On Wed, Apr 10, 2019 at 03:15:26AM +0000, S.j. Wang wrote:
The table is not flexible if supported sample rate is not in the table, so use a function to replace it.
Could you please elaborate a bit the special use case here?
The table was copied directly from the Reference Manual. We also have listed all supported input and output sample rates just right behind that table. If there're missing rates, we probably should update those two lists also? Otherwise, how could we have a driver limiting both I/O sample rates while we still see something not in the table?
+static int proc_autosel(int Fsin, int Fsout, int *pre_proc, int *post_proc)
Please add some comments to this function to explain what it does, and how it works. And better to rename it to something like "fsl_asrc_sel_proc".
+{
- bool det_out_op2_cond;
- bool det_out_op0_cond;
- det_out_op2_cond = (((Fsin * 15 > Fsout * 16) & (Fsout < 56000)) |
((Fsin > 56000) & (Fsout < 56000)));- det_out_op0_cond = (Fsin * 23 < Fsout * 8);
"detect output option condition"? Please explain a bit or add comments to explain.
- /*
* Not supported case: Tsout>16.125*Tsin, and Tsout>8.125*Tsin.
Could be "unsupported". And it should fit within one line: /* Unsupported case: Tsout > 16.125 * Tsin, and Tsout > 8.125 * Tsin */
*/- if (Fsin * 8 > 129 * Fsout)
*pre_proc = 5;- else if (Fsin * 8 > 65 * Fsout)
*pre_proc = 4;- else if (Fsin * 8 > 33 * Fsout)
*pre_proc = 2;- else if (Fsin * 8 > 15 * Fsout) {
if (Fsin > 152000)*pre_proc = 2;else*pre_proc = 1;- } else if (Fsin < 76000)
*pre_proc = 0;- else if (Fsin > 152000)
*pre_proc = 2;- else
*pre_proc = 1;- if (det_out_op2_cond)
*post_proc = 2;- else if (det_out_op0_cond)
*post_proc = 0;- else
*post_proc = 1;- if (*pre_proc == 4 || *pre_proc == 5)
return -EINVAL;
I think you'd better add some necessary comments here too.
@@ -377,11 +404,17 @@ static int fsl_asrc_config_pair(struct fsl_asrc_pair *pair) ASRCTR_IDRi_MASK(index) | ASRCTR_USRi_MASK(index), ASRCTR_IDR(index) | ASRCTR_USR(index));
- ret = proc_autosel(inrate, outrate, &pre_proc, &post_proc);
- if (ret) {
pair_err("No supported pre-processing options\n");return ret;- }
I think we should do this earlier in this function, once We know the inrate and outrate, instead of having all register being configured then going for an error-out.
Another thing confuses me: so we could have supported sample rates in the list but the hardware might not support some of them because we couldn't calculate their processing options?