When SPI clock isn't accurate, 'spi_master_freq' is filled in with expected frequency. Use computed value instead: - e.g. source clock / (CKOUTDIV + 1) Also, current divider may be set to value that makes CKOUT to exceed spi-max-frequency. Rather use lower value (e.g. round up divider when ckout isn't accurate).
Signed-off-by: Fabrice Gasnier <[email protected]> --- drivers/iio/adc/stm32-dfsdm-core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/iio/adc/stm32-dfsdm-core.c b/drivers/iio/adc/stm32-dfsdm-core.c index bf089f5..65b7556 100644 --- a/drivers/iio/adc/stm32-dfsdm-core.c +++ b/drivers/iio/adc/stm32-dfsdm-core.c @@ -243,13 +243,18 @@ static int stm32_dfsdm_parse_of(struct platform_device *pdev, return 0; } - priv->spi_clk_out_div = div_u64_rem(clk_freq, spi_freq, &rem) - 1; + priv->spi_clk_out_div = div_u64_rem(clk_freq, spi_freq, &rem); + + /* round up divider when clkout isn't accurate (e.g. !rem) */ + if (priv->spi_clk_out_div && !rem) + priv->spi_clk_out_div--; + if (!priv->spi_clk_out_div) { /* spi_clk_out_div == 0 means ckout is OFF */ dev_err(&pdev->dev, "spi-max-frequency not achievable\n"); return -EINVAL; } - priv->dfsdm.spi_master_freq = spi_freq; + priv->dfsdm.spi_master_freq = clk_freq / (priv->spi_clk_out_div + 1); if (rem) { dev_warn(&pdev->dev, "SPI clock not accurate\n"); -- 2.7.4
