On Fri, Aug 16, 2013 at 10:53:50AM +0200, Sebastian Andrzej Siewior wrote:
> * Zubair Lutfullah | 2013-08-13 17:48:16 [+0100]:
>
> >@@ -316,7 +318,7 @@ static irqreturn_t titsc_irq(int irq, void *dev)
> >
> > if (irqclr) {
> > titsc_writel(ts_dev, REG_IRQSTATUS, irqclr);
> >- am335x_tsc_se_update(ts_dev->mfd_tscadc);
> >+ am335x_tsc_se_set(ts_dev->mfd_tscadc, ts_dev->step_mask);
> > return IRQ_HANDLED;
> > }
> > return IRQ_NONE;
>
> titsc_step_config() computes the mask once since it does not change. It
> is then assigned via am335x_tsc_se_set() to ->reg_se_cache() and later
> always udpated via am335x_tsc_se_update(). This should ensure that ADC's
> and TSC's bits are in sync and clear each other out.
> Now you call am335x_tsc_se_set() in every irq which adds the TSC's mask
> to ->reg_se_cache but why? It was never removed.
>
> Sebastian
The problem is when ADC/TSC are used together.
reg_se_cache would get updated with masks in the se_set function in MFD core.
>From TSC driver, the TSC steps would be set in the reg_se_cache variable.
>From ADC driver, the ADC steps would be set in the reg_se_cache variable.
But the ADC masks weren't being cleared from the reg_se_cache variable
anywhere.
After a while of using ADC/TSC together, the reg_se_cache
variable would have FFFF always. Resulting in redundant sampling
and data in ADC FIFO0.
MFD has received fixes to update the reg_se_cache upon
every call to the se_set functions.
Thus, the step_mask must be set every time to ensure
that it is updated correctly every time.
Hope that clears the confusion.
This TSC/ADC sharing can be pretty confusing.
Thanks
Zubair
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