Re: [PATCH v2] irqchip/qcom-pdc: add support for v3.2 HW

[Maulik Shah (mkshah)]

Hi Neil,

On 8/23/2023 2:21 PM, neil.armstrong@xxxxxxxxxx wrote:
> On 23/08/2023 10:25, Maulik Shah (mkshah) wrote:
> > Hi,
> >
> > On 8/23/2023 1:16 PM, Neil Armstrong wrote:
> > > Hi,
> > >
> > > On 23/08/2023 07:35, Maulik Shah (mkshah) wrote:
> > > > Hi Neil,
> > > >
> > > > @@ -142,8 +163,17 @@ static int qcom_pdc_gic_set_type(struct 
> > > > irq_data *d, unsigned int type)
> > > > >           return -EINVAL;
> > > > >       }
> > > > > -    old_pdc_type = pdc_reg_read(IRQ_i_CFG, d->hwirq);
> > > > > -    pdc_reg_write(IRQ_i_CFG, d->hwirq, pdc_type);
> > > > > +    if (pdc_version < PDC_VERSION_3_2) {
> > > > > +        old_pdc_type = pdc_reg_read(IRQ_i_CFG, d->hwirq);
> > > > > +        pdc_reg_write(IRQ_i_CFG, d->hwirq, pdc_type);
> > > > > +    } else {
> > > > > +        u32 val;
> > > > > +
> > > > > +        val = pdc_reg_read(IRQ_i_CFG, d->hwirq);
> > > > > +        old_pdc_type = val & IRQ_i_CFG_TYPE_MASK;
> > > > > +        pdc_reg_write(IRQ_i_CFG, d->hwirq,
> > > > > +                  pdc_type | (val & IRQ_i_CFG_IRQ_ENABLE));
> > > > > +    }
> > > > While above is correct, i don't think we need version check in 
> > > > qcom_pdc_gic_set_type() as bits 0-2 are always for the type in 
> > > > old/new version as mentioned in v1.
> > > >
> > > > Adding one line after reading old_pdc_type should be good enough.
> > >
> > > Yes I understood, but while looking at the IRQ_i_CFG bits, I wanted 
> > > to keep the original
> > > driver behavior intact by setting remaining bits to 0.
> > >
> > > Adding this single line changes that behavior and keeps bits 3-31
> > > to the default register value, which may have some consequences.
> > >
> > > If you consider it's an ok change, then I'll reduce it to this 
> > > single line.
> > Yes this ok change to have single line and should not have  any 
> > consequences.
>
> I also remember why, it's about the final check:
>
> 184         if (old_pdc_type != pdc_type)
> 185                 irq_chip_set_parent_state(d, 
> IRQCHIP_STATE_PENDING, false);
>
> We need to strip out remaining bits of old_pdc_type of this won't work as
> expected, so I'll change it to :
>
> +       old_pdc_type = pdc_reg_read(IRQ_i_CFG, d->hwirq);
> +       pdc_type |= (old_pdc_type & ~IRQ_i_CFG_TYPE_MASK);
> +       old_pdc_type &= IRQ_i_CFG_TYPE_MASK;
> +       pdc_reg_write(IRQ_i_CFG, d->hwirq, pdc_type);
>
> Is it ok for you ?

No.

        old_pdc_type = pdc_reg_read(IRQ_i_CFG, d->hwirq);

+       pdc_type |= (old_pdc_type & ~IRQ_i_CFG_TYPE_MASK);

Adding above suggested single line is sufficient to make final check 
properly compare both old_pdc_type and new pdc_type, right?

But with your above change, It will end up comparing only bits 0-2 of 
old_pdc_type with updated pdc_type (which just got the other bits (3 to 
31) of IRQ_i_CFG register by the ORing it with old_pdc_type).

Thanks,
Maulik