linux-kernel - Re: [PATCH v7 10/10] PCI: imx6: Add i.MX8Q PCIe root complex (RC) support

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Message-ID: <20240721082336.GG1908@thinkpad>
Date: Sun, 21 Jul 2024 13:53:36 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Frank Li <Frank.Li@....com>
Cc: Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	NXP Linux Team <linux-imx@....com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-pci@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v7 10/10] PCI: imx6: Add i.MX8Q PCIe root complex (RC)
 support

On Mon, Jul 08, 2024 at 01:08:14PM -0400, Frank Li wrote:
> From: Richard Zhu <hongxing.zhu@....com>
> 
> Implement i.MX8Q (i.MX8QM, i.MX8QXP, and i.MX8DXL) PCIe RC support. While
> the controller resembles that of iMX8MP, the PHY differs significantly.
> Notably, there's a distinction between PCI bus addresses and CPU addresses.
> 
> Introduce IMX_PCIE_FLAG_CPU_ADDR_FIXUP in drvdata::flags to indicate driver
> need the cpu_addr_fixup() callback to facilitate CPU address to PCI bus
> address conversion according to "ranges" property.
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> Signed-off-by: Frank Li <Frank.Li@....com>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

One comment below.

> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index c72c7a0b0e02d..4e029d1c284e8 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -66,6 +66,7 @@ enum imx_pcie_variants {
>  	IMX8MQ,
>  	IMX8MM,
>  	IMX8MP,
> +	IMX8Q,
>  	IMX95,
>  	IMX8MQ_EP,
>  	IMX8MM_EP,
> @@ -81,6 +82,7 @@ enum imx_pcie_variants {
>  #define IMX_PCIE_FLAG_HAS_PHY_RESET		BIT(5)
>  #define IMX_PCIE_FLAG_HAS_SERDES		BIT(6)
>  #define IMX_PCIE_FLAG_SUPPORT_64BIT		BIT(7)
> +#define IMX_PCIE_FLAG_CPU_ADDR_FIXUP		BIT(8)
>  
>  #define imx_check_flag(pci, val)     (pci->drvdata->flags & val)
>  
> @@ -1015,6 +1017,22 @@ static void imx_pcie_host_exit(struct dw_pcie_rp *pp)
>  		regulator_disable(imx_pcie->vpcie);
>  }
>  
> +static u64 imx_pcie_cpu_addr_fixup(struct dw_pcie *pcie, u64 cpu_addr)
> +{
> +	struct imx_pcie *imx_pcie = to_imx_pcie(pcie);
> +	struct dw_pcie_rp *pp = &pcie->pp;
> +	struct resource_entry *entry;
> +	unsigned int offset;
> +
> +	if (!(imx_pcie->drvdata->flags & IMX_PCIE_FLAG_CPU_ADDR_FIXUP))
> +		return cpu_addr;
> +
> +	entry = resource_list_first_type(&pp->bridge->windows, IORESOURCE_MEM);
> +	offset = entry->offset;
> +
> +	return (cpu_addr - offset);
> +}
> +
>  static const struct dw_pcie_host_ops imx_pcie_host_ops = {
>  	.init = imx_pcie_host_init,
>  	.deinit = imx_pcie_host_exit,
> @@ -1023,6 +1041,7 @@ static const struct dw_pcie_host_ops imx_pcie_host_ops = {
>  static const struct dw_pcie_ops dw_pcie_ops = {
>  	.start_link = imx_pcie_start_link,
>  	.stop_link = imx_pcie_stop_link,
> +	.cpu_addr_fixup = imx_pcie_cpu_addr_fixup,
>  };
>  
>  static void imx_pcie_ep_init(struct dw_pcie_ep *ep)
> @@ -1452,6 +1471,13 @@ static int imx_pcie_probe(struct platform_device *pdev)
>  		if (ret < 0)
>  			return ret;
>  
> +		if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_CPU_ADDR_FIXUP)) {
> +			if (!resource_list_first_type(&pci->pp.bridge->windows, IORESOURCE_MEM)) {
> +				dw_pcie_host_deinit(&pci->pp);
> +				return dev_err_probe(dev, -ENODEV, "DTS Miss PCI memory range");
> +			}

Is this check really necessary? Can the driver work if there is no MEM region
defined in DT (irrespective of the flag)?

I can understand your intentions, but this check seems pointless to me.

- Mani

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