Re: [PATCH v3 7/9] arm64: dts: renesas: rzg3s-smarc-som: Update dma-ranges for PCIe

Geert Uytterhoeven
2025-08-08T12:22:09Z

On Wed, 9 Jul 2025 at 07:05, Biju Das <biju.das.jz@bp.renesas.com> wrote:
> > From: Claudiu Beznea <claudiu.beznea@tuxon.dev>
> > On 07.07.2025 11:18, Biju Das wrote:
> > >> From: Claudiu <claudiu.beznea@tuxon.dev>
> > >> Sent: 04 July 2025 17:14
> > >> Subject: [PATCH v3 7/9] arm64: dts: renesas: rzg3s-smarc-som: Update
> > >> dma-ranges for PCIe
> > >>
> > >> From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
> > >>
> > >> The first 128MB of memory is reserved on this board for secure area.
> > >> Update the PCIe dma-ranges property to reflect this.
> > >
> > > I see R-Car PCIe dma-ranges[1] and [2] maps all possible DDR area supported by the SoC?
> > > Do we need to make board specific as well there?
> >
> > I'm not familiar with R-Car, but if there are ranges reserved for other purposes, I think we should
> > reflect it in board specific device trees.
>
> Already Linux has this DDR info[1]. Linux provides DMA memory only from this region.
>
> In your testing, have you faced any issue like system allocated DMA region other than [1]
> and you don't want to use it, then the changes are ok??

Exactly. PCI memory must be located in the intersection of
dma-ranges in r9a08g045s33.dtsi and the various memory nodes in
rzg3s-smarc-som.dtsi. The latter already excludes the secure area.

> Not sure, PCIe can work on internal memory such as SRAM?

If that is the case, it should be reflected in r9a08g045s33.dtsi.

> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/arch/arm64/boot/dts/renesas/rzg3s-smarc-som.dtsi?h=next-20250708#n31

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds