Re: [PATCH v5 6/6] PCI: dwc: rcar-gen4: Add support for R-Car X5H PCIe4

[Marek Vasut]

On 9/28/26 11:01 PM, Bjorn Helgaas wrote:
> On Mon, Sep 21, 2026 at 10:27:48PM +0200, Marek Vasut wrote:
> > Add support for R8A78000 (R-Car X5H) PCIe4.
> >
> > This driver previously supported R-Car Gen4 S4/V4H/V4M. PCIe features
> > of R-Car X5H PCIe4 are almost all the same.
> >
> > The controller initialization sequence is slightly different and is
> > factored out into controller specific callbacks, in a manner similar
> > to previous R-Car Gen4 handling.
> >
> > The controller does have a PHY attached to it, but the PHY is operated
> > by a separate PHY driver, the PHY driver instance binding is handled
> > in rcar_gen4_pcie_get_resources() and controlled in the aforementioned
> > controller specific callbacks.
> >
> > The controller driver is deliberately using "renesas,rcar-gen5-pcie4"
> > DT compatible string to discern R-Car X5H PCIe4 controller supported
> > by this driver, from R-Car X5H PCIe6 controller which will most likely
> > use a separate driver.
>
> The gen5/pcie4 usage is confusing.
>
> I often push back on things like "PCIe Gen4" because it's ambiguous
> (does it mean "compliant with base spec r4.0" or "supports 16 GT/s" or
> something else), but it's so widely used to mean transfer rate that
> it's hard to resist, and the best I can hope for is clarification.
>
> But in "renesas,rcar-gen5-pcie4", I don't know what the 5 and the 4
> mean.  Maybe "gen5" refers to some internal R-Car thing, and "pcie4"
> is something like "PCIe Gen4, i.e., 16 GT/s"?

Gen5 refers to R-Car Gen5 (5th R-Car SoC generation).

PCIe4 refers to the PCIe Gen4 core in the R-Car Gen5 SoC. There is also 
PCIe Gen6 core in the same SoC, but that will require a different driver 
and different compatible string.

Since none of this shipped in any kernel version yet, would you prefer 
some sort of rename ? I can send patches.

--
Best regards,
Marek Vasut