linux-kernel - Re: [PATCH v12 2/6] PCI: mediatek: Add new method to get shared pcie-cfg base address

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Message-ID: <20210827164634.GA3779223@bjorn-Precision-5520>
Date:   Fri, 27 Aug 2021 11:46:34 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Chuanjia Liu <chuanjia.liu@...iatek.com>
Cc:     robh+dt@...nel.org, bhelgaas@...gle.com, matthias.bgg@...il.com,
        lorenzo.pieralisi@....com, ryder.lee@...iatek.com,
        jianjun.wang@...iatek.com, yong.wu@...iatek.com,
        linux-pci@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 2/6] PCI: mediatek: Add new method to get shared
 pcie-cfg base address

On Mon, Aug 23, 2021 at 11:27:56AM +0800, Chuanjia Liu wrote:
> For the new dts format, add a new method to get
> shared pcie-cfg base address and use it to configure
> the PCIECFG controller

Rewrap this to fill 75 columns.

> Signed-off-by: Chuanjia Liu <chuanjia.liu@...iatek.com>
> Acked-by: Ryder Lee <ryder.lee@...iatek.com>
> ---
>  drivers/pci/controller/pcie-mediatek.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
> index 25bee693834f..4296d9e04240 100644
> --- a/drivers/pci/controller/pcie-mediatek.c
> +++ b/drivers/pci/controller/pcie-mediatek.c
> @@ -14,6 +14,7 @@
>  #include <linux/irqchip/chained_irq.h>
>  #include <linux/irqdomain.h>
>  #include <linux/kernel.h>
> +#include <linux/mfd/syscon.h>
>  #include <linux/msi.h>
>  #include <linux/module.h>
>  #include <linux/of_address.h>
> @@ -23,6 +24,7 @@
>  #include <linux/phy/phy.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/regmap.h>
>  #include <linux/reset.h>
>  
>  #include "../pci.h"
> @@ -207,6 +209,7 @@ struct mtk_pcie_port {
>   * struct mtk_pcie - PCIe host information
>   * @dev: pointer to PCIe device
>   * @base: IO mapped register base
> + * @cfg: IO mapped register map for PCIe config
>   * @free_ck: free-run reference clock
>   * @mem: non-prefetchable memory resource
>   * @ports: pointer to PCIe port information
> @@ -215,6 +218,7 @@ struct mtk_pcie_port {
>  struct mtk_pcie {
>  	struct device *dev;
>  	void __iomem *base;
> +	struct regmap *cfg;
>  	struct clk *free_ck;
>  
>  	struct list_head ports;
> @@ -682,6 +686,10 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
>  		val |= PCIE_CSR_LTSSM_EN(port->slot) |
>  		       PCIE_CSR_ASPM_L1_EN(port->slot);
>  		writel(val, pcie->base + PCIE_SYS_CFG_V2);
> +	} else if (pcie->cfg) {
> +		val = PCIE_CSR_LTSSM_EN(port->slot) |
> +		      PCIE_CSR_ASPM_L1_EN(port->slot);
> +		regmap_update_bits(pcie->cfg, PCIE_SYS_CFG_V2, val, val);
>  	}
>  
>  	/* Assert all reset signals */
> @@ -985,6 +993,7 @@ static int mtk_pcie_subsys_powerup(struct mtk_pcie *pcie)
>  	struct device *dev = pcie->dev;
>  	struct platform_device *pdev = to_platform_device(dev);
>  	struct resource *regs;
> +	struct device_node *cfg_node;
>  	int err;
>  
>  	/* get shared registers, which are optional */
> @@ -995,6 +1004,14 @@ static int mtk_pcie_subsys_powerup(struct mtk_pcie *pcie)
>  			return PTR_ERR(pcie->base);
>  	}
>  
> +	cfg_node = of_find_compatible_node(NULL, NULL,
> +					   "mediatek,generic-pciecfg");

This looks wrong to me.  IIUC, since we start at NULL, this searches
the entire device tree for any node with

  compatible = "mediatek,generic-pciecfg"

but we should only care about the specific device/node this driver
claimed.

Should this be part of the match data, i.e., struct mtk_pcie_soc?

> +	if (cfg_node) {
> +		pcie->cfg = syscon_node_to_regmap(cfg_node);

Other drivers in drivers/pci/controller/ use
syscon_regmap_lookup_by_phandle() (j721e, dra7xx, keystone,
layerscape, artpec6) or syscon_regmap_lookup_by_compatible() (imx6,
kirin, v3-semi).

You should do it the same way unless there's a need to be different.
It's also nice if you can use the same struct member name
("mtk_pcie.cfg") as other drivers.  They're not all consistent, but I
don't see any other "cfg".

> +		if (IS_ERR(pcie->cfg))
> +			return PTR_ERR(pcie->cfg);
> +	}
> +
>  	pcie->free_ck = devm_clk_get(dev, "free_ck");
>  	if (IS_ERR(pcie->free_ck)) {
>  		if (PTR_ERR(pcie->free_ck) == -EPROBE_DEFER)
> -- 
> 2.18.0
>