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

[Bjorn Helgaas <helgaas@kernel.org>]

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"?

> The R-Car X5H PCIe4 controller embeds HDMA instead of EDMA embedded
> in the R-Car Gen4 PCIe controller, "dw-edma" driver supports both
> DMA variants.
> 
> Endpoint mode is currently not implemented for R-Car Gen5 PCIe4.