On Thu, Jul 16, 2020 at 05:13:52PM +0200, Arnaud Ferraris wrote:
> The current clock selection algorithm might select the same clock for
> both input and output. This can happen when, for instance, the output
> sample rate is a multiple of the input rate.
What's the issue when selecting the same clock source for both
input and output? Please explain it in the commit logs.
> This patch makes sure it always selects distinct input and output
> clocks.
>
> Signed-off-by: Arnaud Ferraris <arnaud.ferraris@xxxxxxxxxxxxx>
> ---
> sound/soc/fsl/fsl_asrc.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/sound/soc/fsl/fsl_asrc.c b/sound/soc/fsl/fsl_asrc.c
> index 02c81d2e34ad..6d43cab6c885 100644
> --- a/sound/soc/fsl/fsl_asrc.c
> +++ b/sound/soc/fsl/fsl_asrc.c
> @@ -608,8 +608,8 @@ static void fsl_asrc_select_clk(struct fsl_asrc_priv *asrc_priv,
> {
> 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 rate[2], select_clk[2], clk_index[2]; /* Array size 2 means IN and OUT */
> + int clk_rate;
> int i = 0, j = 0;
>
> rate[IN] = in_rate;
> @@ -618,11 +618,12 @@ static void fsl_asrc_select_clk(struct fsl_asrc_priv *asrc_priv,
> /* 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]);
> + clk_index[j] = asrc_priv->clk_map[j][i];
> + clk_rate = clk_get_rate(asrc_priv->asrck_clk[clk_index[j]]);
> /* Only match a perfect clock source with no remainder */
Better to update the comments here as there's a new condition.
> if (clk_rate != 0 && (clk_rate / rate[j]) <= 1024 &&
> - (clk_rate % rate[j]) == 0)
> + (clk_rate % rate[j]) == 0 &&
> + (j == 0 || clk_index[j] != clk_index[j-1]))
clk_index[j - 1]
