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Subject: Re: [PATCH v4 2/8] irqchip: Add Realtek RTD1295 mux driver
To:     Marc Zyngier <maz@kernel.org>
Cc:     linux-realtek-soc@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Aleix Roca Nonell <kernelrocks@gmail.com>,
        James Tai <james.tai@realtek.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>
References: <20191119021917.15917-1-afaerber@suse.de>
 <20191119021917.15917-3-afaerber@suse.de>
 <a34e00cac16899b53d0b6445f0e81f4c@www.loen.fr>
From:   =?UTF-8?Q?Andreas_F=c3=a4rber?= <afaerber@suse.de>
Organization: SUSE Software Solutions Germany GmbH
Message-ID: <e98364c5-a859-7981-8ccf-f8e5b5069379@suse.de>
Date:   Tue, 19 Nov 2019 21:56:48 +0100
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Am 19.11.19 um 13:01 schrieb Marc Zyngier:
> On 2019-11-19 02:19, Andreas Färber wrote:
>> +static void rtd1195_mux_enable_irq(struct irq_data *data)
>> +{
>> +    struct rtd1195_irq_mux_data *mux_data =
>> irq_data_get_irq_chip_data(data);
>> +    unsigned long flags;
>> +    u32 mask;
>> +
>> +    mask = mux_data->info->isr_to_int_en_mask[data->hwirq];
>> +    if (!mask)
>> +        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.

Regards,
Andreas

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