Re: [PATCH] ASoC: fsl_asrc: Add an option to select internal ratio mode

On Tue, Jun 30, 2020 at 4:09 AM Nicolin Chen nicoleotsuka@gmail.com wrote:

On Mon, Jun 29, 2020 at 09:58:35PM +0800, Shengjiu Wang wrote:

...

The ASRC not only supports ideal ratio mode, but also supports internal ratio mode.

For internal rato mode, the rate of clock source should be divided with no remainder by sample rate, otherwise there is sound distortion.

Add function fsl_asrc_select_clk() to find proper clock source for internal ratio mode, if the clock source is available then internal ratio mode will be selected.

With change, the ideal ratio mode is not the only option for user.

Signed-off-by: Shengjiu Wang shengjiu.wang@nxp.com

...

+static int fsl_asrc_select_clk(struct fsl_asrc_priv *asrc_priv,

•                        struct fsl_asrc_pair *pair,
  

•                        int in_rate,
  

•                        int out_rate)
  

+{

• struct fsl_asrc_pair_priv *pair_priv = pair->private;
  

• struct asrc_config *config = pair_priv->config;
  

• int rate[2], select_clk[2]; /* Array size 2 means IN and OUT */
  

• int clk_rate, clk_index;
  

• int i = 0, j = 0;
  

• bool clk_sel[2];
  

• rate[0] = in_rate;
  

• rate[1] = out_rate;
  

• /* Select proper clock source for internal ratio mode */
  

• for (j = 0; j < 2; j++) {
  

•         for (i = 0; i < ASRC_CLK_MAP_LEN; i++) {
  

•                 clk_index = asrc_priv->clk_map[j][i];
  

•                 clk_rate = clk_get_rate(asrc_priv->asrck_clk[clk_index]);
  

•                   /* Only match a perfect clock source with no remainder */
  
  

...

•                 if (clk_rate != 0 && (clk_rate / rate[j]) <= 1024 &&
  

•                     (clk_rate % rate[j]) == 0)
  

•                         break;
  

•         }
  

•         if (i == ASRC_CLK_MAP_LEN) {
  

•                 select_clk[j] = OUTCLK_ASRCK1_CLK;
  

•                 clk_sel[j] = false;
  

•         } else {
  

•                 select_clk[j] = i;
  

•                 clk_sel[j] = true;
  

•         }
  

• }
  

• /* Switch to ideal ratio mode if there is no proper clock source */
  

• if (!clk_sel[IN] || !clk_sel[OUT])
  

•         select_clk[IN] = INCLK_NONE;
  

Could get rid of clk_set:

    for (j) {
            for (i) {
                    if (match)
                            break;
            }

            clk[j] = i;
    }

    if (clk[IN] == ASRC_CLK_MAP_LEN || clk[OUT] == ASRC_CLK_MAP_LEN)

And it only overrides clk[IN] setting but leaving clk[OUT] to to the searching result. This means that clk[OUT] may be using a clock source other than OUTCLK_ASRCK1_CLK if sel[IN] happens to be false while sel[OUT] happens to be true. Not sure if it is intended...but I feel it would probably be safer to use the previous settings: INCLK_NONE + OUTCLK_ASRCK1_CLK?

ok, will update the patch.

best regards wang shengjiu