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@xxxxxxx> > --- > +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?