On Wed, Mar 03, 2021 at 06:51:35PM +0100, Fabrice Gasnier wrote:
> The ARR register is cleared unconditionally upon probing, after the maximum
> value has been read. This initial condition is rather not intuitive, when
> considering the counter child driver. It rather expects the maximum value
> by default:
> - The counter interface shows a zero value by default for 'ceiling'
> attribute.
> - Enabling the counter without any prior configuration makes it doesn't
> count.
>
> The reset value of ARR register is the maximum. So Choice here
> is to backup it, and restore it then, instead of clearing its value.
> It also fixes the initial condition seen by the counter driver.
>
> Fixes: d0f949e220fd ("mfd: Add STM32 Timers driver")
>
> Signed-off-by: Fabrice Gasnier <[email protected]>Acked-by: William Breathitt Gray <[email protected]> > --- > drivers/mfd/stm32-timers.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/mfd/stm32-timers.c b/drivers/mfd/stm32-timers.c > index add6033..44ed2fc 100644 > --- a/drivers/mfd/stm32-timers.c > +++ b/drivers/mfd/stm32-timers.c > @@ -158,13 +158,18 @@ static const struct regmap_config > stm32_timers_regmap_cfg = { > > static void stm32_timers_get_arr_size(struct stm32_timers *ddata) > { > + u32 arr; > + > + /* Backup ARR to restore it after getting the maximum value */ > + regmap_read(ddata->regmap, TIM_ARR, &arr); > + > /* > * Only the available bits will be written so when readback > * we get the maximum value of auto reload register > */ > regmap_write(ddata->regmap, TIM_ARR, ~0L); > regmap_read(ddata->regmap, TIM_ARR, &ddata->max_arr); > - regmap_write(ddata->regmap, TIM_ARR, 0x0); > + regmap_write(ddata->regmap, TIM_ARR, arr); > } > > static int stm32_timers_dma_probe(struct device *dev, > -- > 2.7.4 >
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