linux-kernel - Re: [PATCH v2 23/26] PCI: designware-ep: Configure RESBAR to advertise the smallest size

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Message-ID: <20190413160053.GI126710@google.com>
Date:   Sat, 13 Apr 2019 11:00:53 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Rob Herring <robh+dt@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Murali Karicheri <m-karicheri2@...com>,
        Jingoo Han <jingoohan1@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-arm-kernel@...s.com
Subject: Re: [PATCH v2 23/26] PCI: designware-ep: Configure RESBAR to
 advertise the smallest size

On Mon, Mar 25, 2019 at 02:04:58PM +0530, Kishon Vijay Abraham I wrote:
> Configure RESBAR capability to advertise the smallest size (1MB) for
> couple of reasons. A) Host side resource allocation of BAR fails for
> larger sizes. B) Endpoint function driver does not allocate memory
> for all supported sizes in RESBAR capability.
> If and when there is a usecase required to add more flexibility using
> RESBAR, this can be revisited.

The #define used in the code below is "REBAR"; maybe spell it out
once and then use REBAR instead of RESBAR?

> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  .../pci/controller/dwc/pcie-designware-ep.c   | 34 +++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 74477ad7467f..0c208b9bda43 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -504,10 +504,32 @@ void dw_pcie_ep_exit(struct dw_pcie_ep *ep)
>  	pci_epc_mem_exit(epc);
>  }
>  
> +static unsigned int dw_pcie_ep_find_ext_capability(struct dw_pcie *pci, int cap)
> +{
> +	u32 header;
> +	int pos = PCI_CFG_SPACE_SIZE;
> +
> +	while (pos) {
> +		header = dw_pcie_readl_dbi(pci, pos);
> +		if (PCI_EXT_CAP_ID(header) == cap)
> +			return pos;
> +
> +		pos = PCI_EXT_CAP_NEXT(header);
> +		if (!pos)
> +			break;
> +	}
> +
> +	return 0;
> +}
> +
>  int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  {
> +	int i;
>  	int ret;
> +	u32 reg;
>  	void *addr;
> +	unsigned int nbars;
> +	unsigned int offset;
>  	struct pci_epc *epc;
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>  	struct device *dev = pci->dev;
> @@ -591,6 +613,18 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  
>  	ep->msix_cap = dw_pcie_ep_find_capability(pci, PCI_CAP_ID_MSIX);
>  
> +	offset = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_REBAR);
> +	if (offset) {
> +		reg = dw_pcie_readl_dbi(pci, offset + PCI_REBAR_CTRL);
> +		nbars = (reg & PCI_REBAR_CTRL_NBAR_MASK) >>
> +			PCI_REBAR_CTRL_NBAR_SHIFT;
> +
> +		dw_pcie_dbi_ro_wr_en(pci);
> +		for (i = 0; i < nbars; i++, offset += PCI_REBAR_CTRL)
> +			dw_pcie_writel_dbi(pci, offset + PCI_REBAR_CAP, 0x0);
> +		dw_pcie_dbi_ro_wr_dis(pci);
> +	}
> +
>  	dw_pcie_setup(pci);
>  
>  	return 0;
> -- 
> 2.17.1
>