On Fri, Jul 17, 2020 at 6:40 PM Arnaud Ferraris arnaud.ferraris@collabora.com wrote:
The current clock selection algorithm might select the same clock for both input and output when, for instance, the output sample rate is a multiple of the input rate.
In that case, both selectable clocks will be multiples of both the input and output sample rates, and therefore the first of these clocks will be selected for both input and output, leading to miscalculation of the dividers for either the input or output side.
Example: Input uses clock A (512kHz) and has a sample rate of 8kHz Output uses clock B (1024kHz) and has a sample rate of 16kHz
In this case, the algorithm will select clock A for both input and output: the input divider will therefore be calculated properly (512 / 8 => 64), but the output divider's value will be only half the expected value (512 / 16 => 32 instead of 1024 / 16 => 64).
(input divider, output divider) = (64, 32) for the same clock source (512kHz) looks no problem. could you explain more detail why (64, 32) can't work?
This patch makes sure it always selects distinct input and output clocks.
There should be no such constraint for this IP, do you have any evidence for we should use distinct input and output clocks?
Signed-off-by: Arnaud Ferraris arnaud.ferraris@collabora.com
sound/soc/fsl/fsl_asrc.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/sound/soc/fsl/fsl_asrc.c b/sound/soc/fsl/fsl_asrc.c index 02c81d2e34ad..de10c208d3c8 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 +618,15 @@ 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]);/* Only match a perfect clock source with no remainder */
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* and make sure the input & output clocks are different*/ 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])) break; }-- 2.27.0