lkml.org 
[lkml]   [2022]   [Aug]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 06/12] riscv: dts: allwinner: Add the D1 SoC base devicetree
On Mon, 22 Aug 2022 12:13:42 +0000
<Conor.Dooley@microchip.com> wrote:

Hi,

> On 22/08/2022 12:46, Geert Uytterhoeven wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> >
> > Hi Conor, Andre,
> >
> > On Sun, Aug 21, 2022 at 12:07 PM <Conor.Dooley@microchip.com> wrote:
> >> On 21/08/2022 07:45, Icenowy Zheng wrote:
> >>> 在 2022-08-20星期六的 17:29 +0000,Conor.Dooley@microchip.com写道:
> >>>> On 20/08/2022 18:24, Samuel Holland wrote:
>
> >>>>> This is not feasible, due to the different #interrupt-cells. See
> >>>>> https://lore.kernel.org/linux-riscv/CAMuHMdXHSMcrVOH+vcrdRRF+i2TkMcFisGxHMBPUEa8nTMFpzw@mail.gmail.com/
> >>>>>
> >>>>> Even if we share some file across architectures, you still have to
> >>>>> update files
> >>>>> in both places to get the interrupts properties correct.
> >>>>>
> >>>>> I get the desire to deduplicate things, but we already deal with
> >>>>> updating the
> >>>>> same/similar nodes across several SoCs, so that is nothing new. I
> >>>>> think it would
> >>>>> be more confusing/complicated to have all of the interrupts
> >>>>> properties
> >>>>> overridden in a separate file.
> >>>>
> >>>> Yeah, should maybe have circled back after that conversation, would
> >>>> have been
> >>>> nice but if the DTC can't do it nicely then w/e.
> >>>
> >>> Well, maybe we can overuse the facility of C preprocessor?
> >>>
> >>> e.g.
> >>>
> >>> ```
> >>> // For ARM
> >>> #define SOC_PERIPHERAL_IRQ(n) GIC_SPI n
> >>> // For RISC-V
> >>> #define SOC_PERIPHERAL_IRQ(n) n
> >>> ```
> >>>
> >>
> >> Geert pointed out that this is not possible (at least on the Renesas
> >> stuff) because the GIC interrupt numbers are not the same as the
> >> PLIC's & the DTC is not able to handle the addition:
> >> https://lore.kernel.org/linux-riscv/CAMuHMdXHSMcrVOH+vcrdRRF+i2TkMcFisGxHMBPUEa8nTMFpzw@mail.gmail.com/
> >
> > Without the ability to do additions in DTC, we could e.g. list both
> > interrupts in the macro, like:
> >
> > // For ARM
> > #define SOC_PERIPHERAL_IRQ(na, nr) GIC_SPI na
> > // For RISC-V
> > #define SOC_PERIPHERAL_IRQ(na, nr) nr
>
> Do you think this is worth doing? Or are you just providing an
> example of what could be done?
>
> Where would you envisage putting these macros? I forget the order
> of the CPP operations that are done, can they be put in the dts?
>
> >
> > On Mon, Aug 22, 2022 at 12:52 PM Andre Przywara <andre.przywara@arm.com> wrote:
> >> There are interrupt-maps for that:
> >> sun8i-r528.dtsi:
> >> soc {
> >> #interrupt-cells = <1>;
> >> interrupt-map = <0 18 &gic GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>,
> >> <0 19 &gic GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>,
> >> ....
> >>
> >> sun20i-d1.dtsi:
> >> soc {
> >> #interrupt-cells = <1>;
> >> interrupt-map = <0 18 &plic 18 IRQ_TYPE_LEVEL_HIGH>,
> >> <0 19 &plic 19 IRQ_TYPE_LEVEL_HIGH>,
> >>
> >> then, in the shared .dtsi:
> >> uart0: serial@2500000 {
> >> compatible = "snps,dw-apb-uart";
> >> ...
> >> interrupts = <18>;
> >
> > Nice! But it's gonna be a very large interrupt-map.
>
> I quite like the idea of not duplicating files across the archs
> if it can be helped, but not at the expense of making them hard to
> understand & I feel like unfortunately the large interrupt map is
> in that territory.

Well, I don't know about the Renesas case, but as far as we know the
Allwinner D1 and R528 are using the exact same die, just fused differently.
So expressing this in a common .dtsi sounds very desirable, especially
since a devicetree is an architecture agnostic data structure.

And while it's true that a DT interrupt-map is not for the faint of heart,
I think even the casual reader gets the idea quickly by looking at
it, possibly guided by a comment.
And it doesn't need to be very large. grep counted 32 genuine interrupts
in the current .dtsi file, so I just put those ones needed in. If we need
more IRQs later (quite likely), they are easily added, using copy&paste.

Cheers,
Andre

\
 
 \ /
  Last update: 2022-08-22 14:31    [W:0.129 / U:0.220 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site