Re: [PATCH v2 4/6] PCI: dwc: rcar-gen4: Add a new function pointer for other SoC support

[Bjorn Helgaas <helgaas@kernel.org>]

Include the function pointer name in the subject so it's a little more
specific.

On Tue, Mar 26, 2024 at 11:45:38AM +0900, Yoshihiro Shimoda wrote:
> This driver can reuse other R-Car Gen4 SoC support. However, some
> initializing settings differs between r8a779f0 and others. So, add
> a new function pointer start_link_enable() to support other R-Car
> Gen4 SoC in the future. No behavior changes.

Make it clear here what the new SoC is.  I think it's r8a779f0, but
you have to read the patch and look for the new .compatible string to
figure that out.

> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> ---
>  drivers/pci/controller/dwc/pcie-rcar-gen4.c | 57 +++++++++++++++++++--
>  1 file changed, 52 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-rcar-gen4.c b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
> index 0be760ed420b..a37613dd9ff4 100644
> --- a/drivers/pci/controller/dwc/pcie-rcar-gen4.c
> +++ b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
> @@ -53,9 +53,16 @@ struct rcar_gen4_pcie {
>  	void __iomem *base;
>  	struct platform_device *pdev;
>  	enum dw_pcie_device_mode mode;
> +
> +	int (*start_link_enable)(struct rcar_gen4_pcie *rcar);
>  };
>  #define to_rcar_gen4_pcie(_dw)	container_of(_dw, struct rcar_gen4_pcie, dw)
>  
> +struct rcar_gen4_pcie_platdata {
> +	enum dw_pcie_device_mode mode;
> +	int (*start_link_enable)(struct rcar_gen4_pcie *rcar);

I think it's confusing to repeat "mode" and "start_link_enable" in
both rcar_gen4_pcie and rcar_gen4_pcie_platdata.  I know several other
drivers use this pattern, but I think it is simpler overall to just
save the pointer directly, e.g.,

  imx6_pcie_probe
    imx6_pcie->drvdata = of_device_get_match_data(dev);

  ls_pcie_probe
    pcie->drvdata = of_device_get_match_data(dev);

  tegra_pcie_dw_probe
    data = of_device_get_match_data(dev);
    pcie->of_data = (struct tegra_pcie_dw_of_data *)data;

So I think the best thing would be to add struct
rcar_gen4_pcie_platdata, *move* rcar_gen4_pcie.mode there, and save a
pointer to the rcar_gen4_pcie_platdata in struct rcar_gen4_pcie.

That could be its own separate patch, which is nice on its own because
it gets rid of the (void *) casts in rcar_gen4_pcie_of_match[].

Then add .start_link_enable() (or .ltssm_enable(), see below) and the
r8a779f0 bits in another patch.

> +};
> +
>  /* Common */
>  static void rcar_gen4_pcie_ltssm_enable(struct rcar_gen4_pcie *rcar,
>  					bool enable)
> @@ -123,9 +130,13 @@ static int rcar_gen4_pcie_speed_change(struct dw_pcie *dw)
>  static int rcar_gen4_pcie_start_link(struct dw_pcie *dw)
>  {
>  	struct rcar_gen4_pcie *rcar = to_rcar_gen4_pcie(dw);
> -	int i, changes;
> +	int i, changes, ret;
>  
> -	rcar_gen4_pcie_ltssm_enable(rcar, true);
> +	if (rcar->start_link_enable) {
> +		ret = rcar->start_link_enable(rcar);

This looks basically like what qcom does:

  qcom_pcie_start_link
    if (pcie->cfg->ops->ltssm_enable)
      pcie->cfg->ops->ltssm_enable(pcie)

Can you copy that and use the same name for the pointer and function
name (.ltssm_enable, .*_ltssm_enable())?

> +		if (ret)
> +			return ret;
> +	}
>  
>  	/*
>  	 * Require direct speed change with retrying here if the link_gen is
> @@ -437,7 +448,10 @@ static void rcar_gen4_remove_dw_pcie_ep(struct rcar_gen4_pcie *rcar)
>  /* Common */
>  static int rcar_gen4_add_dw_pcie(struct rcar_gen4_pcie *rcar)
>  {
> -	rcar->mode = (uintptr_t)of_device_get_match_data(&rcar->pdev->dev);
> +	const struct rcar_gen4_pcie_platdata *pd = of_device_get_match_data(&rcar->pdev->dev);
> +
> +	rcar->mode = pd->mode;
> +	rcar->start_link_enable = pd->start_link_enable;
>  
>  	switch (rcar->mode) {
>  	case DW_PCIE_RC_TYPE:
> @@ -500,14 +514,47 @@ static void rcar_gen4_pcie_remove(struct platform_device *pdev)
>  	rcar_gen4_pcie_unprepare(rcar);
>  }
>  
> +static int r8a779f0_pcie_start_link_enable(struct rcar_gen4_pcie *rcar)
> +{
> +	rcar_gen4_pcie_ltssm_enable(rcar, true);

Previously we called rcar_gen4_pcie_ltssm_enable() for
"renesas,rcar-gen4-pcie" and "renesas,rcar-gen4-pcie-ep".  But after
this patch, it looks like we only call it for "renesas,r8a779f0-pcie"
and "renesas,r8a779f0-pcie-ep"?

> +
> +	return 0;
> +}
> +
> +static struct rcar_gen4_pcie_platdata platdata_r8a779f0_pcie = {
> +	.mode = DW_PCIE_RC_TYPE,
> +	.start_link_enable = r8a779f0_pcie_start_link_enable,
> +};
> +
> +static struct rcar_gen4_pcie_platdata platdata_r8a779f0_pcie_ep = {
> +	.mode = DW_PCIE_EP_TYPE,
> +	.start_link_enable = r8a779f0_pcie_start_link_enable,
> +};
> +
> +static struct rcar_gen4_pcie_platdata platdata_rcar_gen4_pcie = {
> +	.mode = DW_PCIE_RC_TYPE,
> +};
> +
> +static struct rcar_gen4_pcie_platdata platdata_rcar_gen4_pcie_ep = {
> +	.mode = DW_PCIE_EP_TYPE,
> +};
> +
>  static const struct of_device_id rcar_gen4_pcie_of_match[] = {
> +	{
> +		.compatible = "renesas,r8a779f0-pcie",
> +		.data = &platdata_r8a779f0_pcie,
> +	},
> +	{
> +		.compatible = "renesas,r8a779f0-pcie-ep",
> +		.data = &platdata_r8a779f0_pcie_ep,
> +	},
>  	{
>  		.compatible = "renesas,rcar-gen4-pcie",
> -		.data = (void *)DW_PCIE_RC_TYPE,
> +		.data = &platdata_rcar_gen4_pcie,
>  	},
>  	{
>  		.compatible = "renesas,rcar-gen4-pcie-ep",
> -		.data = (void *)DW_PCIE_EP_TYPE,
> +		.data = &platdata_rcar_gen4_pcie_ep,
>  	},
>  	{},
>  };
> -- 
> 2.25.1
>