Messages in this thread | | | Subject | Re: [PATCH v2 2/3] irqchip: irq-mips-gic: Provide function to map GIC user section | From | Qais Yousef <> | Date | Thu, 15 Oct 2015 10:37:26 +0100 |
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On 10/12/2015 11:16 AM, Thomas Gleixner wrote: > On Mon, 12 Oct 2015, Marc Zyngier wrote: >> On 12/10/15 10:40, Markos Chandras wrote: >>> From: Alex Smith <alex.smith@imgtec.com> >>> >>> The GIC provides a "user-mode visible" section containing a mirror of >>> the counter registers which can be mapped into user memory. This will >>> be used by the VDSO time function implementations, so provide a >>> function to map it in. > <SNIP> > >> This looks much better than the previous version (though I cannot find >> the two other patches on LKML just yet). > Yes, it looks better. But I really have to ask the question why we are > trying to pack the world and somemore into an irq chip driver. We > already have the completely misplaced gic_read_count() there.
This code has a bad history. It was scattered all over the place in arch code. Andrew Bresticker did a good job cleaning it up and moved it to this irqchip driver.
https://lkml.org/lkml/2014/9/18/487 https://lkml.org/lkml/2014/10/20/481
> > While I understand that all of this is in the GIC block at least > according to the documentation, technically it's different hardware > blocks. And logically its different as well.
Yes but they're exposed through the same register interface.
> > So why not describe the various blocks (interrupt controller, timer, > shadow timer) as separate entities in the device tree and let each > subsystem look them up on their own. This cross subsystem hackery is > just horrible and does not buy anything except merge dependencies and > other avoidable hassle.
There's a mips-gic-timer driver in drivers/clocksource. But in device tree it's a subnode of the irqchip driver.
http://lxr.free-electrons.com/source/drivers/clocksource/mips-gic-timer.c http://lxr.free-electrons.com/source/Documentation/devicetree/bindings/interrupt-controller/mips-gic.txt
> > Thoughts? >
It could be refactored but the DT binding already specifies the GIC timer as a subnode of GIC. Exposing this usermode register is the only thing left in the register set that GIC driver wasn't dealing with.
Little gain in changing all of this now I think?
Thanks, Qais
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