linux-kernel - Re: [PATCH V4 06/16] PCI: dwc: Add ext config space capability search API

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Date:   Tue, 23 Apr 2019 15:35:02 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Vidya Sagar <vidyas@...dia.com>
Cc:     lorenzo.pieralisi@....com, robh+dt@...nel.org,
        mark.rutland@....com, thierry.reding@...il.com,
        jonathanh@...dia.com, kishon@...com, catalin.marinas@....com,
        will.deacon@....com, jingoohan1@...il.com,
        gustavo.pimentel@...opsys.com, mperttunen@...dia.com,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kthota@...dia.com,
        mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH V4 06/16] PCI: dwc: Add ext config space capability
 search API

On Tue, Apr 23, 2019 at 01:57:20PM +0530, Vidya Sagar wrote:
> Add extended configuration space capability search API using struct dw_pcie *
> pointer
> 
> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
> Acked-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
> ---
> Changes from [v3]:
> * None
> 
> Changes from [v2]:
> * None
> 
> Changes from [v1]:
> * This is a new patch in v2 series
> 
>  drivers/pci/controller/dwc/pcie-designware.c | 41 ++++++++++++++++++++
>  drivers/pci/controller/dwc/pcie-designware.h |  1 +
>  2 files changed, 42 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 6a98135244d6..ecf5fe8842f6 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -53,6 +53,47 @@ u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap)
>  	return __dw_pcie_find_next_cap(pci, next_cap_ptr, cap);
>  }
>  

Please make sure there's a comment here about why
pci_find_ext_capability() can't be used (a comment covering both this
and pci_find_capability() is fine, if the reason is the same).

> +static int dw_pcie_find_next_ext_capability(struct dw_pcie *pci, int start,
> +					    int cap)
> +{
> +	u32 header;
> +	int ttl;
> +	int pos = PCI_CFG_SPACE_SIZE;
> +
> +	/* minimum 8 bytes per capability */
> +	ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;
> +
> +	if (start)
> +		pos = start;
> +
> +	header = dw_pcie_readl_dbi(pci, pos);
> +	/*
> +	 * If we have no capabilities, this is indicated by cap ID,
> +	 * cap version and next pointer all being 0.
> +	 */
> +	if (header == 0)
> +		return 0;
> +
> +	while (ttl-- > 0) {
> +		if (PCI_EXT_CAP_ID(header) == cap && pos != start)
> +			return pos;
> +
> +		pos = PCI_EXT_CAP_NEXT(header);
> +		if (pos < PCI_CFG_SPACE_SIZE)
> +			break;
> +
> +		header = dw_pcie_readl_dbi(pci, pos);
> +	}
> +
> +	return 0;
> +}
> +
> +int dw_pcie_find_ext_capability(struct dw_pcie *pci, int cap)
> +{
> +	return dw_pcie_find_next_ext_capability(pci, 0, cap);
> +}
> +EXPORT_SYMBOL_GPL(dw_pcie_find_ext_capability);
> +
>  int dw_pcie_read(void __iomem *addr, int size, u32 *val)
>  {
>  	if (!IS_ALIGNED((uintptr_t)addr, size)) {
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 35160b4ce929..67307842e003 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -249,6 +249,7 @@ struct dw_pcie {
>  		container_of((endpoint), struct dw_pcie, ep)
>  
>  u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap);
> +int dw_pcie_find_ext_capability(struct dw_pcie *pci, int 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
>