Re: [PATCH 19/19] PCI: Set bridge map_irq and swizzle_irq to default functions

在2022年1月11日一月 下午9:46，Bjorn Helgaas写道：

[-cc many, +cc iproc, loongson, tegra maintainers]

On Tue, Jul 21, 2020 at 08:25:14PM -0600, Rob Herring wrote:

quoted

The majority of DT based host drivers use the default .map_irq() and
.swizzle_irq() functions, so let's initialize the function pointers to
the default and drop setting them in the host drivers.

Drivers like iProc which don't support legacy interrupts need to set
.map_irq() back to NULL.

Probably a dumb question...

This patch removed all the ->swizzle_irq users in drivers/pci/, which
is great -- IIUC swizzling is specified by the PCI-to-PCI Bridge Spec,
r1.2, sec 9.1, and should not be device-specific.  I assume the few
remaining arch/ users (arm and alpha) are either bugs or workarounds
for broken devices.

My question is why we still have a few users of ->map_irq: loongson,
tegra, iproc.  Shouldn't this mapping be described somehow via DT?

Hi all,

For Loongson we are describing IRQ map in DT for newer platforms.
But for legacy platforms (AMD RS780E North Bridge) with i8259 irqchip,
we need to read PCI IRQ registers to get mapping information.

It is not known until boot time, so we have to use map_irq callback.

Thanks.
- Jiaxun

[...]

-- 
- Jiaxun

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