ASoC: max98088: fix ni clock divider calculation

[ Upstream commit 6c9762a ]

The ni1/ni2 ratio formula [1] uses the pclk which is the prescaled mclk.
The max98088 datasheet [2] has no such formula but table-12 equals so
we can assume that it is the same for both devices.

While on it make use of DIV_ROUND_CLOSEST_ULL().

[1] https://datasheets.maximintegrated.com/en/ds/MAX98089.pdf; page 86
[2] https://datasheets.maximintegrated.com/en/ds/MAX98088.pdf; page 82

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Link: https://lore.kernel.org/r/20210423135402.32105-1-m.felsch@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

sound/soc/codecs/max98088.c

@@ -41,6 +41,7 @@ struct max98088_priv {
 	enum max98088_type devtype;
 	struct max98088_pdata *pdata;
 	struct clk *mclk;
+	unsigned char mclk_prescaler;
 	unsigned int sysclk;
 	struct max98088_cdata dai[2];
 	int eq_textcnt;
@@ -998,13 +999,16 @@ static int max98088_dai1_hw_params(struct snd_pcm_substream *substream,
        /* Configure NI when operating as master */
        if (snd_soc_component_read(component, M98088_REG_14_DAI1_FORMAT)
                & M98088_DAI_MAS) {
+               unsigned long pclk;
+
                if (max98088->sysclk == 0) {
                        dev_err(component->dev, "Invalid system clock frequency\n");
                        return -EINVAL;
                }
                ni = 65536ULL * (rate < 50000 ? 96ULL : 48ULL)
                                * (unsigned long long int)rate;
-               do_div(ni, (unsigned long long int)max98088->sysclk);
+               pclk = DIV_ROUND_CLOSEST(max98088->sysclk, max98088->mclk_prescaler);
+               ni = DIV_ROUND_CLOSEST_ULL(ni, pclk);
                snd_soc_component_write(component, M98088_REG_12_DAI1_CLKCFG_HI,
                        (ni >> 8) & 0x7F);
                snd_soc_component_write(component, M98088_REG_13_DAI1_CLKCFG_LO,
@@ -1065,13 +1069,16 @@ static int max98088_dai2_hw_params(struct snd_pcm_substream *substream,
        /* Configure NI when operating as master */
        if (snd_soc_component_read(component, M98088_REG_1C_DAI2_FORMAT)
                & M98088_DAI_MAS) {
+               unsigned long pclk;
+
                if (max98088->sysclk == 0) {
                        dev_err(component->dev, "Invalid system clock frequency\n");
                        return -EINVAL;
                }
                ni = 65536ULL * (rate < 50000 ? 96ULL : 48ULL)
                                * (unsigned long long int)rate;
-               do_div(ni, (unsigned long long int)max98088->sysclk);
+               pclk = DIV_ROUND_CLOSEST(max98088->sysclk, max98088->mclk_prescaler);
+               ni = DIV_ROUND_CLOSEST_ULL(ni, pclk);
                snd_soc_component_write(component, M98088_REG_1A_DAI2_CLKCFG_HI,
                        (ni >> 8) & 0x7F);
                snd_soc_component_write(component, M98088_REG_1B_DAI2_CLKCFG_LO,
@@ -1113,8 +1120,10 @@ static int max98088_dai_set_sysclk(struct snd_soc_dai *dai,
         */
        if ((freq >= 10000000) && (freq < 20000000)) {
                snd_soc_component_write(component, M98088_REG_10_SYS_CLK, 0x10);
+               max98088->mclk_prescaler = 1;
        } else if ((freq >= 20000000) && (freq < 30000000)) {
                snd_soc_component_write(component, M98088_REG_10_SYS_CLK, 0x20);
+               max98088->mclk_prescaler = 2;
        } else {
                dev_err(component->dev, "Invalid master clock frequency\n");
                return -EINVAL;