Re: [PATCH v2 3/3] dwc: PCI: intel: Intel PCIe RC controller driver

[Martin Blumenstingl <martin.blumenstingl@googlemail.com>]

Hi Dilip,

On Mon, Aug 26, 2019 at 8:42 AM Dilip Kota <eswara.kota@linux.intel.com> wrote:
[...]
> intel_pcie_port structure is having "struct dw_pcie" as mentioned below:
>
> struct intel_pcie_port {
>         struct dw_pcie          *pci;
>         unsigned int            id; /* Physical RC Index */
>         void __iomem            *app_base;
>         struct gpio_desc        *reset_gpio;
> [...]
> };
>
> Almost all the drivers are following the same way. I don't see any issue in this way.
> Please help me with more description if you see an issue here.
>
> struct qcom_pcie {
> struct dw_pcie *pci;
> Ref: https://elixir.bootlin.com/linux/v5.3-rc6/source/drivers/pci/controller/dwc/pcie-qcom.c
>
> struct armada8k_pcie {
> struct dw_pcie *pci;
> Ref: https://elixir.bootlin.com/linux/v5.3-rc6/source/drivers/pci/controller/dwc/pcie-armada8k.c
>
> struct artpec6_pcie {
> struct dw_pcie *pci;
> Ref: https://elixir.bootlin.com/linux/v5.3-rc6/source/drivers/pci/controller/dwc/pcie-artpec6.c
>
> struct kirin_pcie {
> struct dw_pcie *pci;
> Ref: https://elixir.bootlin.com/linux/v5.3-rc6/source/drivers/pci/controller/dwc/pcie-kirin.c
>
> struct spear13xx_pcie {
> struct dw_pcie *pci;
> Ref: https://elixir.bootlin.com/linux/v5.3-rc6/source/drivers/pci/controller/dwc/pcie-spear13xx.c
thank you for this detailed list.
it seems that I picked the minority of drivers as "reference" where
it's implemented differently:

first example: pci-meson
  struct meson_pcie {
    struct dw_pcie pci;
    ...
  };

second example: pcie-tegra194 (only in -next, will be part of v5.4)
  struct tegra_pcie_dw {
    ...
    struct dw_pcie pci;
    ...
  };

so some drivers store a pointer pointer to the dw_pcie struct vs.
embedding the dw_pcie struct directly.
as far as I know the result will be equal, except that you don't have
to use a second devm_kzalloc for struct dw_pcie (and thus reducing
memory fragmentation).


Martin