linux-kernel - Re: [PATCH v4 1/2] PCI: dwc: Add support for vendor specific capability search

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Message-ID: <20241206161314.GA3101322@bhelgaas>
Date: Fri, 6 Dec 2024 10:13:14 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Shradha Todi <shradha.t@...sung.com>
Cc: linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	manivannan.sadhasivam@...aro.org, lpieralisi@...nel.org,
	kw@...ux.com, robh@...nel.org, bhelgaas@...gle.com,
	jingoohan1@...il.com, Jonathan.Cameron@...wei.com,
	fan.ni@...sung.com, a.manzanares@...sung.com,
	pankaj.dubey@...sung.com, quic_nitegupt@...cinc.com,
	quic_krichai@...cinc.com, gost.dev@...sung.com
Subject: Re: [PATCH v4 1/2] PCI: dwc: Add support for vendor specific
 capability search

On Fri, Dec 06, 2024 at 01:14:55PM +0530, Shradha Todi wrote:
> Add vendor specific extended configuration space capability search API
> using struct dw_pcie pointer for DW controllers.
> 
> Signed-off-by: Shradha Todi <shradha.t@...sung.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 16 ++++++++++++++++
>  drivers/pci/controller/dwc/pcie-designware.h |  1 +
>  2 files changed, 17 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 6d6cbc8b5b2c..41230c5e4a53 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -277,6 +277,22 @@ static u16 dw_pcie_find_next_ext_capability(struct dw_pcie *pci, u16 start,
>  	return 0;
>  }
>  
> +u16 dw_pcie_find_vsec_capability(struct dw_pcie *pci, u8 vsec_cap)

To make sure that we find a VSEC ID that corresponds to the expected
vendor, I think this interface needs to be the same as
pci_find_vsec_capability().  In particular, it needs to take a "u16
vendor" and a "u16 vsec_cap".

(pci_find_vsec_capability() takes an "int cap", but I don't think
that's quite right).

> +{
> +	u16 vsec = 0;
> +	u32 header;
> +
> +	while (vsec = dw_pcie_find_next_ext_capability(pci, vsec,
> +					PCI_EXT_CAP_ID_VNDR)) {
> +		header = dw_pcie_readl_dbi(pci, vsec + PCI_VNDR_HEADER);
> +		if (PCI_VNDR_HEADER_ID(header) == vsec_cap)
> +			return vsec;
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(dw_pcie_find_vsec_capability);
> +
>  u16 dw_pcie_find_ext_capability(struct dw_pcie *pci, u8 cap)
>  {
>  	return dw_pcie_find_next_ext_capability(pci, 0, cap);
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 347ab74ac35a..98a057820bc7 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -476,6 +476,7 @@ void dw_pcie_version_detect(struct dw_pcie *pci);
>  
>  u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap);
>  u16 dw_pcie_find_ext_capability(struct dw_pcie *pci, u8 cap);
> +u16 dw_pcie_find_vsec_capability(struct dw_pcie *pci, u8 vsec_cap);
>  
>  int dw_pcie_read(void __iomem *addr, int size, u32 *val);
>  int dw_pcie_write(void __iomem *addr, int size, u32 val);
> -- 
> 2.17.1
>