Re: [PATCH v10 16/21] irqchip: Add GICv2 specific ACPI boot support

[Jason Cooper]

On Thu, Mar 12, 2015 at 09:46:39AM +0800, Hanjun Guo wrote:
> On 2015/3/12 7:11, Jason Cooper wrote:
> > Hey Grant,
> >
> > On Wed, Mar 11, 2015 at 06:04:50PM +0000, Grant Likely wrote:
> >> On 11 Mar 2015 12:42, "Hanjun Guo" <hanjun.guo@xxxxxxxxxx> wrote:
> >>> From: Tomasz Nowicki <tomasz.nowicki@xxxxxxxxxx>
> >>>
> >>> ACPI kernel uses MADT table for proper GIC initialization. It needs to
> >>> parse GIC related subtables, collect CPU interface and distributor
> >>> addresses and call driver initialization function (which is hardware
> >>> abstraction agnostic). In a similar way, FDT initialize GICv1/2.
> >>>
> >>> NOTE: This commit allow to initialize GICv1/2 basic functionality.
> >>> While now simple GICv2 init call is used, any further GIC features
> >>> require generic infrastructure for proper ACPI irqchip initialization.
> >>> That mechanism and stacked irqdomains to support GICv2 MSI/virtualization
> >>> extension, GICv3/4 and its ITS are considered as next steps.
> >>>
> >>> CC: Jason Cooper <jason@xxxxxxxxxxxxxx>
> >>> CC: Marc Zyngier <marc.zyngier@xxxxxxx>
> >>> CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> >> BTW, Thomas is taking a bit of a break, do he is unlikely to give an ack
> >> here in a timely manner. I've not heard from Jason. Personally, I think we
> >> can proceed without their ack if everything else is in order (heck, I used
> >> to help with the irq subsystem, use me as an ack of you want). The patch is
> >> low impact and only had effect for ARM ACPI builds.
> > I'm not talking much, but I am tracking and collecting everything for irqchip.
> > We do have some other changes in this driver this time around.  So it'd be nice
> > if I could take this.
> >
> > I had reached out to Olof for his thoughts on this and he hasn't had enough
> > cycles to look at it.  iirc, Marc reviewed a previous version and was happy with
> > the changes.  My only question I had for Olof I'll put below:
> 
> Please allow me to explain a little bit before Olof's confirmation, please don't mind if
> any offended.

I'm not sure I parse this correctly, but fwiw, I'm not easily offended.  :-)

> >>> diff --git a/drivers/irqchip/irqchip.c b/drivers/irqchip/irqchip.c
> >>> index 0fe2f71..afd1af3 100644
> >>> --- a/drivers/irqchip/irqchip.c
> >>> +++ b/drivers/irqchip/irqchip.c
> >>> @@ -8,6 +8,7 @@
> >>>   * warranty of any kind, whether express or implied.
> >>>   */
> >>>
> >>> +#include <linux/acpi_irq.h>
> >>>  #include <linux/init.h>
> >>>  #include <linux/of_irq.h>
> >>>  #include <linux/irqchip.h>
> >>> @@ -26,4 +27,6 @@ extern struct of_device_id __irqchip_of_table[];
> >>>  void __init irqchip_init(void)
> >>>  {
> >>>         of_irq_init(__irqchip_of_table);
> >>> +
> >>> +       acpi_irq_init();
> >>>  }
> > Is this in line with Olof's idea that providing a dtb would override ACPI?
> 
> Yes, it will. Since ACPI is default OFF (disabled), if a dtb provided, and no acpi=force
> passed in the early command line, dtb will be used as system configuration for
> boot (dtb is always the prior one for now) [1]. In acpi_gic_init() which called by
> acpi_irq_init(), it will return immediately if acpi disabled, so it will not parse
> any ACPI table for device configuration.

Ok, that matches my recollection.  Thanks for refreshing my memory.  I'll apply
this on a topic branch for irqchip/gic when I return from travel.  Most likely
Friday or over the weekend.

thx,

Jason.
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