+static int fsl_asrc_m2m_check_format(u8 dir, u32 rate, u32 channels, u32 format)
+{
+       u64 support_format = FSL_ASRC_FORMATS;
+
+       if (channels < 1 || channels > 10)
+               return -EINVAL;
+
+       if (rate < 5512 || rate > 192000)
+               return -EINVAL;
+

I think we can avoid using magic numbers. Instead we could do:

#define FSL_ASRC_MIN_CHANNELS 1
/...
#define FSL_ASRC_MAX_RATE 192000

+       if (dir == IN)
+               support_format |= SNDRV_PCM_FMTBIT_S8;
+
+       if (!(1 << format & support_format))
+               return -EINVAL;
+
+       return 0;
+}
+
+/* calculate capture data length according to output data length and sample rate */
+static int fsl_asrc_m2m_calc_out_len(struct fsl_asrc_pair *pair, int input_buffer_length)
+{
+       unsigned int in_width, out_width;
+       unsigned int channels = pair->channels;
+       unsigned int in_samples, out_samples;
+       unsigned int out_length;
+
+       in_width = snd_pcm_format_physical_width(pair->sample_format[IN]) / 8;
+       out_width = snd_pcm_format_physical_width(pair->sample_format[OUT]) / 8;
+
+       in_samples = input_buffer_length / in_width / channels;
+       out_samples = pair->rate[OUT] * in_samples / pair->rate[IN];
+       out_length = (out_samples - ASRC_OUTPUT_LAST_SAMPLE) * out_width * channels;
+
+       return out_length;
+}
+
+static int fsl_asrc_m2m_get_maxburst(u8 dir, struct fsl_asrc_pair *pair)
+{
+       struct fsl_asrc *asrc = pair->asrc;
+       struct fsl_asrc_priv *asrc_priv = asrc->private;
+       int wml = (dir == IN) ? ASRC_M2M_INPUTFIFO_WML : ASRC_M2M_OUTPUTFIFO_WML;
+
+       if (!asrc_priv->soc->use_edma)
+               return wml * pair->channels;
+       else
+               return 1;
+}
+
+static int fsl_asrc_m2m_pair_resume(struct fsl_asrc_pair *pair)
+{
+       struct fsl_asrc *asrc = pair->asrc;
+       int i;
+
+       for (i = 0; i < pair->channels * 4; i++)
+               regmap_write(asrc->regmap, REG_ASRDI(pair->index), 0);
+
+       return 0;
+}
+
 static int fsl_asrc_runtime_resume(struct device *dev);
 static int fsl_asrc_runtime_suspend(struct device *dev);

<snip>

There is no implementation for _suspend although you mention it
in the commit message.

+ * @complete: dma task complete
+ * @sample_format: format of m2m
+ * @rate: rate of m2m
+ * @buf_len: buffer length of m2m
+ * @req_pair: flag for request pair

For example @complete field is not used in this patch. Maybe add it in the patch
that uses it?

I think is the same for other fields.