Re: [PATCH v4 2/8] irqchip: Add Realtek RTD1295 mux driver

From: Andreas FÃrber
Date: Tue Nov 19 2019 - 15:56:53 EST

Am 19.11.19 um 13:01 schrieb Marc Zyngier:
> On 2019-11-19 02:19, Andreas FÃrber wrote:
>> +static void rtd1195_mux_enable_irq(struct irq_data *data)
>> +{
>> +ÂÂÂ struct rtd1195_irq_mux_data *mux_data =
>> irq_data_get_irq_chip_data(data);
>> +ÂÂÂ unsigned long flags;
>> +ÂÂÂ u32 mask;
>> +
>> +ÂÂÂ mask = mux_data->info->isr_to_int_en_mask[data->hwirq];
>> +ÂÂÂ if (!mask)
>> +ÂÂÂÂÂÂÂ return;
> How can this happen? You've mapped the interrupt, so it exists.
> I can't see how you can decide to fail such enable.

The [UMSK_]ISR bits and the SCPU_INT_EN bits are not (all) the same.

My ..._isr_to_scpu_int_en[] arrays have 32 entries for O(1) lookup, but
are sparsely populated. So there are circumstances such as WDOG_NMI as
well as reserved bits that we cannot enable. This check should be
identical to v3; the equivalent mask check inside the interrupt handler
was extended with "mask &&" to do the same in this v4.

The other question I'll need to dig into, it's been two years since I
wrote that code - first very simple guesswork, then more elaborate
quirks like the above.


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