+	fifo_outstanding_cmd = FIELD_GET(SWRM_RD_CMD_FIFO_CNT_MASK, value);
+
+	 /* Check number of outstanding commands in fifo before read */
+	if (fifo_outstanding_cmd)
+		return 0;
+
+	do {
+		usleep_range(500, 510);
+		swrm->reg_read(swrm, SWRM_CMD_FIFO_STATUS, &value);
+		fifo_outstanding_cmd = FIELD_GET(SWRM_RD_CMD_FIFO_CNT_MASK, value);
+		if (fifo_outstanding_cmd > 0)
+			break;
+	} while (fifo_retry_count--);
+
+	if (fifo_outstanding_cmd == 0) {
+		dev_err_ratelimited(swrm->dev, "%s err read underflow\n", __func__);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+static int swrm_wait_for_wr_fifo_avail(struct qcom_swrm_ctrl *swrm)
+{
+	u32 fifo_outstanding_cmd, value;
+	u8 fifo_retry_count = SWR_OVERFLOW_RETRY_COUNT;
+
+	/* Check for fifo overflow during write */
+	swrm->reg_read(swrm, SWRM_CMD_FIFO_STATUS, &value);
+	fifo_outstanding_cmd = FIELD_GET(SWRM_WR_CMD_FIFO_CNT_MASK, value);
+
+	/* Check number of outstanding commands in fifo before write */
+	if (fifo_outstanding_cmd != swrm->wr_fifo_depth)
+		return 0;
+
+	do {
+		usleep_range(500, 510);
+		swrm->reg_read(swrm, SWRM_CMD_FIFO_STATUS, &value);
+		fifo_outstanding_cmd = FIELD_GET(SWRM_WR_CMD_FIFO_CNT_MASK, value);
+		if (fifo_outstanding_cmd < swrm->wr_fifo_depth)
+			break;
+	} while (fifo_retry_count--);
+
+	if (fifo_outstanding_cmd == swrm->wr_fifo_depth) {
+		dev_err_ratelimited(swrm->dev, "%s err write overflow\n", __func__);
+		return -ENOMEM;
+	}
+
+	return 0;
+}

nit-pick: you could merge the prologue and loop body with a while(fifo_retry_count--) and put the usleep_range() at the end of the loop.




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