From: "Tanwar, Rahul" <rahul.tanwar@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
tony.luck@intel.com, x86@kernel.org, andriy.shevchenko@intel.com,
alan@linux.intel.com, rppt@linux.ibm.com,
linux-kernel@vger.kernel.org, qi-ming.wu@intel.com,
cheol.yong.kim@intel.com, rahul.tanwar@intel.com
Subject: Re: [PATCH] x86/apic: Update virtual irq base for DT/OF based system as well
Date: Wed, 21 Aug 2019 17:31:20 +0800 [thread overview]
Message-ID: <7b4db9f3-21da-5b5e-e219-0170e812a015@linux.intel.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1908211028030.2223@nanos.tec.linutronix.de>
On 21/8/2019 4:34 PM, Thomas Gleixner wrote:
> Secondly, this link is irrelevant. ioapic_dynirq_base has nothing to do
> with virtual IRQ number 0. It's a boundary for the dynamic allocation of
> virtual interrupt numbers so that the core allocator does not pick
> interrupts out of the IOAPIC's fixed interrupt number space.
>
> This can be legitimately 0 when IOAPIC is not enabled at all.
>
> Can you please explain what kind of problem you were seing and what this
> really fixes?
The problem is that device tree infrastructure considers 0 IRQ value as
invalid/error
value whereas for ACPI, 0 is a valid value. Without this change, the
problem that we
see is that the first driver using of_irq_get_xx() or its variants fails
because of 0 IRQ
number. With this change, allocated IRQ number is never 0 so it works ok.
next prev parent reply other threads:[~2019-08-21 9:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-21 8:13 [PATCH] x86/apic: Update virtual irq base for DT/OF based system as well Rahul Tanwar
2019-08-21 8:34 ` Thomas Gleixner
2019-08-21 9:31 ` Tanwar, Rahul [this message]
2019-08-21 11:20 ` Thomas Gleixner
2019-08-21 12:34 ` Andy Shevchenko
2019-08-21 13:16 ` Thomas Gleixner
2019-08-21 16:47 ` Andy Shevchenko
2019-08-22 3:48 ` Tanwar, Rahul
2019-08-26 11:46 ` [tip: x86/urgent] x86/apic: Fix arch_dynirq_lower_bound() bug for DT enabled machines tip-bot2 for Thomas Gleixner
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